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This is to certify that the
thesis entitled

GROWTH AND PHYSIOLOGY OF DECIDUOUS SHADE
TREES AND CONIFERS IN RESPONSE TO CYCLIC
IRRIGATION REGIMES

presented by

AMANDA JO TAYLOR

has been accepted towards fulﬁllment
of the requirements for the

MS. degree in Horticulture

 

Tin) 04M

' Major Professin’s Signature

6/21/2010

 

Date

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5/08 K:IProleoc&PreleIRCIDateDue.indd

 

GROWTH AND PHYSIOLOGY
OF DECIDUOUS SHADE TREES AND CONIFERS
IN RESPONSE TO CYCLIC IRRIGATION REGIMES

By

Amanda Jo Taylor

A THESIS

Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of

MASTER OF SCIENCE

Horticulture

2010

ABSTRACT

GROWTH AND PHYSIOLOGY
OF DECIDUOUS SHADE TREES AND CONIFERS
IN RESPONSE TO CYCLIC IRRIGATION REGIMES

By
Amanda Jo Taylor

Nursery water management is becoming increasingly important as input costs rise and
water use regulations increase. Irrigation regimes consisting of varying combinations of
irrigation rates and cycle frequencies were tested to investigate their effect on the grth
and physiology of PIP-grown conifers and deciduous shade trees. The project consisted
of two studies: 1) examining the effects of cyclic irrigation and reduced irrigation rates on
seven taxa of deciduous shade trees, and 2) examining the effects of cyclic irrigation and
reduced irrigation rates on four conifer species. Growth and physiological responses were
measured throughout two growing seasons and were more responsive to irrigation rate
than cycle frequency. In the ﬁrst study, we found that 50% reductions in daily irrigation
rates produced conifers of similar size to those produced with the typical irrigation rate.
However, the same reduction in the irrigation rate of PIP-grown deciduous shade trees
decreased stem radial grth of most species tested. Applying water in multiple cycles
did not affect tree growth in either study. Of the various methods of calculating WUE,

carbon isotope discrimination was the most sensitive to irrigation regimes.

ACKNOWLEDGMENTS

Thank you to my advisor Bert Cregg for being so understanding and making work
fun. Thanks to the Cregg. family for always making me feel so welcome in their home.
Thank you to my family, who supported me even though they don’t understand what I’m
doing or why I’m doing it. Thanks especially to Christina for talking me down from the j
ledge on more than one occasion. You are the wind beneath the wings.
Thank you, Heutsche family for making sure that I was fed during the many months that I
was writing my thesis and for being so hospitable to Buddy. Thank you, Ted for being ]
unselfish while I was writing and revising and for putting up with me during the process.
This journey would have been less enjoyable if Aaron Warsaw and Nick Pershey were
not around. Aaron — thank you for listening. Nick — thanks for making me laugh (whether
you meant to or not).
Thank you to my committee members, Jeff Andresen and Tom Fernandez, for the

advice.

0.-

 

TABLE OF CONTENTS

LIST OF TABLES ............................................................................................................... v
LIST OF FIGURES .......................................................................................................... vii
INTRODUCTION ............................................................................................................... 1
CHAPTER ONE
LITERATURE REVIEW
Introduction .............................................................................................................. 7
Container nurseries and irrigation ............................................................................ 8
The pot-in-pot production system .......................................................................... 11
Irrigation scheduling .............................................................................................. ll
Overhead irrigation vs. microirrigation ................................................................. l3
Cyclic irrigation ..................................................................................................... 1 5
Water movement through soils and substrates ....................................................... 15
Water application efﬁciency .................................................................................. 17
Leachate ................................................................................................................. 18
Grth response to water-conserving irrigation regimes
Function of water in plant growth .............................................................. 21
Height and caliper response ....................................................................... 22
Biomass production and resource allocation ............................................. 22
Irrigation rate and grth .......................................................................... 24
Physiology of water stress
Basic water stress physiology .................................................................... 25
Water use efﬁciency .................................................................................. 26
Specific leaf area ........................................................................................ 29
Plant nutrient status ................................................................................... 30
Chlorophyll ﬂuorescence ........................................................................... 32
Water potential ........................................................................................... 32
Literature Cited .......................................................................................... 35
CHAPTER TWO
GROWTH AND PHYSIOLOGY OF DECIDUOUS SHADE TREES GROWN UNDER
CYCLIC IRRIGATION
Abstract ................................................................................................................. 46
Introduction ........................................................................................................... 47
Materials and Methods .......................................................................................... 50
Results ................................................................................................................... 57
Discussion .............................................................................................................. 64
Tables ..................................................................................................................... 70
Figures .................................................................................................................... 74
Literature Cited ...................................................................................................... 85

iv

CHAPTER THREE
GROWTH AND PHYSIOLOGY OF CONTAIN ER-GROWN CONIFERS UNDER

CYCLIC IRRIGATION
Abstract ................................................................................................................. 90
Introduction ........................................................................................................... 91
Materials and Methods .......................................................................................... 95
Results ................................................................................................................. 103
Discussion ............................................................................................................ 112
Tables ................................................................................................................... 122
Figures .................................................................................................................. 124
Literature Cited .................................................................................................... 128
CHAPTER FOUR
COMBINED SUMMARY AND CONCLUSIONS
Signiﬁcance of the Study .................................................................................... 138
Results and Ramiﬁcations .........................................................................................
Deciduous Shade Trees ............................................................................ 138
Conifers ................................................................................................... 139
Future Research .................................................................................................. 141
Literature Cited .................................................................................................... 143
APPENDIX 1 ................................................................................................................... 144
APPENDIX 2 ................................................................................................................... 156

LIST OF TABLES

Table 2.1: Summary analysis of variance (ANOVA) for caliper and height growth of
seven taxa of deciduous shade trees grown in #25 containers in a PIP production system
under varying combinations of irrigation rate and cycle frequencies. ............................... 71

Table 2.2: Summary repeated measures analysis of variance (AN OVA) for mid-day
photosynthesis (Amax), leaf stomatal conductance (gs), and WE (Amax/gs) of A.
ﬁeemanii, A. rubrum, Q. rubra, Ulmus ‘Morton’, and Ulmus ‘Morton Glossy’ grown in
#25 containers in a PIP production system under varying combinations of irrigation rate
and cycle frequencies. ........................................................................................................ 72

Table 2.3: Mean mid-day net Erotpsynthesis (Amax; umol-m-zsl), leaf stomatal
conductance (gs; mol HzO'm -s ), and intrinsic water use efﬁciency (WUEi; Amax/gs)
(iSE) of ﬁve taxa of deciduous shade trees grown in #25 containers in a PIP facility
under varying combinations of irrigation rate (low, 1 cm or high, 2 cm) and daily cycle
frequencies (one or four). Means with different letters are statistically different at p50.05.
Data averaged across all sampling dates and irrigation treatments. .................................. 73

Table 2.4: Speciﬁc leaf area (SLA), total leaf area (TLA), foliar N concentration, and
chlorophyll content (CC) of seven taxa of deciduous shade trees grown in #25 containers
under two irrigation rates (low, 1 cm or high, 2 cm) on 27 July 2009. Within columns,
means with different letters are different at p50.05. Data averaged across all cycle
frequencies. ........................................................................................................................ 74

Table 3.1: Summary repeated measures analysis of variance (ANOVA) for mid-day
photosynthesis (Amax), leaf stomatal conductance (gs), and WE (Amax/gs) of single—
needle conifer species (P. glauca var. densata, P. pungens, and A. ﬁaseri) grown in #3 or
#7 containers in a PIP production system under varying combinations of irrigation rate
and cycle frequencies ....................................................................................................... 123

Table 3.2: 2009 mid-day net photqsynthetic rate (Amax; umol-m-Z-SJ) and leaf stomatal
conductance (gs; mol H20-m -s ), and instantaneous water use efﬁciency (WUEi;
Amax/gs) of four species of coniferous trees grown in #3 or #7 containers in a PIP
production system and receiving three or two irrigation rates, respectively. Cycle
frequency x rate interactions were not signiﬁcant within any species, therefore data was
averaged across cycle frequencies and all sampling dates. Means with different letters are
signiﬁcantly different at p50.05. Within species differences are represented by lowercase
letters. Overall differences are represented by uppercase letters. .................................... 124

vi

LIST OF FIGURES

Figure 2.1: Weekly rainfall and reference evapotranspiration (ETo) from Michigan
Automated Weather Network at Michigan State University (MSU) Hancock Turfgrass
Research Center (2008) and MSU Horticulture Teaching and Research Center, East
Lansing, MI. Rainfall deﬁcit = ETo — rainfall. ........................................................................ 75

Figure 2.2: Container capacity and seasonal course of substrate volumetric moisture
content (V WC; %) of a subsarnple of 16 deciduous shade trees grown in #25 containers
in a PIP facility under varying combinations of irrigation rate (low, 1 cm or high, 2 cm)
and daily cycle frequencies (one or four). ......................................................................... 76

Figure 2.3: Stem radial growth (iSE) over the two-year production cycle of seven taxa of
deciduous shade trees grown in #25 containers in a PIP production system under varying

combinations of irrigation rate (low, 1 cm or high, 2 cm) and daily cycle frequencies (one
or four). Effect of cycles was not signiﬁcant. Data averaged across cycles (n=8; * p30.05;
** p50.01). ......................................................................................................................... 77

-2 -1
Figure 2.4: 2009 mid-day leaf stomatal conductance (gs; mol H20-m -s ) of ﬁve taxa
of deciduous shade trees grown in #25 containers in a PIP production system under two
irrigation rates (low, 1 cm or high, 2 cm). Data averaged across both irrigation rates
(n=40) ................................................................................................................................. 78

- -I
Figure 2.5: 2009 mid-day net ahojpsynthetic rate (Amax; umol-m 2-s ), leaf stomatal
conductance (gs; mol H20'm -s ), and instantaneous water use efﬁciency (WUEi;
Amax/gs) of ﬁve taxa of deciduous shade trees grown in #25 containers in a PIP
production system under two irrigation rates (low, 1 cm or high, 2 cm). Effect of cycle
frequency and irrigation rate was not signiﬁcant. Data averaged across both cycle
frequencies (n=40). ............................................................................................................ 79

Figure 2.6: Diurnal courses of stomatal conductance (gs; mol HzO-m 2-s 1) of Acer
ﬁeemam'i and Acer rubrum trees grown in #25 containers in a PIP production system in
2008 and 2009 under varying combinations of inigation rate (low, 1 cm or high, 2 cm)
and cycle frequency (one or four). Data averaged across irrigation rate and cycle
frequency when effect of treatment was not signiﬁcant (n=l6). Means with different
letters are signiﬁcantly different at p50.05. ............................................................................. 80

Figure 2.7: Diurnal course of leaf water potential (MPa) of Quercus rubra trees grown in
#25 containers in a PIP production system in 2008 and 2009 under varying combinations
of inigation rate (low, 1 cm or high, 2 cm) and cycle frequency (one or four). Effect of
cycles was not signiﬁcant at any time. Data averaged across irrigation rate and cycle
frequency when effect of treatment was not signiﬁcant (n=l6). Times when irrigation rate
was signiﬁcant, data averaged across both irrigation cycle frequencies (n=8; * p50.05; **
p300]; **"‘ p50.0001) ....................................................................................................... 81

Figure 2.8: Diurnal course of leaf water potential (MPa) of Acer ﬁ'eemam'i trees grown in
#25 containers in a PIP production system in 2008 and 2009 under varying combinations
of irrigation rate (low, 1 cm or high, 2 cm) and cycle frequency (one or four). Effect of

cycles was not signiﬁcant. Data averaged across irrigation rate and cycle frequency when

vii

effect of treatment was not signiﬁcant (n=1 6). Times when irrigation rate was signiﬁcant,
data averaged across both irrigation cycle frequencies (n=8; * p50.05; ** p50.01). ........ 81

Figure 2.9: A values (%o) (:tSE) of 2009 foliar tissue of ﬁve deciduous shade tree species
grown in #25 containers in a PIP production system under varying combinations of
irrigation rate (low, 1 cm or high, 2 cm) and daily cycle frequencies (one or four) (n=8; *
p_<_0.05; ** p50.01). Effect of cycles was not signiﬁcant in any taxa except A. rubrum, in
those taxa data is averaged across cycle frequencies. In graph of A. rubrum, means with
different letters are statistically different at p50.05. .......................................................... 82

Figure 2.10: A values (%o) (iSE) of 2008 and 2009 wood of Acer rubrum trees grown in
#25 containers in a PIP production system under varying combinations of irrigation rate
(low, 1 cm or high, 2 cm) and daily cycle frequencies (one or four) (n=16; ** p_<_0.01).
Effect of irrigation rate was not signiﬁcant; data averaged across rates ............................ 83

Figure 3.1: Weekly rainfall and reference evapotranspiration (ETo) from Michigan
Automated Weather Network at Michigan State University (MSU) Hancock Turfgrass
Research Center (2008) and MSU Horticulture Teaching and Research Center (2009),
East Lansing, MI. Rainfall deﬁcit = ETo — rainfall. ........................................................ 125

Figure 3.2: Container capacity and seasonal course of substrate volumetric moisture
content (V WC; %) of a subsarnple of 16 coniferous trees grown in #7 containers in a PIP
facility under varying combinations of irrigation rate (1 or 2 cm) and daily cycle
frequencies (one or four) .................................................................................................. 126

Figure 3.3: Stem radial growth (:J:SE) over the two-year production cycle of four
coniferous tree species grown in #7 containers in a PIP production system under varying
combinations of irrigation rate (1 or 2 cm) and daily cycle frequencies (one or four).
Effect of cycles was not signiﬁcant; data averaged across both cycle frequencies (n=8).
Means with different letters are statistically different at p50.05. .................................... 127

Figure 3.4: Diurnal course of mean leaf stomatal conductance (gs; mol HZO-m 2°s 1) and
(:tSE) of A. fraseri trees grown in #7 containers in a PIP production system under two
inigation rates (1, 2, or 3 cm) on three dates. Cycles x rate interactions were not
signiﬁcant, therefore data was averaged across cycles. The high irrigation rate increased
(p50.05) mean diurnal gs only on 5 August 2009 (a=0.05; n=4). .................................. 128

Figure 3.5: Diurnal course of shoot water potential (MPa) (iSE) of A. ﬁaseri trees grown
in #7 containers in a PIP production system under two irrigation rates (1 or 2 cm)
(a=0.05; n=8) on three dates. Cycle frequency x level interaction was not signiﬁcant,
therefore data was averaged across cycles. * indicates signiﬁcance of mean daily shoot
water potential at pS0.05 .................................................................................................. 129

Figure 3.6: Mean (iSE) A values of 2008 and 2009 wood of four coniferous tree species
grown in #7 containers in a PIP production system under varying combinations of
irrigation rate (1 or 2 cm) and daily cycle frequencies (1 or 4) (a=0.05; n=4). ............... 130

End of season mean 2009 N concentration (%; iSE) of foliar samples collected in 2009

four coniferous tree species grown in #3 containers in a PIP production system under
varying combinations of inigation rate (1, 2, or 3 cm) and daily cycle frequencies (1 or

viii

4). Effect of cycles was not signiﬁcant; data averaged across both cycle frequencies
(n=8). Means with different letters are statistically different at pS0.05 ........................... 131

Figure 3.8: End of season 2009 N concentration (%; iSE) of foliar samples from four
coniferous tree species grown in #7 containers in a PIP production system under varying
combinations of irrigation rate (1 or 2 cm) and daily cycle frequencies (1 or 4). Effect of
cycles was not signiﬁcant; data averaged across both cycle frequencies (n=8). Means
with different letters are statistically different at p50.05, ns=not signiﬁcant. ................. 132

Introduction

Water management is a growing concern for aglicultural producers because of a
predicted decrease in water availability, a predicted substantial increase in water cost,
stricter water use regulations, and a growing concern for the environment. The percentage
of US. farms using irrigation increased to 86% in 2008, from 71% in 2003 (NASS,
2008); however, more than 1500 farms stopped irrigating between 2003 and 2008 due to
insufﬁcient ground or surface water supplies (NASS, 2008). In Michigan, 30% of woody
plant producers ranked input costs as their primary or secondary concern for future
production problems (MDA, 2010).

Agriculture is a major contributor of NO3-N to waterways, and groundwater,
which provides drinking water for more than half of the US. population, is at risk
(Cooper, 1993; Nolan et al., 1997). In temperate ecosystems, nitrogen not used by plants
is converted to nitrate in soils, where it is readily leached into the underlying
groundwater. Aquifers are most vulnerable in regions with excessive nitrogen
contributions, porous soils, and a low ratio of woodland to cropland acres (Nolan et al.,
1997). As a result, groundwater in the upper Midwest is expected to experience moderate
to high nitrate contamination (Nolan and Hitt, 2006). Several states have imposed
regulations limiting water consumption and discharge from agricultural operations,
including nurseries, with the remaining states expected to follow suit (Beeson et al.,
2004).

Production of landscape nursery crops in the United States is an intensive land use
that is largely concentrated in several regions of the country, including hydrologically

sensitive areas in western Michigan and northern Ohio. In these regions, production of

1

high-value nursery crops, such as landscape shade trees and container-grown Christmas
trees, is shifting from traditional ﬁeld-growing systems to container production (NASS,
2007; Neal, 2004). In general, irrigation and fertilization of trees in container production
systems is more intensive than in ﬁeld production, creating the potential for increased
environmental impacts. Because fertilizer applications represent a relatively small portion
of production costs, growers may overapply N to ensure maximum growth of high-value
container-grown material (Tyler et al., 1996). Limited container volumes and the low
nutrient and water holding capacities of commonly used, pine bark-based substrates also
contribute to the need for frequent irrigation and N applications and may cause
substantial leaching from containers.

Historically, irrigation practices have been based on anecdotal evidence. Growers
often irrigate excessively in an effort to ensure maximal growth. Irrigation is often
applied only once a day, in the morning hours when there is little risk of sun scorch or
pathogen dispersal and infection. The use of cyclic irrigation, or applying subvolumes of
a plant’s daily water allowance in multiple allotments throughout the day, can increase
irrigation efﬁciency (Ismail et al., 2007; Warren and Bilderback, 2005). Improved
irrigation efﬁciency is one way in which water can be conserved and water quality can be
maintained; however, only water-conserving irrigation regimes which are not detrimental
to crop growth and quality will be implemented by growers.

In the southeastern US, previous studies have documented that cyclic irrigation
can be beneﬁcial to tree growth and physiology; however, there has been little research
testing irrigation methods in the temperate climate of the northern US. The objectives of

this study were to document the effects of water—conserving irrigation regimes on soil

2

moisture ﬂuctuations and the resulting growth and underlying physiological mechanisms
of container-grown coniferous and broadleaf trees. These results will provide a valid
scientiﬁc basis on which irrigation guidelines for growers in the upper Midwest can be

developed.

LITERATURE CITED

Beeson, Jr., R. C., M. A. Arnold, T.E. Bilderback, B. Bolusky, S. Chandler, H.M.
Gramling, J.D. Lea-Cox, J. R. Harris P.J. Klinger, H.M. Mathers, J.M. Ruter, and TH.
Yeager. 2004. Strategic vision of container nursery irrigation in the next ten years.
Journal of Environmental Horticulture 22(2): 113-115.

Cooper, CM. 1993. Biological effects of agriculturaily derived surface water pollutants
on aquatic systems — a review. Journal of Environmental Quality 22:402-408.

Ismail, S.M., K. Ozawa, and N.A. Khondaker. 2007. Inﬂuence of single and multiple
water application timings on yield and water use efficiency in tomato (var. First Power).
Agricultural Water Management 95(2008): 116-122. ‘

MDA. 2010. Generally accepted agricultural and management practices for irrigation
water use. Michigan Department of Agriculture. 15 February 2010.
<http://michigan.gov/documents/MDA_Irrigation_GAAMP_I 2971 0_7.pdf'>.

NASS. 2007. Nursery crops summary 2006. National Agricultural Statistics Service and
United States Department of Agriculture. 12 December 2010.
<http://www.nass.usda.gov/QuickStats/indexbysubject.jsp?Pass_group=Crops+%26+Pla
ns>.

NASS. 2008. 2007 Census of agriculture farm and ranch irrigation survey report.
National Agricultural Statistics Service and United States Department of Agriculture. 20
January 2010.
<http://www.agcensus.usda.gov/Publications/2007/Online_Highlights/Farm_and_Ranch_
Irrigation_Survey/frisO8.pdf>.

Neal, C. 2004. Production systems for small trees and shrubs in New Hampshire.
University of New Hampshire Cooperative Extension. 18 December 2010.
<http://extension.unh.edu/agric/AGNLT/PSSTSNH.htm>.

Nolan, B.T., B.C. Ruddy, K.J. Hitt, and DR. Helsel. 1997. Risk of nitrate in
groundwaters of the United States — a national perspective. Environ. Sci. Technol.
31 :2229-2236.

Nolan, B.T. and K.J. Hitt. 2006. Vulnerability of shallow groundwater and drinking water
wells to nitrate in the United States. Environ. Sci. Technol. 40:7834-7840

Tyler, H.H., S.L. Warren, and TE. Bilderback. 1996. Cyclic irrigation increases
irrigation application efﬁciency and decreases ammonium losses. Journal of
Environmental Horticulture 14(4): 194-198.

Warren, S.L. and TE. Bilderback. 2005. More plant per gallon: Getting more out of your
water. Horttechnology 15(1): 14-18.

CHAPTER ONE

LITERATURE REVIEW

Literature Review

Introduction

Increased water costs, decreased water availability due to increased competition
for water resources with urban areas, and anticipation of stricter water withdrawal and
discharge regulations have caused nursery producers to rethink water use practices
(Beeson et al., 2004). Growers commonly overwater, applying a ﬁxed rate of irrigation
exceeding plant water use; this often results in excessive water withdrawals, leaching of
nutrients and chemicals into surface and ground water. The development of irrigation
programs which conserve water without sacriﬁcing tree grth and quality will allow the
nursery industry to adapt to future water use regulations, increased input costs, and
decreased water availability.

This report reviews research addressing the following topics related to nurseries
and their irrigation practices and plant grth and physiological responses to water
availability.

1. Container nurseries and irrigation
Pot-in-Pot production systems
Irrigation scheduling
Overhead, micro-irrigation, and cyclic irrigation
Movement of water through soils and substrates
Water application efﬁciency
Leaching fraction

2. Growth response to water conserving irrigation regimes

Growth response to cyclic irrigation

Growth response to reduced irrigation rates
3. Physiology of water stress

Basic water stress physiology

Water use efﬁciency

Chlorophyll Fluorescence

Speciﬁc leaf area

Plant nutrition and chlorophyll content

Water potential
Container Nurseries and Irrigation

Nursery production is an economically important sector of the US. agriculture
industry and has grown in recent years. Nationwide, gross receipts of nursery and
greenhouse crops totaled $4.65B in 2006, up 17% from 2003. Deciduous shade trees and
coniferous evergreens accounted for 13% and 12% of all sales, respectively. The
wholesale value of Christmas tree sales totaled $210,532 million in 2006, up more than
15% from 2003. Additionally, the quantity of Christmas trees sold by the 17 producing
states increased 12% in 2006, to 11.6 million, from 10.3 million in 2003 (NASS, 2007).
Within the nursery industry, container production, which demands more water than ﬁeld
production, is becoming more common relative to balled-and-burlapped sales, driven by
a shift in customer preference (N ASS, 2007).
Michigan is one of the top nursery stock producing states, with over 45,000 acres

in production and supporting over 261,000 employees (Hall et al., 2005; NASS, 2007).
Michigan’s nursery industry is the third-ranked sector in state agricultural market value

and represents a substantial source of revenue for the state, contributing 10.8% of total

sales (NASS, 2007). Michigan also ranks third in the United States in cut Christmas tree
production, with over 28,000 acres in production (NASS, 2007). In 2006, 17 million
gallons of water per day (MGD) were withdrawn to irrigate the state’s nursery and
greenhouse crops (MDEQ, 2006).

Even in states with a seemingly endless supply of water, like Michigan, water
availability is a growing concern for plant producers, especially those growing material in
high-cost container production (Haydu and Beeson, 1997; NASS, 2007). In Michigan,
30% of woody plant producers ranked input costs as their primary or secondary concern
for future production problems (MDA, 2010). Several states have imposed regulations
limiting water withdrawal by nurseries (Beeson et al., 2004); in anticipation of stricter
water use regulations, decreasing water availability, and increased cost, nurseries are
seeking water conserving irrigation methods.

Irrigation is crucial to optimizing plant growth and quality in container production
due to the limited storage capacity of containers and the highly porous substrates,
especially at the height of the growing season when plant water demand is at its peak.
The frequent use of pine bark-based substrates in the eastern US. presents growers with
water and nutrient management challenges. The relatively large particle sizes make pine
bark-based substrates highly porous, and therefore low in water and nutrient retention
capacity. To compensate, growers apply high volumes of water and high rates of fertilizer
in an attempt to maximize production. The resulting, and often highly concentrated,
container solution is highly susceptible to leaching (Bilderback, 2001 ). Increasingly,
nurseries are capturing the efﬂuent and reusing it to irrigate (Fain et al., 2000); however,

the quality of recycled water may not be appropriate for crops. Water quality is cited as

the most critical factor in producing container grown plants (Yeager et al., 2007).
Recycling irrigation water and stricter regulation of water quality make water
management a prime concern for growers.

Nurseries can increase irrigation efﬁciency to decrease water use and prevent
leaching of chemicals. On average, daily irrigation rates are between 1.25 and 2.5 cm of
irrigation for container grown woody ornamental plants (Fain et al., 2000; Fare et al.,
1992); however, because irrigation efﬁciency is not regularly monitored (Fain et al.,
2000; Schoene et al., 2006), actual volumes applied can vary greatly. In a study by Fain
et al. (2000), the application thought by growers to be 2.5 cm was actually 1.5 cm, 40%
less than what was assumed.

Several agricultural agencies and horticultural organizations recognize that water
management is an issue and have developed recommendations for their stakeholders. In
an effort to preserve water quality and prevent pollution, Best Management Practices
(BMPs) were developed in 1997 by the Southern Nursery Association (SNA) (Yeager et
al., 2007) to provide guidelines for irrigation practices, capture and reuse of water, and
water use monitoring. Similarly, the Michigan Department of Agriculture (MDA) has
established Generally Accepted Agricultural and Management Practices (GAAMPs) for
irrigation water use to promote stewardship in water management by optimizing water
quantity and quality, soil and plant quality, and yield (MDA, 2010). As the nursery
industry recognizes the need for and shifts toward water-conserving production practices,

alternative, highly efﬁcient production and irrigation techniques are needed.

10

The Pot-in-Pot Production System
The the pot-in-pot (PIP) production system is a method which increases the efficiency of
crop production. Introduced in the 1990’s, PIP production eliminates common problems
associated with conventional above ground (CAG) Container growing. Plants in CAG
production oﬁen suffer from windthrow and require frequent, labor intensive
repositioning, increasing production costs for growers. PIP production eliminates this
problem by anchoring containers in the ground (Adrian et al., 1998). The PIP system uses
two containers; a socket pot, which is sunk into the ground and serves as an anchor, and
the growing pot, which is nested within the socket pot. In the summer when solar
radiation is most intense, substrate temperatures in above ground containers can reach
levels detrimental to plant growth. Containers in the PIP system are insulated by the
surrounding soil, reducing substrate temperature fluctuations and promoting root grth
(Hight and Bilderback, 1993; Ruter, 1997; Zhu et al., 2005). Pot-in-pot production also
offers advantages over ﬁeld production. In PIP production, less damage to roots occurs at
harvest compared to ﬁeld-grown trees, because the root system of a PIP-grown tree is
contained within the pot (Hight and Bilderback, 1993). Field-grown trees can only be
harvested when the ground is not frozen; however, trees grown in the PIP system can be
harvested throughout the year, increasing the sales window in northern climates.
Irrigation Scheduling

Optimizing the timing and duration of irrigation applications is one way in which
nurseries can improve irrigation efﬁciency. Irrigation scheduling, designed to minimize
water use and optimize plant growth and quality, is deﬁned as how much water is applied

and when those applications occur (MDA, 2010). Methods used to schedule irrigation are

11

based on plant response or substrate moisture content, which inﬂuences plant response
(Jones, 2004). Some growers determine irrigation frequency by visually assessing the
status of a crop or an indicator plant, a species of plant that is particularly responsive to
water stress (Schoene et al., 2006); however, the subjectivity of this method can lead to
inadequate irrigation. There remains a need for a simple, ﬂexible, easily adoptable
procedure for irrigation scheduling of container grown woody ornamental species that
does not sacriﬁce plant growth or quality.

Irrigation can be scheduled using evapotranspiration (ET), which is a measure of
plant water demand. ET is the sum of water evaporated and water transpired from a
system. Actual evapotranspiration (ET A) is the evapotranspiration from a given area; in
the case of container production, the container and plant-This is often compared to
potential or reference evapotranspiration (ETo), the evapotranspiration from a reference
crop grown under identical conditions (Beeson, 2005). Typically, that reference crop is
3” high turfgrass. In the 1940's, Penman and Monteith introduced an equation to estimate
ETo from climatic data, taking into account irradiation, relative humidity, wind speed,
and temperature (Penman, 1948; Monteith, 1964).

Modeling the water use of agronomic crops began in the 1940’s when
Thomthwaite (1944) developed a model to predict crop coefﬁcients (Kc)- ET A is species
dependent, calculated as:

ET A = ETO * Kc
Values of Kc, representing the ratio of ETAzETo, are unique to a speciﬁc crop at a
particular growth stage (Beeson, 2005). Since the introduction of the Thomthwaite

model, numerous methods and models have been developed to estimate ET in nursery

12

production from various factors including soil, inigation method, and plant height
(Fitzpatrick, 1980; Bacci et al., 2008).

Actual evapotanspiration is highly correlated with ETO in containerized woody
omamentals, and crop coefﬁcients have been calculated for a number of woody
ornamental species and cultivars (Beeson, 1993; Roberts and Schnipke, 1987; Knox,
1989; Bacci et al., 2008). There was no difference between ETo (calculated using the
Thomthwaite method) and realized plant water demand of ﬁve Acer species grown in
containers, indicating that ETo accurately predicts irrigation requirements of plants
(Roberts and Schnipke, 1987). The use of ET to schedule irrigation of container grown
woody ornamentals has been successful in producing plants of saleable size and quality
(Hill and Allen, 1996), and GAAMP guidelines recommend that growers use ET data and
crop coefﬁcients, when available, to schedule irrigation (MDA, 2010).

There are minimum cumulative ET A values required for plants to reach a
marketable size and quality, indicating that restrictive water applications have the
potential to reduce plant productivity and therefore, proﬁt (Beeson, 2006). Species and
plant size are major determinants of minimum water requirements for containerized
nursery stock (Eakes et al., 1985; Knox, 1989). Species and cultivars of woody
ornamental plants can be grouped into categories of low, moderate, or high water use
(Knox, 1989; Schuch and Burger, 1997; Warsaw et al., 2009a). Container-grown plants
can then be blocked by water use group and irrigated based on plant needs to avoid

under- or overwatering (MDA, 2010).

13

Overhead Irrigation vs. Microirrigation

Water conservation in nurseries can also be achieved by transitioning to a more
efficient irrigation method. In general, container-grown material is irrigated in one of two
ways: overhead through sprinklers or through microsprinklers. Overhead irrigation, the
traditional method used for container production, lacks application efﬁciency. The goal
of daily irrigation in container production is to apply water to the substrate so that it is
available for plant uptake, therefore, applied water that does not enter the container media
is wasted. Overhead irrigation uses sprinklers mounted on risers of varying heights, based
on the size of the plant material. The cylindrical shape of plant containers produces gaps,
in which overhead irrigation water falls, resulting in wasted water. This inevitable off-
target application and resulting low interception efﬁciency and water application
efficiency (WAE) contributes to the low efﬁciency of the system. An increase in
container size (larger diameter) results in larger gaps, and therefore a larger portion of
applied water is lost.

Microirrigation can be used to reduce off-target applications. Microirrigation,
which is commonly used for containers #7 (24.5L) and larger, is a low pressure system
that increases application efficiency by reducing off-target application (Weatherspoon
and Harrell, 1980; Beeson et al., 2004). Microirrigation reduces off-target application of
water, because the emitter is placed close to the media surface and water is applied
directly to the substrate via drip emitters or spray stakes.

The use of microirrigation is increasing in the US, because it uses substantially
less water to increase substrate moisture content relative to overhead irrigation (N ASS,

2007; Weatherspoon and Harrell, 1980). For a given area, installation costs of

14

microirrigation are dependent on container size, whereas those of overhead irrigation
installation are not. Microirrigation is more cost-efﬁcient when growing stock in large
containers because, as container size increases, and quantity of containers per area
decreases, installation costs per area decrease (Haydu and Beeson, 1997).
Cyclic Irrigation

The timing and duration of irrigation events can also be manipulated to improve
production system efﬁciency and water conservation. Cyclic, or pulse, irrigation is a
method by which subvolumes of water are applied in series, in contrast to standard
irrigation which consists of a daily water allotment delivered in one irrigation event.
Cycles consist of water applications separated by rest intervals (time between inigation
events). Intermittent water applications decrease the time averaged application rate
(TAAR), the volume of water applied divided by total time over which it is applied (Zur,
1976). Zur deﬁned TAAR as a function of discharge rate, duration of application, and
length of rest interval (1976). Warren and Bilderback (2005) suggest that TAAR is more
important than the number of irrigation cycles in improving water retention.
Water Movement through Soils and Substrates
To understand how plant growth is affected by cyclic water applications, it must ﬁrst be
understood how water moves through a soil column or, in the case of container growing,
the substrate in a container. Plants require that roots have access to water and oxygen
during the growing season. Plants with insufﬁcient access to soil water or oxygen can
have reduced growth and eventually die; therefore it is desirable to have a balance

between water drainage and retention so that roots have access to both water and oxygen.

15

For this reason, container substrates are often chosen for their water holding and drainage
properties.

The physical characteristics of a substrate and container volume determine how
much water is available for plant uptake (Spomer, 1982). Coarse media, like pine bark
substrate, has low water holding capacity and high leaching potential (Fare et al., 1996).
Secondary components of mixes are also important in determining the leaching potential
of a substrate. Amending pine bark with highly porous material (low water holding
capacity) rather than low porosity components (high water holding capacity) can increase
leaching potential. Fare et al. (1996) reported that pine barkzsand mixes are more porous
than pine barkzpeat media.

Substrate composition also affects the pattern of water distribution in a substrate
column as does the irrigation rate and rest interval, among other factors. During an
irrigation event, water ﬁrst occupies macropores, which offer little physical resistance. If
the duration of the rest interval is sufﬁcient, water will also ﬁll micropores which are
better at storing water for long periods of time than macropores. During the time between
irrigation events, water will drain out of the macropores and progress down the soil
column more easily than out of the micropores, in which water is under greater tension.

Proper manipulation of the timing and duration of irrigation applications can
provide a consistent supply of water to roots. Initially, studies testing cyclic irrigation
were performed on soil (Zur, 1976; Levin and Van Rooyen, 1977). Traditional irrigation
regimes consisting of one continuous application per day can cause an inconsistent
supply of moisture to plant roots and limit grth (Karam et al., 1994); however, cyclic

inigation of soils, if using optimal water volumes, application rates, and rest intervals,

16

’ produces a continuously advancing wetting front, resulting in a consistent wetting
pattern, thus providing consistent water to plant roots (Zur, 1976; Levin and Van Rooyen,
1977)

Lateral movement of water within a substrate column, which is affected by
irrigation regimes, is essential for water retention within container substrates. Cyclic
inigation increases lateral movement of water into soil and decreases the volume lost past
the root zone, compared to single applications (Levin and Van Rooyen, 1977; Levin and
Van Rooyen, 1979). F urthennore, extremely dry pine bark media is resistant to rewetting,
and irrigation of extremely dry containers often results in channeling of water through the
substrate, resulting in increased leaching (Lamack and Niemiera, 1993).

Water Application Efficiency

Nurseries can conserve water by increasing the amount of applied water retained
within the container, therefore reducing effluent. Water application efﬁciency (WAE) is a
measure of how much applied water is retained within the rooting volume of a plant, and
is expressed as:

[(volume applied — volume leached) / volume applied] x 100
Cyclic irrigation has been shown to increase WAE in overhead, spray stake, and drip
irrigation systems (Fare et al., 1994; Karam et al., 1994; Karam and Niemiera, 1994;
Ruter, 1998; Tyler et al., 1996a). Adjusting irrigation rates, volumes and rest intervals
can increase WAE, which generally increases with decreasing TAAR (Lamack and
Niemiera, 1993). Warren and Bilderback (2005) recommend that a target TAAR of less
than 10 mL/minute is needed to increase WAE over that of a single application. Irrigating

cyclically results in an 11 to 38% increase in WAE of pine bark-based substrates

17

(Lamack and Niemiera, 1993; Ruter, 1998; Tyler et al., 1996a). WAE and duration of rest
interval are directly related; however, if the rest interval is too long, pine bark substrate
becomes hydrophobic and resistant to rewetting (Karam and Niemiera, 1994).

Leachate

The leaching fraction (LP) of a container is a measure of how much applied water is lost
by the substrate and is calculated as:

[(volume leached / volume applied)] * 100

Low LFs reduce not only the volume of efﬂuent, but also the amount of nutrients
and chemicals leaving the container and possibly entering waterways. Cyclic irrigation
can reduce leaching fractions regardless of the irrigation system being employed. By
applying water in three cycles instead of one continuous application, volume of container
leachate was reduced by 34% (Fare et al., 1994). Fare et al. (I 996) reduced leachate
volume by 54% when irrigating cyclically versus in one application, regardless of the
length of time between cycles. Using pine barkzsand media and drip irrigation, cyclic
irrigation regimes (2x, 3x or 6x) reduced volume of efﬂuent with no effect on plant
growth of Cotoneaster and Rudbeckia (Tyler et al., 1996a).

Some studies have demonstrated that higher quality plants can be produced with
leaching fractions below the recommended rate; for example, Ligustrum texanum grown
with 0.1 LF had higher foliar concentrations of nitrogen and phosphorus and higher
quality ratings (Jarrell et al., 1983). Owen et al. (2008) found that reducing LF from 0.2
to 0.1 in a pine barkzsand media resulted in 64% reduction in leachate volume and a 64%
reduction in efﬂuent phosphorus concentration without adversely affecting plant dry

weight of Cotoneaster dammeri Schneid. ‘Skogholm’.

18

Time of irrigation applications also inﬂuences LF . Cyclic irrigation including
afternoon applications resulted in decreased LF compared to cycles applied only in the
morning hours (Warren and Bilderback, 2002); however, current Best Management
Practices recommend that water be applied prior to 1000 hours when there is little drift
from wind and low evaporative demand (Yeager et al., 2007).

Electrical Conductivity (EC)

Monitoring the pH and electrical conductivity (EC) of a substrate is important in
managing irrigation and fertilization regimes of container-grown plants. While low LFs
are desirable because they conserve water, the resulting solute accumulation can reduce
plant growth and even be toxic. Past studies have demonstrated that the substrate EC
levels of cyclically irrigated plants are higher than those of plants receiving irrigation in
one cycle (Hicklenton and Cairns, 1995; Fain et al., 1999). Reducing LFs can reduce
growth; for example, reducing LFs from 0.4 and 0.6 to 0 and 0.2 resulted in an 8% and
10% decrease in root and plant dry weight, respectively, of C otoneaster grown in pine
barkzsand media (Tyler et al., 1996b). This trade-off between water conservation and
maximum growth indicates that EC management is essential when employing
intermittent irrigation methods.

PH

The pH of a substance is a measure of its acidity and represents the concentration
of hydrogen ions present. The responses of woody ornamental plants to substrate and
water pH are dependent on species and cultivar as some are more tolerant of pH levels
outside of the optimal range (5 to 6) (Bilderback, 2001) than others. Landis (1990)

reported that the optimum pH level for organic substrates is 5.5, but values of 6 to 8 have

19

been reported at a PIP nursery in Ohio (Zhu et al., 2005). Suboptimal pH levels can alter
uptake of nutrients and reduce plant grth and quality, and the low buffering capacities
of pine bark-peat substrates makes pH monitoring essential in container production
(Mathers, 2007). A classic example is the substitution of hydrogen ions for calcium ions,
an important component in stress signaling. Hydrogen ions can displace calcium ions
from the exchange sites of a soil complex resulting in decreased calcium uptake,
therefore reducing a plant’s ability to adjust to environmental stress. Cyclic irrigation has
not been shown to affect the pH of pine bark substrates (Fain et al., 1999).

Nutrient retention

Excessive irrigation decreases nutrient retention and efﬁcacy (Tyler et al., 1996a;
Tyler et al., 1996b). Nitrogen losses from controlled release fertilizers (CRFs) can reach
80% depending on the nutrient source, release mechanism, and irrigation method (Fare et
al., 1994; Rathier and Frink, 1989). When nutrient retention increases, fewer nutrients are
leached. In addition to reduced irrigation volumes, cyclic irrigation can be used to
increase nutrient retention and decrease the amount of nutrients leaving a container.
Decreases of 47 to 82% in N leached from containers have been recorded when using
cyclic irrigation compared to a single application (Fare et al., 1996; Fain et al., 1999).
The combination of decreased irrigation volume and increased cycle frequency can
reduce the portion of N leached as NO3 -N; for example, the percentage of applied N
leached as NO3-N was 63% when 13 mm was applied in one cycle, but only 15% when 6
mm was applied in three cycles (Fare et al., 1994). Tyler et al. (1996a) suggested that in
order to minimize NH4-N leaching, the duration of the rest interval must be sufﬁcient to

recharge the cation exchange (CEC) of the substrate.

20

Growth response to water-conserving irrigation regimes

Function of water in plant growth
Water is an essential component in plant growth, constituting over 50% of tree fresh
weight. Water uptake is essential for many plant ﬁmctions including maintenance of leaf
temperature and mineral uptake from soils. It is necessary for turgor maintenance and for
cell enlargement, the latter being essential in leaf expansion and grth of tree rings
(Kramer, 1987). Limiting water, or any component of the photosynthesis reaction, can
inhibit carbon assimilation (A), and therefore growth.

Although not the only factor controlling plant productivity, substrate moisture is a
variable which can be relatively easily monitored and manipulated to increase net
photosynthesis and growth. Substrates maintained at or near 100% ﬁeld capacity
maximize growth in a variety of plants, including woody ornamental shrubs (Beeson,
1992). A 23% and 17% increase in shoot dry weight of Acer rubrum ‘Franksred’ trees
occurred when irrigation was applied in three or six cycles, respectively, compared to one
continuous application. This response was similar to that recorded by Timmer and
Armstrong (1989) who observed maximum biomass production of Pinus resinosa
seedlings when container capacity was maintained near 100%. Irrigation regimes
supplying insufﬁcient soil water can signiﬁcantly reduce biomass; for example, substrate
maintained at 73% and 57% container capacity irrigation regimes resulted in 21% and
43% reduction in biomass, respectively, compared to substrate maintained above 92% of

container capacity (Timmer and Armstrong, 1989).

21

Height and Caliper response
Plant responses to cyclic inigation include higher growth index, root growth, trunk
diameter, shoot dry weight, height, and crop yield than plants receiving irrigation in only
one cycle (Beeson and Haydu, 1995; Fain et al., 1999; Ismail et al., 2007; Keever and
Cobb, 1985; Witmer, 2000). Tree caliper and height are of most concern to growers,
because those are the standards by which landscape trees are sold (ANLA, 2004);
therefore, an increase in tree caliper or height translates into more potential proﬁt for the
grower. Increased caliper and height growth of Ulmus alata Michx , Acer rubrum
‘Franksred’, Acer rubrum L. trees, and Quercus acutissima tree species and cultivars in
response to cyclic irrigation has been reported; in some cases, caliper growth was 25%
greater using cyclic irrigation compared to the once-daily irrigation (Beeson and Haydu,
1995; Fain et al., 1999; Witrner, 2000).
Growth responses to irrigation regimes can vary depending on the phase of the
production cycle. Witrner (2000) monitored the response of PIP-produced Acer rubrum
L. ‘Franksred’ trees to cyclic irrigation through a typical two-year production cycle.
Cyclic irrigation (three times daily), as compared to one cycle, increased trunk diameter
of A. rubrum trees only in the second year of production, whereas Acer saccharum Marsh
trees responded similarly in both years of production. These results are consistent with
the ﬁndings of Beeson and Haydn (1995), suggesting that cyclic irrigation may not be
beneﬁcial until roots ﬁll a container, therefore making rapidly growing, large plants more
responsive to cyclic irrigation than slow-growing, small plants (Beeson and Haydu, 1995;

Witrner, 2000).

22

Biomass production and resource allocation

Plants must adjust to water limitations or grth will be reduced and death may
occur (Lopez et al., 2009). Plant responses to short-term water stress include leaf
senescence, growth reduction or cessation, temporary wilting and reduced
photosynthesis, leaf temperature, and ET. Long-term water stress triggers drought
tolerance mechanisms, resulting in increased root mass, leaf senescence, or osmotic
adjustment whereby plants increase intracellular solute concentration (Chaves et al.,
2003).

Responses of plants to water stress are evident not only in total plant mass but
also in its distribution within a plant. Plants allocate biomass in an effort to optimize
resource acquisition such that more mass will be devoted to the organ which is capable of
obtaining the limiting resource; for example, water-stressed plants will increase mass
allocation to below ground structures to obtain water and decrease allocation to above
ground structures to reduce loss of water through stomata (Barbour, 1999). Trees growing
on xeric sites have increased rooting volumes and depths than trees on mesic sites
(Addington et al., 2006); however, most container volumes restrict the rooting space to
less than 1% of that of naturally grown trees of similar size (Gilman and Beeson, 1996).
Therefore, the ability of container-grown plants to increase root mass under limited water
availability is somewhat restricted.

Water applications can be manipulated to manage biomass production and
resource allocation. Plant grth can be manipulated by administering mild drought
stress, which inhibits shoot elongation and keeps plants compact (Cameron et al., 2008).

Conversely, regimes where water is not limiting increase shoot growth and decrease

23

rootzshoot ratios (Beeson and Haydu, 1995; Ruter, 1998). Cyclic irrigation applications
decreased R:S of PIP-produced Prunus x incamp ‘Okame’ trees (Ruter, 1998), and Ulmus
alata Michx. trees grown with cyclic inigation (two or three cycles per day) had more
shoot dry weight than trees receiving one continuous cycle per day (Beeson and Haydu,
1995)

Long-term plant grth can be expressed as a function of cumulative water stress
using the water stress integral CPS). Used in ecological studies as a predictor of tree
growth, ‘I‘S is the cumulative measure of pre-dawn leaf water potential below a deﬁned
threshold (Linder et al., 1987; Myers, 1988). Reducing water stress at any point will
reduce ‘I’S. Container-grown woody ornamental shrubs maintained at higher substrate
moisture contents through cyclic irrigation had lower ‘I’S values than plants receiving one
continuous pre—dawn application (Beeson, 1992). The difference in ‘PS between
cyclically irrigated plants and those receiving a single daily application occurred mainly
between 1300 hr and 1600 hr indicating that cyclic irrigation reduces mid-day water
stress. These ﬁndings are consistent with a study measuring sap ﬂow in A. rubrum L.
‘Franksred’ trees, which demonstrated that afternoon irrigation applications alleviate
mid-day water stress (Witrner, 2000).

The growth rate of woody omarnentals ultimately determines the length of their
production cycle, and shorter production cycles typically increase proﬁtability. Cyclic
microirrigation has been shown to speed up the production process; for example,

Q. virginiana Mill. trees micro-irrigated twice daily reached marketable size nearly three

times faster than those irrigated overhead once daily, and Acer rubrum trees receiving

24

three pulses of irrigation matured 1.82 times faster than similar trees receiving standard

irrigation (Haydu and Beeson, 1997).

25

Irrigation Rate and Growth

Growth response

Daily water use (DWU), equivalent to evapotranspiration + leaching, is an
increasingly popular parameter on which to base irrigation. Regulated deﬁcit inigation
(RDI) is a water conserving method in which only a portion of DWU is applied.
Numerous studies have demonstrated equal or superior growth rates of woody
ornamental crops at reduced irrigation volumes (Groves et al., 1998; Martin et al., 1989;
Roberts and Schnipke, 1987; Warsaw et al., 2009a; Warsaw et al., 2009b). Beeson and
Haydu (1995) summarized that under cyclic inigation the water volume required per area
can be reducedby at least 25% and 50% for xeric or mesic species, respectively, with no
effect on growth (compared to standard overhead irrigation). However, there may be a
trade-off between water conservation and plant productivity if irrigation volume does not
meet plant demand; in a study by Groves et al. (1998), a 40% reduction in applied water
volume resulted in a 10% reduction of maximum growth.
Physiology of water stress

Basic water stress physiology

According to the soil-plant-atmosphere continuum (SPAC), water transport is a
function of water potential (‘1’) of these factors and moves along a gradient of negative
pressure. Reducing plant available water affects plants both directly, by limiting the
amount of water available for photosynthesis and metabolism, and indirectly, by loss of
turgor pressure of the guard cells which reduces stomatal conductance (gs) and therefore

uptake of C02.

26

 

 

 

At low to moderate water stress, a decrease in A is due to reduction in gs (Allen et
al., 2005a; Allen et al., 2005b, Chaves et al., 1991). As water becomes limiting, turgor
pressure within guard cells is reduced, therefore decreasing stomatal aperture, and gs.
Decreases in substrate moisture have been shown to reduce A, gs, and transpiration (E) in
a number of species (N in et al., 2008). Gas exchange rates affect the conversion of
photosynthetically active radiation (PAR) into plant tissue (Allen et al., 2005b).

It has been hypothesized that cyclic irrigation increases growth by removing or
reducing mid-day water limitations, thereby increasing the cumulative time of
photosynthesis (Beeson, 1992; Witrner, 2000). Cyclic irrigation, by maintaining higher
substrate moisture than one continuous application, delays or prevents stomatal closure,
resulting in higher cumulative A (Bilderback, 2002). This response is usually observed in
the afternoon when temperatures are highest. Warren and Bilderback (2002) found that
afternoon irrigation applications were important in maintaining A rates during mid-day
hours. At 1630 HR, plants receiving cyclic applications only in the morning (200, 400,
600 HR and 600, 900, 1200 HR) had A rates 86% less than those of plants receiving
cyclic water applications in the afternoon (1200, 1500, 1800 HR) (Warren and
Bilderback, 2002).

Water Use Efﬁciency ,

Up to 97% of water taken up by a plant is transpired through stomata (Taiz and
Zeiger, 2006), and the initial response to limited water availability is stomatal closure
(Hand et al., 1982; Medrano et al., 2002), which reduces C02 uptake and reduces
assimilation. The relationship between transpiration and assimilation is the water use

efﬁciency (WUE) and can be viewed as a measure of how efﬁciently a plant is using

27

 

water to produce biomass (Anyia and Herzog, 2004). Increases in WUE have been shown
when plant water availability is decreased (Sun et al., 1996). There are three methods
commonly used to calculate WUE: instantaneous WUE (WUEi), integrated WUE, and
transpiration efﬁciency (TE).

Instantaneous W UE

Instantaneous WUE measures WUE at the leaf level, and is the ratio of the rate of
C02 assimilation (measured at the leaf level) ratio to rate of water transpired. It is
calculated using gas exchange data as:

MB or A/gs
Instantaneous WUE excludes water used in respiration and non-photosynthetic ﬁinctions
and is referred to as intrinsic WUE, because the response of E to changes in gs and vapor
pressure deﬁcit (VPD) is inherent to .a species (Bauerle et al., 2006; Bsoul et al., 2007;
Cernusak et al., 2009). Reductions in transpirational losses without concomitant
reductions in A can increase WUEi and lead to substantial long-term increases in WUE
(Yoo et al., 2009).

Integrated W UE

Carbon isotope discrimination (A), using the ratio of intercellular 13C to ”C, is
used to calculate integrated water use efﬁciency, so-called because it provides a
cumulative measure of plant status over the entire life of the plant. Under ideal
conditions, plants discriminate against 13C, the heavier isotope, during photosynthesis
and preferentially incorporate 12C, the lighter isotope, into biomass; however, as water
stress increases, isotope discrimination decreases, and l3C is more readily used,

. . 13 12 . .
increasrng the C: C in plant tissue. Water stress and the subsequent stomatal closure

28

result in increased 13C:12C of tissue relative to non water stressed plants, as intracellular
12C is depleted and 13C is used as a reactant in the photosynthesis (Cregg and Zhang,
2000)

The A calculation is based on the fact that the atmospheric concentration of
13C02 is a known constant, and the 13C: I 2C ratio of plant tissue is less than that of the
atmosphere, indicating that plants discriminate against 13C. This discrimination occurs in
two stages in C3 plants. First, l3C02, the heavier isotope, does not diffuse through
stomata as readily as 12C02. 13C02 diffuses at a rate of 4.4%o that of 12C02. Secondly,
fractionation occurs during carboxylation as Ribulose biphosphate carboxylase-
oxygenase (Rubisco) has a greater afﬁnity for 12C02 than l3C02 by a factor of 27%o
(F arquhar et al., 1989). Standardized A values are adjusted to PeeDee belemnite values
and are expressed as 8 (Craig, 1957). The response of integrated WUE to water stress is
such that as water becomes limiting, A decreases and 5 increases.

T ranspiration Eﬂiciency

Transpiration efﬁciency (TE) is the relationship between water absorbed by a
plant and the total biomass produced and represents the whole plant water use efﬁciency.
This method takes into account water used in other metabolic processes besides
photosynthesis and is calculated as

[biomass produced / water used]

Water-limiting irrigation regimes have been used to increase the TE of a number of plants
including Capsicum annuum L., Catharanthus roseus, and Olea europaea (Bacelar et al.,
2007; Jaleel et al., 2008; Karam et al., 2009). In a study by Ismail et al. (2007), cyclic

irrigation increased TE of tomatoes by 15%.

29

The response of WUE to drought stress is dependent on plant type, species,
cultivar, tree age, provenance, and phenotype, and can be used as a screening process for
selection of drought resistant plants (Adams and Kolb, 2004; Bacelar et al., 2007;
Cernusak et al., 2009; Tumbull et al., 2002; Zhang and Cregg, 2005). In a study of
mature forest trees, Quercus rubra L. trees had higher WUE values when grown on xeric
sites than trees grown under mesic conditions, compared to A. rubrum L. trees which
maintained a low WUE regardless of soil water availability, suggesting that Q. rubra
minimizes transpirational water loss through stomatal regulation allowing for consistent
rates of photosynthesis, whereas A. rubrum does not (Tumbull et al., 2002).

In an effort to gain insight into the functional morphology affecting the WUE
response, models have been developed, which explain that coniferous evergreens are
more resistant to drought stress (increased WUE) than broadleaf trees due to sunken
stomata, ligniﬁed guard cell walls, and lower pre-dawn osmotic potential (an intrinsic
measure of plant resistance to drought). The model also predicts that within coniferous
species, Pinus species are more strongly affected by VPD than other species due to their
low soil to leaf water conductance of xylem tracheids (Gao et al., 2002).

Speciﬁc Leaf A rea

Plants also respond to stress through changes in leaf morphology. Speciﬁc leaf
area (SLA) is the amount of light capturing surface per unit of biomass invested, and can
be viewed as a plant’s return on investment of a leaf (Milla et al., 2008). It is calculated
as:

Leaf area / Leaf mass

30

Thicker, denser leaves have a lower SLA and thinner, less dense leaves have a higher
SLA. Speciﬁc leaf area varies naturally between species, but is also a function of many
environmental factors including temperature, ambient C02 concentration, leaf age, light
intensity, and soil moisture (Milla et al., 2008). Decreases in SLA under water limiting
conditions in plants have been documented in many broadleaf and evergreen trees
including Eucalyptus, Fagus, and Quercus suber (Gouveia and Freitas, 2009; Milla et al.,
2008; Myers and Landsberg, 1989).

Plant nutrient status

The relationship between SLA and photosynthetic response to leaf N can be
expressed as a function of foliar N, such that at a given mass of foliar N, net assimilation
(Amax) increases with rising SLA. Therefore, leaves that are thicker and/or denser will
have a lower photosynthetic rate per unit foliar N resulting in lower AmaSSa whereas
leaves that are thinner and/or less dense will have a higher photosynthetic rate per unit
leaf N and higher Amass (Reich et al., 1998; Tumbull et al., 2002). This response is
independent of environment or genotype (Reich et al., 1998). Response of SLA and N
and Amax relationships are highest in forbs, followed by deciduous species, and lowest in
evergreen species, regardless of leaf type or growth form (Reich et al., 1998).

The response of mass-based A to foliar N levels can also be viewed as a function
of SLA, such that at a speciﬁc SLA, Amax increases with rising foliar N, resulting in
higher Amass- Furthermore, leaves with a lower SLA (thicker, denser leaves) have lower
photosynthetic rates per unit of foliar N (ﬂatter slopes), and therefore lower Amass,

whereas leaves with higher SLA have higher photosynthetic rates per unit of foliar N

(higher slope).

31

Water is an important component of plant nutrient uptake for many reasons.
Controlled release fertilizers, commonly used in container production of woody
ornamental crops, are dependent on water for nutrient release (Fain etal., 2000).
Movement of nutrients into roots is primarily a passive process, as nutrients are taken up
in aqueous solution. Therefore, if the water volume is insufﬁcient, nutrients will not be
taken up, resulting in plant nutrient deﬁciencies; for example, foliar nutrient (N, P, K, Ca,
Mg) concentrations declined with increasing moisture stress in P. resinosa seedlings
(Tirnmer and Armstrong, 1989; Tumbull et al., 2002). Conversely, when excess water is
applied, as is often done in container production, leaching of nutrients can occur, .
therefore reducing the quantities available for plant uptake. Reduced leachate volumes
due to cyclic irrigation regimes increased foliar N concentrations compared to one
continuous application (Karam et al., 1994), and foliar N can be an indicator of
photosynthetic efﬁciency (Allen et al., 2005a;).

Nitrogen is an essential component of chlorophyll. The leaf greenness index,
measured with a portable meter, was developed as a quick, easy, and nondestructive
alternative to sample relative chlorophyll content. The handheld meter measures foliar
absorbance of red and infrared wavelengths and calculates a value representative of the
amount of chlorophyll in the leaf. Leaf greenness index readings have been correlated
with chlorophyll and foliar nitrogen levels in ornamental and agronomic crops (F ritschi
and Rey, 2007; Loh et al., 2002; Wang et al., 2004); however, some studies debate the
validity of SPAD readings as a predictor of leaf N and chlorophyll content, citing leaf
thickness, time, irradiance at time of measurement, and leaf water content as confounding

factors (Marenco et al., 2009; Martinez and Guiamet, 2004; Nigam and Aruna, 2008). In

32

a study of PIP-produced shade trees in the upper Midwest, leaf greenness index was
correlated with assimilation rates and demonstrated a species speciﬁc correlation with
foliar nitrogen (Klooster et al., 2010).

Chlorophyll ﬂuorescence

Chlorophyll ﬂuorescence can be used to test the efﬁciency of photosystems of a
plant (Maxwell and Johnson, 2000). One aspect of chlorophyll ﬂuorescence is Fv/F m,
which indicates the efﬁciency of PSII. Light energy absorbed by plants can be used for
photosynthesis, dissipated as heat, or reradiated as light. These processes are competitive
in that an increase in the quantity of light energy involved in one action dictates a
decrease in the quantity used in the remaining two processes. Measuring the pulse of light
(reradiation) ﬁ'om excited chlorophyll can garner information regarding photosynthesis
and heat release (Maxwell and Johnson, 2000). Drought stress has been shown to
decrease F v/F m (Brodribb and Holbrook, 2003); however, some studies (Havaux, 1992;
Lu and Zhang, 1999) reported a highly drought stress-resistant P811 in species such as
Lycopersicon, Solanum and Tritium species.

Exposure to a stress can confer resistance to other stresses (cross-resistance).
Well-watered plants exposed to subsequent high temperatures have irreversible
reductions in PSII efﬁciency compared to drought stressed plants (Havaux, 1992). This
thermostability is thought to be part of a broader adaptation strategy, as water and
temperature stress often occur simultaneously under ﬁeld conditions.

Water potential

Water potential (‘1’) is a measure of the free energy of water and is the driving

force that transports water from a substrate, through a plant, and into the atmosphere.

33

Water moves from high ‘1’ to low ‘I’ along a gradient of negative pressure. Under drought
stress, ‘P values become increasingly negative, increasing the tension within the xylem
under which the water is held. Stem water potential (WStem) and leaf water potential
(\PLeaf) are the most common measurements of this type. Cavitation (embolism) occurs
when tension falls rises above a species speciﬁc cavitation threshold, and the xylem ﬁlls
with air (Tyree and Sperry, 1989). It has been shown that vascular plants close stomata to
prevent xylem cavitation and the subsequent hydraulic conductance disﬁinction
(Brodribb and Holbrook, 2003). Lethal leaf water potentials (’Plethal) have been
determined for some species including Q. rubra L ("Plethal = -3.34 MPa) and A. rubrum
L (’Plethal = -4.43 MPa).

Leaf hydraulic conductance (Kleaf) is highly correlated with stomatal closure due
to turgor loss and is very sensitive to ‘I’. The ability to repair Kleaf following drought
stress guides gs recovery and is a measure of the vulnerability of a plant’s hydraulic
conductance. It has been suggested that ABA may also play a role in the recovery of gs
(Blackman et al., 2009). The ability to withstand increasing xylem tension may be an
indication of a plant’s ability to adapt to drought (Auge, 1997).

Mid-day ‘I’ is especially of interest in determining physiological responses to
cyclic irrigation. Low mid-day ‘I‘ can be caused by high transpiration rates of plants in
well-watered media or by partially closed stomata in response to drought stress (Reich
and Hinckley, 1989). On average, Q. virginiana Mill trees irrigated with multiple cycles
experienced signiﬁcantly lower ‘PS values than trees irrigated only once daily, indicating

reduced water stress (Beeson and Haydu, 1995).

34

Most of the water taken up by a plant is used in transpirational cooling, so as ‘P
values decreases, so too does the plant’s ability to dissipate heat. It has been suggested
that the grth increase associated with cyclic irrigation is partially due to a decrease in
mid-day water stress as elevated substrate moisture levels allow water transport to leaves,
where latent heat can be absorbed, therefore decreasing the heat load (Beeson and Haydu,
1995). Keever and Cobb (1985) reported that applying pulses of water in the early
afternoon, when temperatures are greatest, resulted in average decreases in daily canopy
temperatures of 44°C in ‘Hershey’s Red’ azalea (Rhododendron x ‘Hershey’s Red’) .

F urtherrnore, high root zone temperatures reduced gs and ‘I’ and decreased root and shoot
growth of A. rubrum trees (Graves et al., 1989).

Nursery growers in the upper Midwest are in need of scientiﬁcally based irrigation
guidelines. A better understanding of the growth and physiological responses of PIP-
grown trees to water-conserving irrigation regimes is needed to develop these guidelines.
By applying traditional ecological sampling methods to horticultural studies, we can gain

insight into the physiological mechanisms governing plant growth responses.

35

LITERATURE CITED

Adams, H. D. and T. E. Kolb. 2004. Drought responses of conifers in ecotone forests of
northern Arizona: tree ring growth and leaf 13C. Oecologia 140: 217-225.

Addington, R.N., Donovan, L. A., Mitchell, R. J ., Vose, J. M., Pecot, S. D., Jack, S. B.,
Hacke, U. G., Sperry, J. S., and R. Oren. 2006. Adjustments in hydraulic architecture of
Pinus palustris maintain similar stomatal conductance in xeric and mesic habitats. Plant,
Cell and Environment 29:53 5—545.

Adrian, J. L., C. C. Montgomery, et al. 1998. Cost Comparisons for Inﬁeld, Above
Ground Container and Pot-in-Pot Production Systems. Journal of Environmental
Horticulture 16(2): 65-68.

Allen, C. B., R. E. Will, and MA. Jacobson. 2005a. Production efﬁciency and radiation
use efﬁciency of four tree species receiving irrigation and fertilization. Forest Science
51(6): 556-569. , ‘

Allen, C. B., R. E. Will, R.C. McGarvey, D.R. Coyle, and MD. Coleman. 2005b.
Radiation-use efﬁciency and gas exchange responses to water and nutrient availability in
irrigated and fertilized stands of sweetgum and sycamore. Tree Physiology 25(2): 191-
200.

AN LA. 2004. American Standard for Nursery Stock. American Nursery and Landscape
Association. ANSI 2601-2004. 129 pp.

Anyia, A.O. and H. Herzog. 2004. Water use efﬁciency, leaf area, and leaf gas exchange
of cowpeas under mid-season drought. Europ. J. Agronomy 20:327-339.

Auge, R.M., X. Duan, J .L. Croker, W.T. Witte, and CD. Green. 1998. Foliar dehydration
tolerance of twelve deciduous tree species. Journal of Experimental Botany 49(321) 753-
759.

Bacci, L., Battista, P., and B. Rapi. 2008. An integrated method for irrigation scheduling
of potted plants. Scientia Horticulturae l 16:89-97.

Bacelar E.A., J.M. Moutinho-Pereira, B.C. Goncalves, H.F. Ferreira, and CM. Correia.
2007. Changes in growth, gas exchange, xylem hydraulic properties and water use
efﬁciency of three olive cultivars under contrasting water availability regimes.
Environmental and Experimental Botany 60: 1 83—192.

Barbour, E. 1999. Terrestrial Plant Ecology - Third Edition, Benjamin-Cummings, Menlo
Park, CA.

36

Bauerle, W. L., W. W. Inman, and IE. Dudley. 2006. Leaf abscisic acid accumulation in
response to substrate water content: Linking leaf gas exchange regulation with leaf
abscisic acid concentration. Journal of the American Society for Horticultural Science

131(2): 295-301.

Beeson, Jr., RC. 1992. Restricting overhead irrigation to dawn limits growth in
container-grown woody omamentals. Hortscience 27(9): 996-999.

Beeson, Jr., RC. 1993. Relationship of potential evapotranspiration and actual
evapotranspiration of Rhododendron sp. 'Formosa'. Proceedings of the Florida State
Horticultural Society 106: 274-276.

Beeson, Jr., RC. 2005. Modeling irrigation requirements for landscape omamentals.
Horttechnology 15(1): 18-22.

Beeson, Jr., R. C. 2006. Relationship of plant growth and actual evapotranspiration to
irrigation frequency based on management allowed deﬁcits for container nursery stock.
Journal of the American Society for Horticultural Science 131(1): 140-148.

Beeson, Jr., R. C., M. A. Arnold, T.E. Bilderback, B. Bolusky, S. Chandler, H.M.
Gramling, J .D. Lea-Cox, J. R. Harris P.J. Klinger, H.M. Mathers, J .M. Ruter, and TH.
Yeager. 2004. Strategic vision of container nursery inigation in the next ten years.
Journal of Environmental Horticulture 22(2): 113-115.

Beeson, Jr., R. C. and J. Haydu 1995. Cyclic microirrigation in container-grown
landscape plants improves plant grth and water conservation. Journal of
Environmental Horticulture 13(1): 6-1 1.

Bilderback, TE. 2001. Environmentally compatible container plant production practices.
Proc. Int. Symp. on Growing Media & Hydroponics. Acta Hort. 548. International
Society of Horticultural Science.

Blackman, C. J ., T. J. Brodribb, and GI. Jordan. 2009. Leaf hydraulics and drought
stress: response, recovery and survivorship in four woody temperate plant species. Plant,
Cell and Environment 32(11): 1584-1595.

Brodribb, T. J. and N. M. Holbrook. 2003. Stomatal closure during leaf dehydration,
correlation with other leaf physiological traits. Plant Physiology 132(4): 2166-2173.

Bsoul, E., R. St Hilaire, and D.M. VanLeeuwen. 2007. Bigtooth maples ﬁ'om selected
provenances effectively endure deﬁcit irrigation. Hortscience 42(5): 1167-1173.

Cameron, R., R. Harrison-Murray, M. Fordham, S. Wilkinson, W. Davies, C. Atkinson,
and M. Else. 2008. Regulated irrigation of woody omamentals to improve plant quality
and precondition against drought stress. Annals of Applied Biology 153: 49—61.

37

Cernusak, L. A., K. Winter, and BL. Turner. 2009. Physiological and isotopic (delta13C
and delta180) responses of three tropical tree species to water and nutrient availability.
Plant, Cell and Environment 32(10): 1441-1455.

Chaves, M. M. 1991. Effects of water deﬁcits on carbon assimilation. Journal of
Experimental Botany 42(234): 1-16.

Chaves, M. M., J. P. Maroco, and J .S. Pereira. 2003. Understanding plant responses to
drought - from genes to the whole plant. Functional Plant Biology 30(3): 239-264.

Craig, H. 1957. Isotopic standards for carbon and oxygen and correction factors for mass-
spectrometric analysis of carbon dioxide. Geochimica Et Cosmochimica Acta 12(1-2):
133-149.

Cregg, B. and J. Zhang (2000). Carbon isotope discrimination as a tool to screen for
improved drought tolerance. Proceedings of the 11th Metropolitan Tree Improvement
Alliance (METRIA) Conference, Gresham, OR.

Bakes, D. J ., C.H. Gilliam, H.G. Ponder, W.B. Webster, C.E. Evans and C. Pounders.
1985. Inﬂuence of trickle irrigation on six ﬁeld-grown woody landscape species based on
net evaporation. Journal of Environmental Horticulture 3(3): 139-142.

Fain, G. B., K.M. Tilt, C.H. Gilliam, H.G. Ponder, and J .L. Sibley. 1999. Cyclic
irrigation improves irrigation application efﬁciency and growth of sawtooth oak. Journal
of Arboriculture 25(4): 200-203.

Fain, G. B., C. H. Gilliam, K.M. Tilt, J .W. Olive, and B. Wallace. 2000. Survey of best
management practices in container production nurseries. Journal of Environmental
Horticulture 18(3): 142-144.

Fare, D. C., CH. Gilliam, G.J. Keever, and RB. Reed. 1996. Cyclic irrigation and media
affect container leachate and ageratum growth. Journal of Environmental Horticulture
14(1): 17-21.

Fare, D. C., C. H. Gilliam, and OJ. Keever. 1992. Monitoring irrigation at container
nurseries. HortTechnology 2(1): 75-78.

Fare, D. C., C. H. Gilliam, G.J. Keever, and J .W. Olive. 1994. Cyclic irrigation reduces
container leachate nitrate-nitrogen concentration. Hortscience 29(12): 1514-1517.

Farquhar, G. D., R. Ehleringer, and K. T. Hubic. 1989. Carbon isotope discrimination and
photosynthesis. Annu. Rev. Plant Physiol. Plant Mol. Bio 40: 503-537.

Fitzpatrick, G. 1980. Water budget determinations for container-grown ornamental
plants. Proc. Fla. State Hort. Soc. 93:166-168. 1980.

38

Fritschi, F.B. and J .D. Ray. 2007. Soybean leaf nitrogen, chlorophyll content, and
chlorophyll a/b ratio. Photosynthetica 45(1):92-98.

Gao, Q., P. Zhao, X. Zeng, X. Cai, and W. Shen. 2002. A model of stomatal conductance
to quantify the relationship between leaf transpiration, microclimate and soil water stress.
Plant, Cell and Environment 25: 1373-1381.

Gilman, BF. and RC. Beeson, Jr. 1996. Nursery production method affects root growth.
Journal of Environmental Horticulture 14(2):88-91.

Gouveia, A.C. and H. F reitas. 2009. Modulation of leaf attributes and water use
efﬁciency in Quercus suber along a rainfall gradient. Trees 23:267—275.

Graves, W. R., M. N. Dana, and R]. Joly. 1989. Root-zone temperature affects water
status and growth of red maple. Journal of the American Society for Horticultural Science
114(3): 406-410.

Groves, K. M., S. L. Warren, and TE. Bilderback. 1998. Irrigation volume, application,
and controlled-release fertilizers: I. Effect on plant grth and mineral nutrient content in
containerized plant production. Journal of Environmental Horticulture 16(3): 176-181.

Hall, C.R., A.W. Hodges, and J.J. Haydu. 2005. Economic impacts of the green industry
in the United States. 2 January 2009.
<http://www.ufei.org/ﬁles/pubs/EconomicImpactsoftheUSGreen%201ndustr%28NUCFA
Cﬁnalreport%29.pdf>.

Hand, M. J ., E. Young, and A.C. Vanconcelos. 1982. Leaf water potential, stomatal
resistance, and photosynthetic response to water stress in peach seedlings. Plant
Physiology 69: 1051-1054.

Havaux, M. 1992. Stress Tolerance of Photosystem 11 in Vivo Antagonistic Effects of
Water, Heat, and Photoinhibition Stresses. Plant Physiol. 100:424-432.

Haydu, J. J. and R. C. Beeson, Jr., RC. 1997. Economic feasibility of micro-irrigating
container-grown landscape plants. Journal of Environmental Horticulture 15(1): 23-29.

Hicklenton, P. R. and K. G. Cairns. 1995. Plant water relations and mineral nutrition of
containerized nursery plants in relation to irrigation method. Canadian Journal of Plant
Science 76: 155-160.

Hight, A. and T. E. Bilderback. 1993. Substrate temperatures in above- and below-ground

containers in a pot-in-pot system. Proceedings of the Southern Nursery Association
Conference 39: 113-115.

39

Hill, R. W. and R. G. Allen. 1996. Simple irrigation scheduling calendars. Journal of
Irrigation and Drainage Engineering-Asce 122(2): 107-111.

Ismail, S.M., K. Ozawa, and N.A. Khondaker. 2007. Inﬂuence of single and multiple
water application timings on yield and water use efﬁciency in tomato (var. First Power).
Agricultural Water Management 95(2008): 116-122.

Jaleel, C.A., R. Gopi, B. Sankar, M. Gomathinayagam, and R. Panneerselvarn. 2008.
Differential responses in water use efﬁciency in two varieties of Catharanthus roseus
under drought stress. Comptes Rendus Biologies 331(1): 42-47.

Jarrell, W.M., S. J. Whaley, and B. Miraftabi. 1983. Slow-release fertilizer and water
management with container-grown Ligustrum texanum. Scientia Horticulturae 19(1-2):
1 77-1 90.

Jones, H. G. 2004. Irrigation scheduling: advantages and pitfalls of plant-based methods.
Journal of Experimental Botany, Water-Saving Agriculture Special Issue 55(407): 2427-
2436.

Karam, N.S., A.X. Niemiera, and CE. Leda. 1994. Cyclic sprinkler irrigation and
container substrate affects water distribution and marigold growth. Journal of
Environmental Horticulture 12(4): 208-211.

Karam, NS. and A.X. Niemiera. 1994. Cyclic sprinkler irrigation and pre-irrigation
substrate water content affect water and N leaching from containers. Journal of
Environmental Horticulture 12(4): 198-202.

Karam, F., R. Masaad, R. Bachour, C.Rhayem, and Y. Rouphael. 2009. Water and
radiation use efﬁciencies in drip-irrigated pepper (Capsicum annuum L.): response to full
and deﬁcit irrigation regimes. European Journal of Horticultural Science 74(2): 79-85.

Keever, G. J. and G. S. Cobb. 1985. Irrigation scheduling effects on container media and
canopy temperatures and grth of ‘Hershey Red’ azalea. Hortscience 20(5): 921-923.

Klooster, W.S., B.M. Cregg, R.T. Fernandez, and P. Nzokou. 2010. Growth and
Photosynthetic response of pot-in-pot-grown conifers to substrate and controlled-release
fertilizer. HortScience 45(1):1-7.

Knox, G. W. 1989. Water use and average growth index of ﬁve species of container
grown woody landscape plants. Journal of Environmental Horticulture 7(4): 136-139.

Kramer, P. J. 1987. The role of water stress in tree growth. Journal of Arboriculture
13(2): 33-38.

40

Larnack, W.F. and A.X. Niemiera. 1993. Application method affects water application
efﬁciency of spray stake-irrigated containers. Hortscience 28(6): 625-627.

Landis, TD. 1990. Containers and growing media. In: Landis, T.D., R.W. Tinus, S.E.
McDonald, and J .P. Barnett. The Container Tree Nursery Manual, Volume 2. Agric.
Handbk. 674. Washington, DC: US. Dept. Agric, For. Serv.: 41-85.

Levin, I. and F .C. Van Rooyen. 1977. Soil water ﬂow and distribution in horizontal and
vertical directions as inﬂuenced by intermittent water application. Soil Science 124(6):
355-365.

Levin, 1., RC. Van Rooyen, and RC. Van Rooyen. 1979. The effect of discharge rate and
intermittent water application by point source irrigation on the soil moisture distribution
pattern. Soil Science Society of America Journal 43(1): 8-16.

Linder, S., M.L. Benson, B.J. Myers, and R.J. Raison. 1987. Canopy dynamics and
growth of Pinus radiata. 1. Effects of irrigation and fertilization during a drought.
Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere 17(10):
1 157-1 165.

Loh, F.C.W., J. C. Grabosky, and N.L. Bassuk. 2002. Using the SPAD 502 meter to
assess chlorophyll and nitrogen content of benjamin ﬁg and cottonwood leaves.
Horttechnology 12(4): 682-686.

Lopez, R., J. Rodriguez-Calcerrada, and L. Gil. 2009. Physiological and morphological
response to water deﬁcit in seedlings of ﬁve provenances of Pinus canariensis: potential
to detect variation in drought-tolerance. Trees 23: 509-519.

Marenco, R.A., S.A. Antezana-Vera, H.C.S. Nascimento. 2009. Relationship between
speciﬁc leaf area, leaf thickness, leaf water content and SPAD-502 readings in six
Amazonian tree species. Photosynthetica 47(2): 184-190.

Martin, C.A., H.G. Ponder, and CH. Gilliam. 1989. Effects of irrigation rate and media
on growth of Acer rubrum L. in containers. Journal of Environmental Horticulture 7(1):
38-40.

Martinez, DE. and J .J . Guiamet. 2004. Distortion of the SPAD 502 chlorophyll meter
readings by changes in irradiance and leaf water status. Agronomic 24(1): 41-46.

Mathers, HM. 2007. Abiotic factors inﬂuencing root growth of woody nursery plants in
containers. HortTechnology 17(2): 1 51-162.

Maxwell, K. and 6N. Johnson. 2000. Chlorophyll ﬂuorescence - a practical guide.
Journal of Experimental Botany 51(345): 659-668.

41

MDA. 2010. Generally accepted agricultural and management practices for irrigation
water use. Michigan Department of Agriculture. 15 February 2010.
<http://michigan.gov/documents/MDA_Irrigation_GAAMP_1297 l 0__7.pdf>.

MDEQ. 2006. Water withdrawals for agricultural irrigation in Michigan. Michigan
Department of Environmental Quality. 1 February 2010.

< http://www.michigan.gov/documents/deq/deq-wd-wurp-
Agriculture2006_208270_7.pdf>.

Medrano, H., J .M. Escalona, J. Bota, J. Gulias, and J. Flexas. 2002. Regulation of
photosynthesis of C-3 plants in response to progressive drought: Stomatal conductance as
a reference parameter. Annals of Botany 89: 895-905.

Milla, R., P.B. Reich, U. Niinemets, and P. Castro-Diez. 2008. Environmental and
developmental controls on speciﬁc leaf area are little modiﬁed by leaf allometry.
Functional Ecology 22:565-576.

Monteith, J. L. 1964. Evaporation and environment. State and movement of water in
living organisms. Symp. Soc. Expt. Biol. 19:205-234.

Myers, B.J. 1988. Water-stress integral - a link between short-term stress and long-term
growth. Tree Physiology 4(4):315-323.

Myers, B.J. and J .J . Landsberg. 1989. Water stress and seedling grth of two eucalypt
species from contrasting habitats. Tree Physiology 5:207-218.

NASS. 2007. Nursery crops summary 2006. National Agricultural Statistics Service and
United States Department of Agriculture. 12 December 2010.
<http://www.nass.usda.gov/QuickStats/indexbysubject.j sp?Pass_group=Crops+%26+Pla
ns>.

Nigam, SN. and R. Aruna. 2008. Stability of soil plant analytical development (SPAD)
chlorophyll meter reading (SCMR) and speciﬁc leaf area (SLA) and their association
across varying soil moisture stress conditions in groundnut (Arachis hypogaea L.).
Euphytica 160:111-117.

Niu, G.H., D.S. Rodriguez, and W. Mackay. 2008. Growth and physiological responses
to drought stress in four oleander clones. Journal of the American Society for
Horticultural Science 133(2): 188-196.

Owen, J .S., S.L. Warren, T.E. Bilderback, and JP. Albano. 2008. Phosphorus rate,

leaching fraction, and substrate inﬂuence on inﬂuent quantity, efﬂuent nutrient content,
and response of a containerized woody ornamental crop. Hortscience 43 (3):906-912.

42

Penman, H.L. 1948. Natural evaporation from open water, bare soil and grass. Proc.
Royal Soc. London A. 193(1032):120-146.

Rathier, T.M. and CR. Frink 1989. Nitrate in runoff water from container grown juniper
and Alberta spruce under different irrigation and nitrogen fertilization regimes. Journal of
Environmental Horticulture 7(1):32-35.

Reich, PB. and T.M. Hinckley. 1989. Inﬂuence of pre-dawn water potential and soil-to-
leaf hydraulic conductance on maximum daily leaf diffusive conductance in two oak
species. Functional Ecology 3:719-726.

Reich, P.B., D.S. Ellsworth, and MB. Walters. 1998. Leaf structure (speciﬁc leaf area)
modulates photosynthesis—nitrogen relations: evidence from within and across species
and functional groups. Functional Ecology. 12: 948—958.

Roberts, BR. and V.M. Schnipke. 1987. The water requirements of ﬁve container-grown
Acer species. Hortscience 22(5):1161-1161.

Ruter, J.M. 1997. The practicality of pot-in-pot. Amer. Nurseryman 185(1):32-37.

Ruter, J .M. 1998. Pot-In-Pot production and cyclic irrigation inﬂuence growth and
irrigation efﬁciency of 'Okame' cherries. Journal of Environmental Horticulture 16(3):
159-162.

Schoene, G.,T. Yeager, and D. Harnan. 2006. Survey of container nursery irrigation
practices in west-central Florida: An educational opportunity. Horttechnology 16(4): 682-
685.

Schuch, UK. and D.W. Burger. 1997. Water use and crop coefﬁcients of woody
omamentals in containers. Journal of the American Society for Horticultural Science
122(5): 727-734.

Spomer, LA. 1982. The effect of container soil volume on plant-growth. Hortscience
17(4): 680-681.

Sun, Z.J., N.J. Livingston, R. D. Guy, and G. J. Ethier. 1996. Stable carbon isotopes as
indicators of increased water use efﬁciency and productivity in white spruce (Picea

glauca (Moench) Voss) seedlings. Plant, Cell and Environment 19:887-894.

Taiz, L. and E. Zeiger. Plant Physiology, 4th edn. Sunderland, MA: Sinauer Associates
Inc., 2006.

Thomthwaite, CW. 1944. Report of the committee on transpiration and evaporation,
1943-44. Trans. Amer. Geophys. Union 25: 683-693

43

Tirnmer, V.R. and G. Armstrong. 1989. Growth and nutrition of containerized Pinus
resinosa seedlings at varying moisture regimes. New Forests 3: 171-180.

Tumbull, M.H., D. Whitehead, D.T. Tissue, W.S.F Schuster, K.J. Brown, V.C. Engel,
and KL. Grifﬁn. 2002. Photosynthetic characteristics in canopies of Quercus rubra,
Quercus prinus and Acer rubrum differ in response to soil water availability. Oecologia
130:515—524.

Tyler, H.H., S.L. Warren, and TE. Bilderback. 1996a. Cyclic irrigation increases
irrigation application efﬁciency and decreases ammonium losses. Journal of
Environmental Horticulture 14(4): 194-198.

Tyler, H. H., S. L. Warren, and TE. Bilderback. 1996b. Reduced leaching fractions
improve irrigation use efﬁciency and nutrient efﬁcacy. Journal of Environmental
. Horticulture 14(4): 199-204.

Tyree, M.T. and J .S. Sperry. 1989. Vulnerability of xylem to cavitation and embolism.
Annual Review of Plant Physiology and Plant Molecular Biology 40: 19-38.

Wang, Q.B., M.J. Chen, and Y.C. Li. 2004. Nondestructive and rapid estimation of leaf
chlorophyll and nitrogen status of peace lily using a chlorophyll meter. Journal of Plant
Nutrition 27(3): 557-569.

Warren, S.L. and TE. Bilderback. 2002. Timing of low pressure irrigation affects plant
growth and water utilization efﬁciency. Journal of Environmental Horticulture 20(3):
184-188.

Warren, S.L. and TE. Bilderback. 2005. More plant per gallon: Getting more out of your
water. Horttechnology 15(1): 14-1 8.

Warsaw, A.L., R.T. Fernandez, B.M. Cregg, and J .A. Andresen. 2009a. Water
conservation, growth, and water use efﬁciency of container-grown woody omamentals
irrigated based on daily water use. Hortscience 44(5): 1308-1318.

Warsaw, A.L., R.T. Fernandez, B.M. Cregg, and J.A. Andresen. 2009b. Container-grown
ornamental plant grth and water runoff nutrient content and volume under four
irrigation treatments. Hortscience 44(6): 1573-1580.

Weatherspoon, D.M. and CC. Harrell. 1980. Evaluation of drip irrigation for container
production of woody landscape plants. Hortscience 15(4): 488-489.

Witrner, R. 2000. Water use of landscape trees during pot-in-pot production and during

establishment in the landscape. Horticulture. Blacksburg, Virginia Polytechnic Institute
and State University. Doctor of Philosophy: 195.

44

Yeager, T., T. Bilderback, D. Fare, C. Gilliam, J. Lea-Cox, A. Niemiera, J. Ruter, K. Tilt,
S. Warren, T. Whitwell, and R. Wright. 2007. Best management practices: Guide for
producing nursery crops. 2nd ed. Southern Nursery Assn., Atlanta.

Yoo, C.Y., H.E. Pence, P.M. Hasegawa, and M.V. Mickelbart. 2009. Regulation of
transpiration to improve crop water use. Critical Reviews in Plant Sciences 28: (6)410-
431.

Zhang, J. and BM Cregg. 2005. Grth and physiological responses to varied
environments among populations of Pinus ponderosa. Forest Ecology and Management
219: 1-12.

Zhu, H., C.R. Krause, R.H. Zondag, R.D. Brazee, R.C. Derksen, M.E. Reding, and NR.
Fausey. 2005. A new system to monitor water and nutrient use in pot-in-pot

nursery production systems. J. Environ. Hort. 23(1):47-53.

Zur, B. 1976. Pulsed irrigation principle for controlled soil wetting. Soil Science 122(5):
282-291.

45

CHAPTER TWO

GROWTH AND PHYSIOLOGY

OF DECIDUOUS SHADE TREES

GROWN UNDER CYCLIC IRRIGATION

46

.lbstra

prnluc
reglm:
conui
hlldu
Glut:
'hlon
nsig:
high 1
come
rate.
grim
irrig.
qcl:
equa
tab
the r
Inca:

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Abstract

Efﬁcient water management is essential for sustainable container nursery
production. The objective of this study was to quantify the effects of cyclic irrigation
regimes on the growth, water use efﬁciency (WUE), and physiology of common
container-grown deciduous shade trees in Pot-in-Pot (PIP) production in the upper
Midwest. Trees from seven taxa (Acerfreemanii ‘Jeffersred’, A. rubrum ‘F ranksred’,
Gleditsia triacanthos ‘Harve’, Gleditsia triacanthos ‘Skyline’, Quercus rubra, Ulmus
‘Morton’, and Ulmus ‘Morton Glossy’), grown in #25 containers, were randomly
assigned to irrigation regimes with varying combinations of irrigation rates (low and
high) and daily cycle frequencies (one or four). Low and high irrigation rates
corresponded to 1 cm and 2 cm depths, respectively. Applications of the low irrigation
rate, regardless of the number of cycles in which it was applied, reduced stem radial
grth of all taxa except A. freemanii and G. triacanthos ‘Harve’ compared to the high

irrigation rate. Physiological parameters were more responsive to irrigation rate than

cycle frequency. Mid-day leaf stomatal conductance (gs) of trees irrigated cyclically was

equal to or less than trees irrigated once daily. increasing cycle frequency only increased

carbon isotope discrimination (A) of foliar and wood tissue in A. rubrum trees. Overall,

the response of instantaneous water use efﬁciency (WUEi) derived from gas exchange

measurements to inigation treatment was inconsistent. A of plant tissue is a more

sensitive indicator of plant water stress compared to WUE; derived from leaf gas

exchange measurements.

47

Introduction

Water management is a growing concern for nursery producers because of a predicted
decrease in water availability, anticipated increase in water costs, and stricter water use
regulations (Beeson et al., 2004). Growers commonly overwater, applying a ﬁxed rate of
irrigation exceeding plant water use, which may result in excessive water withdrawals.
Container growing also required the addition of fertilizer for optimum crop growth. The
resulting, and often highly concentrated, container solution is highly susceptible to
leaching, due to the low cation exchange capacity of commonly used pine-bark based
substrates (Bilderback, 2001a). The development of irrigation programs which conserve
water without sacriﬁcing tree grth and quality will allow the nursery industry to
reduce input costs and adapt to future water use regulations and decreased water
availability.

Plant responses to cyclic irrigation, a method by which fractions of a plant’s daily
water allowance is applied in multiple cycles, include higher growth index, root growth,
trunk diameter, shoot dry weight, height, and crop yield than plants receiving irrigation in
only one cycle (Beeson and Haydu, 1995; Fain et al., 1999; Ismail et al., 2007; Keever
and Cobb, 1985; Ruter, 1998; Witrner, 2000). In some cases, caliper growth was 25%
greater using cyclic irrigation compared to the traditional method of applying a single
cycle in the morning (Beeson and Haydu, 1995; Fain et al., 1999; Witrner, 2000).

Equal or superior growth rates of woody ornamental crops at reduced irrigation
volumes compared to commonly applied irrigation rates have also been documented
compared to commonly applied irrigation rates (Groves et al., 1998; Martin et al., 1989;

Roberts and Schnipke, 1987; Warsaw et al., 2009a; Warsaw et al., 2009b). Beeson and

48

do

Z:

Haydu (1995) summarized that under cyclic irrigation, the water volume required per
area can be reduced by at least 25% and 50% for xeric or mesic species, respectively,
with no effect on growth compared to standard overhead irrigation. However, there may
be a trade-off between water conservation and plant productivity if irrigation volume
does not meet plant demand (Groves et al., 1998).

Up to 97% of water taken up by a plant is transpired through stomata (Taiz and
Zeiger, 2006), and the initial response to limited water availability is stomatal closure
(Hand et al., 1982; Medrano et al., 2002), which prohibits C02 uptake and reduces
assimilation (A). It has been hypothesized that cyclic irrigation increases growth by
removing or reducing mid-day water limitations, thereby increasing the cumulative time
of photosynthesis (Beeson, 1992; Witrner, 2000).

The relationship between transpiration and assimilation is the water use efﬁciency
(WUE) and can be viewed as a measure of how efﬁciently a plant is using water to
produce biomass (Anyia and Herzog, 2004). Several studies have demonstrated increases
in WUE when trees are exposed to water-lirniting irrigation regimes (Anyia and Herzog,
2004; Ningbo et al., 2009; Warren and Bilderback, 2002). There are three methods
commonly used to calculate WUE: instantaneous WUE (WUEi), integrated WUE, and
transpiration efﬁciency.

Instantaneous WUE measures WUE at the leaf level, and is the ratio of the rate of
C02 assimilation (measured at the leaf level) ratio to the rate of water transpired (E) or
the rate of C02 uptake (gs). It is calculated using gas exchange data as:

MB or A/gs

49

 

hlS’t

€11

Instantaneous WUE excludes carbon losses due to respiration and non-photosynthetic
functions and is referred to as intrinsic WUE, because the response of E to changes in gs
and VPD is inherent to a species (Bauerle et al., 2006; Bsoul et al., 2007; Cernusak et al.,
2009). Reductions in transpirational losses without concomitant reductions in A can
increase WUE; and lead to substantial long-term increases in WUE (Yoo et al., 2009).

Stable carbon isotope analysis has become an important method of assessing
environmental stress. Carbon isotope discrimination (A), using the ratio of intercellular
13C to 12C, is used to calculate integrated water use efﬁciency, so-called because it
provides a cumulative measure of plant status over the time tissues were formed. Plants
discriminate against 13C, the heavier isotope, during photosynthesis and preferentially
incorporate 12C, the lighter isotope, into biomass. As water stress increases however,
isotope discrimination decreases, increasing the 13CDC in plant tissue. Water stress and
the subsequent stomatal closure result in increased 13'C:]2C of tissue relative to non-
water-stressed plants, as intracellular 12C is depleted and 13C is used as a reactant in
photosynthesis (Cregg and Zhang, 2000).

Ecological studies have documented decreases in A of deciduous shade tree
species in response to limited water availability (Gouveia and Freitas, 2009; Keitel et al.,
2006; Merchant et al., 2010); however, these studies have only included ﬁeld-grown
trees. By deﬁnition, A of plants grown under ambient C02 concentrations is a product of

l
3C: 2C (8) ﬁxed by Rubisco (carboxylation) and can be used as a surrogate for

l
gs and
WUE; (Cregg and Zhang, 2000; Seibt et al., 2008). A is inversely related to WUE; (A/gs),
because as A increases or gs decreases, C 1 decreases, therefore increasing 6 and

decreasing A (Cregg and Zhang, 2000).

50

Transpiration efﬁciency (TB) is the relationship between water used by a plant
and the total biomass produced and represents the whole plant water use efﬁciency. This
method takes into account water used in other metabolic processes besides
photosynthesis and is calculated as

[biomass produced / water used]

Water-limiting irrigation regimes have been used to increase the TE of a number of plants
including Capsicum annuum L., Catharanthus roseus, and Olea europaea (Bacelar et al.,
2007; Jaleel et al., 2008; Karam et al., 2009). Cyclic irrigation has been used to increase
the TB of tomatoes by 15% compared to single applications (Ismail etal., 2007).

i This study is part of an overall program to improve nursery production of
potential ash tree replacement species in the upper Midwest. It was designed to test the
effects of cyclic irrigation regimes on PIP-grown deciduous shade trees in Northern
temperate climates. The main goal was to develop irrigation guidelines for growers in the
upper Midwest that conserve water and reduce leaching of nutrients without sacriﬁcing
crop growth. The objectives of this study were to 1) determine effects of cyclic irrigation
programs on tree growth, 2) explore underlying physiological mechanisms, and 3)
examine the fate of nutrients in response to cyclic irrigation treatments. We also sought to
compare various methods of WUE measurements.

Materials and Methods
Site description and experimental design

This study was conducted at the Sandhill site at the Michigan State University

Horticulture Teaching and Research Center (HTRC) (lat.: 42.6734°N, long.: 84.4870°E,

elev.: 264 m) in Holt, Michigan. Trees were grown using a pot-in-pot (PIP) system. The

51

soil (
that
Rim
1135

FIJI

Sc

fa

soil on site was a well-drained loamy sand (83.1% sand, 8.7% silt, 9.3% clay). Tree
spacing was 1.4 m and 1.8 m on-center within rows and between rows with rows offset.
Rims of the socket pots were approximately 2.5 cm above the ground, and the ground
was covered with landscape fabric to control weeds.
Plant materials
In April 2008, one-hundred-and-sixty 25 to 37 cm (1” to 1-'/2”) diameter bare-root liners
(J. Frank Schmidt and Son Co., Boring, OR) were planted in #25 (104.4 L) containers
(GL10000, Nursery Supplies, Inc., Chambersburg, PA). Sixteen trees of each taxa were
used: Acer xﬁeemanii E. Murray (rubrum x saccharinum) ‘Jeffersred’, A. rubrum L.
‘Franksred’, Gleditsia triacanthos ‘Harve’, Gleditsia triacanthos L. var. in'ermis (L.) Zab
‘Skyline’, Quercus rubra L., Ulmus. pumila L. x japonica (Rehder) Sarg. x wilsoniana
C.K. Schneid. ‘Morton Glossy’, and Ulmusjaponica (Rehder) Sarg. x wilsoniana C.K.
Schneid. ‘Morton’. Trees were planted in an 80:20 (volume:volume) mix of pine bark.
and peat moss (Renewed Earth, Inc., Kalamazoo, MI) and installed in MSU’s PIP
facility. Container capacity of the media was 44.5%.
Irrigation treatments

Four trees of each taxa were randomly assigned to one of four irrigation regimes.
Treatments consisted of combinations of daily irrigation volume and number of daily
irrigation cycles (one or four). The once-daily irrigation event occurred at 0600 h daily.
Cyclic irrigation treatments, delivering 25% of the daily water allotment in each cycle,
were applied at 0600, 1000, 1400, and 1800 hr daily. Low and high irrigation rates
corresponded to 1 cm and 2 cm depths, respectively. Low and high volumes were applied

at a rate of 9.5 L/min. and 18.9 L/min., respectively. Daily irrigation depths were based

52

on daily water use of a container-grown conifer in Michigan documented by Warsaw et
al. (2009a). Average leaching fraction, sampled from Ulmus ‘Morton Glossy’ trees on
three dates in 2009 (1 August, 6 August, and 14 August), was zero.

Irrigation was controlled by two timers (Nelson 8014 series Solo Rain); one timer
ran once daily and the other ran four times per day. Irrigation volume was controlled via
selection of emitter. During the ﬁrst half of the 2008 growing season, water was delivered
via non pressure-compensating spray stakes. Due to low distribution uniformity, the
system was retroﬁtted with pressure-compensating drip emitters (N etaﬁm, Fresno CA) in
July 2008. In July 2009, the system was retroﬁtted with PCNL pressure-compensating .
spray stakes (Netaﬁm, Fresno CA) to increase distribution uniformity within pots.

The experimental design was a strip-split plot design with number of cycles as the
main plot factor, species as the subplot factor and irrigation rate as the sub-subplot factor.
All combinations of species x irrigation rate x cycle frequency were replicated four times,
and trees were arranged in the PIP system to allow for blocking in time of physiological
measurements. One row on each side of the plot served as a guard row.

Trees were top-dressed with 400 g of 15-9-12 Osmocote® Plus 8-9 month release
(Scotts, Inc.) in the spring of 2008 and 2009. Weeds were controlled as needed through
hand-weeding. Minimal pruning was performed throughout both seasons as needed.
Growing pots were lifted from the socket pots and turned periodically throughout the
2008 season to prevent rooting out. In June 2009, air and water permeable membranes
impregnated with copper sulfate (SpinOut, Texel Agrotextiles, Quebec, Canada) were

placed between the growing pot and the socket pot to prevent rooting out. In 2008 and

53

2009 respectively, irrigation was applied from 3 June to 1 October and from 21 May to 1
October.

Growth

Tree growth was measured monthly from May to October. Growth measurements
included tree height, trunk caliper, crown spread, and light interception. Height was
measured using a standard height pole placed perpendicular to the rim on the north side
of the container. Height was measured to the highest live point of the tree. Average trunk
caliper was assessed using two measurements perpendicular to each other, north-south
and east-west, at a height 7.5 cm above the bud union. Crown spread was measured in
two directions perpendicular to each other, north-south, and east-west, to the tips of the
longest live branches, and a geometric average was calculated.

Gas exchange

Leaf gas exchange was measured periodically in each growing season using a
portable gas exchange system (LI-6400, Li-Cor, Lincoln, NE). Due to their compound
leaf structure, Gleditsia species were not included in leaf gas exchange sampling. One
fully-expanded, sun-exposed leaf on each tree was sampled using a 3x2 cm leaf chamber
equipped with a red/blue light-emitting diode light source (Li-6400-028, Li-Cor)
providing a quantum ﬂux of 1500 umol'm-zs-l. Light saturated assimilation (Amax;
umol-m-z's-l) and stomatal conductance to water vapor (gs) were measured using
optimum conditions within the chamber: C02 concentration at 400 umol°mol-] and ﬂow
of air at 500 umols’. To minimize temperature effects during sampling, the block

temperature of the Li-6400 was set at the estimated high temperature for the day.

54

Measurements were recorded after the readings had stabilized on the system’s real-time
graphics screen. Intrinsic water use efficiency (WUEi) was calculated as: Amax / gs.

Chlorophyll ﬂuorescence

The ratio of variable to maximum chlorophyll ﬂuorescence (Fv/Fm) was
measured on trees of all species (excluding Gleditsia species) using an OS-30p
chlorophyll ﬂuorometer (Opti-Sciences, Hudson, NH). On 12 August 2009, three
randomly selected, mature sun-lit leaves on each tree were harvested, and a cuvette
provided by the manufacturer was attached to the interveinal portion of each leaf. Leaves
were allowed to dark acclimate for 10 minutes before a reading was taken.

Chlorophyll content

Relative chlorophyll content was assessed using a Minolta SPAD 502 chlorophyll
meter (Spectrum Technologies Inc., Plainﬁeld, IL). The handheld device was clamped on
to a randomly selected, fully expanded leaf and the value recorded. This process was
replicated to obtain ﬁve values for each tree.

Carbon isotope discrimination

Leaves from all trees except Gleditsia species were collected on 23 September
2009 and dried to a constant weight. At the end of the 2009 season, stem tissue was
harvested 7.5 cm above the graft union using an increment corer and dried to a constant
weight. In cases where rings were not visible, cores were dyed with stain to improve ring
identiﬁcation. If rings were still not distinguishable, trees were destructively harvested
and a 1.25 cm sample of the trunk removed and sanded to improve ring identiﬁcation.
Rings were separated by year and 1-2 mg of tissue spanning the width of the ring was

removed. Foliar tissue was ground using a coffee grinder and passed through a #40

55

screen. Foliar (2-3 mg) and wood (1-2 mg) tissue was packed into 5x9 mm tin capsules
and placed in a 96-well sample tray. Samples were sent to the University of California at
Davis Stable Isotope Facility for analysis of the relative abundance of 13C and 12C. The
resulting A values were expressed relative to international standards PeeDee Belemnite
(limestone) (Craig, 1957).

Diurnal water potential

Leaf water potential (‘1’) of all trees within two taxa (Q. rubra and Acer species)
was measured on two dates during the growing season; once on a day with relatively low
VPD and once on a day with relatively high VPD. We selected Q. rubra and Acer trees
for sampling, because they have contrasting vessel arrangements and hydraulic
architecture; Quercus trees have a ring porous vessel arrangement, while Acer trees have
a diffuse porous arrangement. A.- ﬁeemani was sampled on 21 and 26 August 2008 and
13 August 2009, and A. rubrum was sampled on 22 June 2009. Times of sampling
corresponded with gas exchange measurements. At two hour intervals, from pre-dawn to
2000 hours, one fully expanded leaf per tree was measured for gas exchange then
harvested. Leaves were stored in an airtight plastic bag in a cooler of ice until the leaf
water potential (‘1’) was determined using a PMS pressure chamber (PMS, Albany, OR).
Dates of sampling were 25 June and 18 July in 2008 and 13 June and 13 August 2009.
On 13 August 2009, a standard chamber using ambient environmental conditions was
used for gas exchange measurements.

Specific leaf area and foliar analysis

All trees except Gleditsia species were sampled for speciﬁc leaf area (SLA). A

random subsample of 20 ﬁilly expanded, sun-lit leaves from each tree was harvested in

56

July 2009. Leaves were scanned with a leaf area meter (LI-3000, Li-Cor), then oven-
dried to a constant weight. Speciﬁc leaf area was calculated as: leaf weight (g) / leaf area
(g). Leaves were harvested from all species excluding Gleditsia on 27 July, 2009, dried,
and sent to a commercial lab for foliar nutrient analysis (Scotts Inc., Lincoln, NE).
Substrate moisture measurements

Sixteen trees spanning two blocks and representing each species and treatment
were monitored throughout the 2009 season for substrate moisture and temperature. One
30-cm long moisture probe (CS616, Campbell Scientiﬁc) measuring volumetric water
content (V WC) was installed in each pot approximately 10 cm from the edge of the
container at a 45° angle. Probes were connected to a CR1000 datalogger (Campbell
Scientiﬁc) and measured temperature every 30 seconds while recording 15-minute
averages. Maximum, minimum, and average temperatures along with time of maximum
and time of minimum were recorded every 1 hour. Substrate VWC values were calibrated
for organic substrates according to manufacturer’s standards. Two electrical rain gauge
transmitters (Texas Electronics, Inc., Dallas, TX) were installed to estimate precipitation
and connected to the datalogger via the multiplexer.

Nitrate-N, pH, and electrical conductivity in leachate

Leachate was collected from a subsample of three species using the pour-through
procedure (Wright et al., 1986; Bilderback, 2001b). Acerﬁ'eemani, Ulmus ‘Morton
Glossy’, and G. triacanthos ‘Skyline’ (16 of each) were sampled in July 2008 and in May
and July 2009. Growing pots were removed from socket pots, then media was saturated
and allowed to drain for 30 minutes. Four liters of water were then applied to each tree,

and leachate was collected. Electrical conductivity (EC; Oakton Con110 series, Eutech

57

Instruments, Vernon Hills, IL) and pH (AB15 Accumet basic, Fisher Scientiﬁc,
Pittsburgh, PA) were measured in the laboratory after collection. Nitrate-N analysis was
performed by the MSU Soil and Plant Nutrient Laboratory using ﬂow injection with
cadmium reduction (Huffman and Barbarick, 1981). Irrigation water, which was sampled
at each collection time, averaged: N03-N, 0.24 ppm; EC, 0.8 dS/M; and pH, 7.8.

Statistical analysis

Data were analyzed using SAS version 9.1 software (SAS Institute Inc., Cary,
NC). All variables were tested for normality using PROC UNIVARIATE. PROC
MIXED was used to conduct analyses of variance (AN OVA) for all variables. Mean
separation was performed using Tukey's adjustment. The effects of sampling time for gas
exchange, WUEi, ‘I’, SPAD readings, foliar chlorophyll content (CC), and leachate NO3-
N, pH, and EC data were analyzed using repeated measures within PROC MIXED. Mid-
day gs and leachate NO3-N was analyzed using a log transformation, and WUE; was -
analyzed using a square-root transformation. Pearson correlation coefﬁcients for grth
and physiological parameters were determined using PROC CORR.
Results

Weather

Mean maximum daily air temperatures during the growing seasons (1 May to 1
October) were 250°C and 23.8°C for 2008 and 2009, respectively. Total precipitation
amounts during that time were 462 mm in 2008 and 425 mm in 2009. Total (1 May to 1
October) reference evapotranspiration (ETo) during the growing seasons exceeded
rainfall by 308 mm and 244 mm in 2008 and 2009, respectively (Fig. 2.1). The average

minimum and maximum air temperatures during the winter months (1 December 2008 to

58

31 March 2009), as reported by the Michigan Automated Weather Network (MAWN),
were -7.9°C and 20°C (2010).

Substrate moisture

High irrigation rates applied cyclically resulted in greater increases in substrate
moisture than low rates applied cyclically. Irrigating cyclically decreased the amplitude
of daily ﬂuctuations in substrate moisture content. Within the season, substrate moisture
ﬂuctuations varied greatly (Fig. 2.2).

Water use
Daily water use was estimated from volumetric moisture content data of four species: A.
rubrum, G. triacanthos ‘Harve’, Q. rubra, and Ulmus ‘Morton’ for the 2009 growing
season. Average daily water use over the course of the growing season was highest in
Ulmus ‘Morton’, followed by A. rubrum, Q. rubra, and G. triacanthos ‘Harve’. Total
2009 seasonal water use of Ulmus ‘Morton’ was more than 75% that of G. triacanthos
‘Harve’. Crop coefﬁcients (Kc) peaked in September. On average, Kc values were
highest in Ulmus ‘Morton’, followed by A. rubrum, G. triacanthos ‘Harve’, and Q. rubra
(data not shown).
Growth responses

Caliper and height

Across species, tree growth was more responsive to irrigation rate than number of
irrigation cycles per day (Table 2.1). A strong species response was observed in most
growth and physiological responses. The high irrigation rate increased stem radial growth
relative to the low rate in all taxa except A. freemanii and G. triacanthos ‘Harve’ (Fig.

2.3) but increased (pS0.05) height growth only in Ulmus ‘Morton’ trees. The low rate

59

reduced (p30.05) crown growth in Ulmus species compared to the high rate. Most of the
reduction in growth caused by the low irrigation rate occurred in the second year of the
study (data not shown).
Gas exchange

Mid-day and diurnal Amax and gs responses were affected by sampling date and
taxa (Table 2.2), therefore samples were analyzed separately for each taxa and date.
There was no clear trend in gas exchange responses to irrigation treatment. Mean mid-
day Amax and gs values were lowest in Acer and Q. rubrum trees, and highest in Ulmus
trees (Table 2.3). Mean mid-day Amax values were correlated with total caliper growth of
A. ﬁeemanii (r=0.21, p50.05), Q. rubra (r=0.26, p50.01), and Ulmus ‘Morton’ (r=0.16,
p50.05)trees. Irrigation rate affected gas exchange in trees of all taxa on at least one
sampling date. Increasing the irrigation rate increased (p30.05) gs and Amax of Q. rubra,
A. ﬁ'eemanii, and Ulmus ‘Morton’ trees on one sampling date (data not shown).

The only effect of cycle frequency on mid-day gas exchange occurred late in the
2009 season in A. rubrum trees and Ulmus ‘Morton Glossy’ trees. In both instances, trees
receiving four cycles had lower (p_<_0.05) gs than trees receiving only one cycle (Fig. 2.4);
however, on one sampling date, Ulmus ‘Morton Glossy’ trees receiving the low rate in
one cycle had lower (pS0.05) Amax values than Ulmus ‘Morton Glossy’ trees in all other
treatments (Fig. 2.5).
Irrigation treatment did not affect diurnal gas exchange of Q. rubra trees. Diurnal courses
of gas exchange of Acer trees was affected by irrigation treatment on all days sampled,
and the response occurred mid-day (1200 hr to 1800 hr). The low irrigation rate reduced

(pS0.01) gs and Amax of A. rubrum trees at 1200 hr and 1600 hr, respectively on 26

60

August 2008 (Fig. 2.5). Amax and gs of A. ﬁeemanii trees was reduced (p30.05) at 1600
hr on one date (21 August 2008) when trees were irrigated with the low rate applied in
one cycle compared to the high rate in four cycles (Fig. 2.6). Amax values of A. freemanii
trees were reduced (p30.05) at 1400 hr on one date (26 August 2008) when trees were
irrigated with the low rate applied in four cycles compared to the high rate in four cycles.
The effect of cycle frequency was less evident than the effect of irrigation rate. Increasing
cycle frequency increased (p50.05) Amax values of A. ﬁeemanii trees on only one date
(21 August 2008) at 1400 hr.
Diurnal water potential

Diurnal ‘1’ responses to irrigation regime were more pronounced than those of gas
exchange and occurred most often in the afternoon hours. Values of ‘I’ of Acer trees were
higher throughout the day than those of Q. rubra trees in 2008 but were similar in 2009.
Acer trees were also more responsive to irrigation regime than Q. rubra trees. There was
only one date (23 June 2009) on which ‘I’ of Q. rubra trees was affected by irrigation
treatment; at 1200 hr and 1600 hr, the low irrigation rate reduced @3005) ‘I‘ compared to
trees irrigated with the high rate (Fig. 2.7). The response of ‘I’ of Acer trees to irrigation
treatment was inconsistent (Fig. 2.8). The low irrigation rate reduced (p30.05) ‘1’ values
of Acer trees in the afternoon hours (1400 hr and 1800 hr) on only one (13 August 2009)
of the four dates sampled (data not shown). Within cyclic irrigation treatments, Acer trees
receiving the high rate had lower (p50.05) ‘1’ values than Acer trees receiving the low rate
on two dates. Pre-dawn water potential values were similar regardless of irrigation
treatments.

WUE

61

Instantaneous W UE

Mid-day WUE; values calculated from mid-day gas exchange measurements were
affected by sampling date and taxa, therefore samples were analyzed separately for each
taxa and date. On average, WUE; values were higher in year one than year two (data not
shown). Mean WUE; values varied by taxa (Table 2.3). Signiﬁcant responses of WUE;
of trees to irrigation treatments were rare and inconsistent, and all occurred in the second
year of the study. Irrigation rate did not affect WUE; of any species on any date. Values
of WUE; of A. ﬁeemanii, Q. rubra, and Ulmus ‘Morton’ trees were unresponsive to
irrigation treatment.

Cycle frequency affected WUE; of only A. rubrum and Ulmus ‘Morton Glossy’
trees. Acer rubrum trees receiving the low rate applied in one cycle had higher (p30.05)
WUE; than other trees of that species receiving any other treatment on 5 June 2009.
Increasing cycle frequency increased (p50.05) WUE; of A. rubrum on one date (31 July
2009) and Ulmus ‘Morton Glossy’ trees on one date (4 September 2009).

Integrated water use eﬂiciency

Isotopic composition of wood tissue varied by species but was unaffected by year;
therefore, year one and year two samples were pooled together for further analysis. Foliar
A values were correlated with A values of 2009 wood tissue only in Q. rubra (r=0.75,
p50.0001), Ulmus ‘Morton’ (F059, p50.0001), and A. ﬁeemanii (r=0.19, pS0.05) trees.
Quercus rubra and A. rubrum trees had the lowest A values in both foliar and wood
tissue.

Irrigation rate affected the foliar isotopic composition of only Acer and Q. rubra

trees. The low rate increased A of Q. rubra (p_<_.0.01) and Ulmus ‘Morton’ (p50.05)

62

foliage compared to the high rate (Fig. 2.9). Acer rubrum trees irrigated with the low rate
in one cycle had lower (p30.05) foliage A values than all other treatments (Fig. 2.9);
however, irrigating with only one cycle increased A values of wood tissue, regardless of
the application rate (Fig. 2.10). Analysis of wood tissue yielded signiﬁcant responses to
irrigation rate only of Ulmus trees (Fig. 2.11). Foliar A was correlated with WUE; only in
Ulmus ‘Morton’ (r=-0.17, p30.05) and Ulmus ‘Morton Glossy’ (r=-0.18, p50.05). A of
wood tissue was not correlated with WUE; in any taxa. Leaf A was correlated with mid-
day leaf gs in Ulmus ‘Morton Glossy’ (r=-0.27, p50.01), A. ﬁeemanii (r=-0.21, p50.01),
and Q. rubra (r=-0.22, p30.05) trees.
Leaf structure
Speciﬁc leaf area (SLA) and total leaf area (TLA) varied by taxa. TLA of A.
rubrum and Ulmus ‘Morton Glossy’ trees were affected (p50.05) by irrigation rate
(Table 2.4); however, the effect of irrigation treatment on SLA was not signiﬁcant in any
taxa. TLA was correlated (A. ﬁeemanii: r=0.70, p50.0001; A. rubrum: r=0.64, p50.0001;
Q. rubra: r=0.90, p50.0001; Ulmus ‘Morton’: r=0.58, p30.0001; Ulmus ‘Morton Glossy’:
r=0.43, pS0.0001) with caliper growth in all of the taxa in which TLA was measured.
Irrigating in four cycles decreased (p50.05) foliar N concentration in Q. rubra and
Ulmus ‘Morton Glossy’ trees compared to one cycle, while the high irrigation rate
reduced foliar N concentrations in Ulmus ‘Morton Glossy’ trees (p50.05) and.A. rubrum
(p50.01) trees. The trend in mean foliar N content was G. triacanthos ‘Harve’ > Q. rubra
> A. ﬁeemanii > A. rubrum > G. triacanthos ‘Skyline’ > Ulmus ‘Morton’ > Ulmus

‘Morton Glossy’.

63

Absolute chlorophyll content (CC) was calculated from SPAD values according to Parry
and Bugbee (2010). CC values were not correlated with foliar N in any taxa. CC leveled
out by 2 June 2009 in A. ﬁeemanii trees. In 2008, CC content of A. ﬁeemanii, G.
triacanthos ‘Harve’, and G. triacanthos ‘Skyline’ leaves declined between 15 September
and 25 August. In the ﬁrst year of the study, CC of A. rubrum, Q. rubra and Ulmus
‘Morton’, and Ulmus ‘Morton Glossy’ trees leveled out by sample 15 June, 5 August, and
28 August, respectively. In the second year of the study, CC of all species leveled out by
18 June, except for that of Ulmus ‘Morton Glossy’ which increased between 22 July and
11 August and that of G. triacanthos ‘Skyline’ which decreased between 1 July and 22
July.
There was no trend of foliar CC in response to inigation treatment, and results
varied by sampling date. Foliar CC of G. triacanthos ‘Harve’, Ulmus ‘Morton’, and Q.
rubra trees was unaffected by irrigation treatment at all times. The low rate decreased
(p50.05) CC of A. ﬁeemanii, A. rubrum, Ulmus ‘Morton Glossy’, and G. triacanthos
‘Skyline’ leaves on one date, regardless of the number of cycles in which irrigation was
applied; however, the low rate increased CC in A. ﬁeemanii and A. rubrum leaves on one
sampling date. Effect of cycle frequency, affecting CC of trees of only two taxa, was less
apparent than irrigation rate. Increasing cycle frequency increased (p50.05) CC in only A.
rubrum and G. triacanthos ‘Skyline’ trees on one date. There was an interaction between
rate and frequency in A. rubrum trees during week of 2 June 2009; trees receiving the
high rate in four cycles had higher (p50.05) CC than trees receiving the low rate in four
cycles. The Fv/F m values from chlorophyll ﬂuorescence measurements varied by

species, but there was no effect of irrigation treatment (data not shown).

64

Leachate
Effects of irrigation treatments on pour-through N concentration, pH, and EC varied by
date of sampling. On 1 May 2009, the high irrigation rate reduced pour-through EC
values and raised pH values compared to leachate from trees receiving the low rate.
Leachate NO3-N and EC levels from trees receiving water in four cycles was less than
that from leachate collected from trees receiving the same volume but delivered in one
irrigation cycle only on one date (23 July 2009). Leachate collected from pour-throughs
on this day from trees receiving the low rate in four cycles had EC values 50% less than
samples from trees receiving the same volume but delivered in one cycle.
Discussion
This study was designed to test the effects of cyclic irrigation regimes on PIP-grown
deciduous shade trees in Northern temperate climates. The overall goal was to develop
scientiﬁcally based, water-conserving irrigation guidelines for growers in the upper
Midwest. Speciﬁc objectives of this study were to 1) determine the effect of cyclic
irrigation on the growth of deciduous shade trees, 2) explore the physiological responses
which govern these growth responses, 3) examine the fate of nutrients in cyclic irrigation
programs, and 4) compare various methods of calculating water use efﬁciency.
Growth responses
We did not observe the often cited increases in growth of container-grown plants in
response to cyclic inigation (Beeson and Haydu, 1995; Fain et al., 1999; Ismail et al.,
2007; Keever and Cobb, 1985; Witrner, 2000). Most of these studies have been
conducted in warmer climates with longer growing seasons where crops are subjected to

harsher environmental conditions for prolonged periods of time. However, the 2009

65

growing season was unusually cool and wet; therefore it is possible that the stresses
which cyclic irrigation would typically alleviate occurred less often or, when they did
occur, were not as extreme as under typical conditions.
The taxa-speciﬁc differences in growth response to irrigation treatment indicate that
variations in degrees of drought stress tolerance exist among taxa. Previous studies
speculate that larger, rapidly growing taxa are more responsive to cyclic irrigation than
smaller, slow-growing types (Beeson and Haydu, 1995; Witrner, 2000). However, growth
of G. triacanthos ‘Harve’ and Ulmus ‘Morton Glossy’, the two fastest growing taxa
(based on height growth) in our study, was unresponsive to irrigation cycle frequency.
We expected that responses in the second year of the study would be more
reﬂective of treatments, compared to the ﬁrst year, when trees were likely recovering
ﬁ'om transplant stress. The enhanced grth response to irrigation rate in the second year
of the study relative to the ﬁrst year of the study could be a result of a larger tree root
mass which is more responsive to soil moisture additions than less extensive root system
(Beeson and Haydu, 1995; Witrner, 2000). Also in the second year of the study, trees
were bigger, and as such had more transpirational area resulting in greater water demand.
Growth parameters varied in their sensitivity to irrigation regime. Stern radial
growth was more responsive to irrigation treatment than height growth, as was expected.
Height growth is completed relatively early in the season, while stem radial growth
continues throughout the growing season. Therefore, stern radial growth is affected by

season-long stresses of high temperature and VPD and reduced water availability.

66

Gas exchange

Past studies have documented higher mid-day gs as a result of afternoon irrigation
compared to once-daily morning applications (Beeson, 1992); however, we observed the
opposite. A possible explanation for the reductions in mid-day gs due to the cyclic
irrigation could be due to the high VPD on the day of sampling which prevented the
water applied at 1400 hr from penetrating the substrate proﬁle. This was evident in
diurnal substrate moisture plots.

Beeson (1992) attributed increases in plant growth to cumulative reductions in
mid-day gs due to cyclic irrigation. It is possible that the relatively cool and wet
conditions of 2009 were not sufﬁcient to limit mid-day gs. Therefore, it is likely that the
reason for the consistent growth across cycle frequencies was due to maintenance of gS
during the mid-day hours.

WUE

The sporadic response of mid-day WUE; as a result of irrigation regime proves
the parameter’s limitations as an indicator of plant WUE. Because it is only a snapshot of
plant ﬁrnction at one point in time, WUE; does not accurately describe plant stress

response. We found A to be a more sensitive indicator of plant stress than WUEi, because
it incorporates the accumulated isotopic differences over the entire course of tissue
formation. Furthermore, because leaf synthesis is completed relatively early in the
growing season, we expected the isotopic composition of wood tissue to be more
sensitive to environmental stress during the growing season than that of foliar tissue. We
observed similar or stronger responses in wood tissue compared to foliar tissue of the ﬁve

taxa in which both of these carbon pools were sampled.

67

The lack of response of WUE; to irrigation regime in the ﬁrst year of the study
could be due to the relatively small number of sampling events compared to the second
year of the study. Container-grown Q. rubra trees in our study did not increase WUE;
under water-limited conditions, contrary to What has been reported in previous studies of
mature forest trees (Tumbull et al., 2002).

Given similar atmospheric 6, differences in carbon isotopic composition of plant tissue is
a function of stomatal aperture and 8 carboxylation. Therefore, reductions in foliar A of
Q. rubra and Ulmus ‘Morton’ trees indicate that the low irrigation rate was sufﬁcient to
decrease gs or 5 carboxylation during leaf synthesis and expansion. Reduced irrigation
rates induced water stress in Ulmus trees during the growing season, evidenced by the
decline of A values in Ulmus wood at reduced irrigation rates.

Carbon pools differ in their isotopic compositions (Bowling et al., 2008). In all
taxa except Acer species, we observed the well-documented 6 enrichment of wood tissue
relative to bulk leaf matter, indicating postphotosynthetic carbon isotope fractionation
(Damesin and Lelarge, 2003; Helle and Schleser, 2004; Brandes et al., 2006).
Correlations of WUE; and A have been recorded for a number of species (Roussel et al.
2009); however, we were able to correlate these parameters only in Ulmus trees,
indicating the tight linkage between g8 and A in this species.

Leaf structure
Differences in late season patterns of CC values between years one and two could be due
to variation in environmental conditions. In 2008, trees could have been responding to

water and temperature stress by breaking down chlorophyll which was apparent in CC

68

results. Mid-season declines in CC values of G. triacanthos trees could be associated
with locust mites which were present on the trees at the beginning of the season in 2009.
Studies have found that reduced leaching fractions due to cyclic irrigation regimes
improves nutrient efficacy, thereby increasing foliar N concentrations compared to once
daily applications (Allen et al., 2005; Karam et al., 1994; Tyler et al., 1996); however, we
observed the opposite. Although the reason for this is still unclear, it is possible that, on
days with high VPD, water applied during the 1400 hr cycle was not penetrating the
substrate surface. Because controlled release fertilizers are dependent on water for
nutrient release and movement of nutrients into roots is primarily a passive process,
nutrients were not available for plant uptake. Similar declines in foliar nutrient (N, P, K,
Ca, Mg) concentrations due to increasing plant moisture stress have been documented
(Tirnmer and Armstrong, 1989; Tumbull et al., 2002).

The reductions in leachate NO3-N concentration due to cyclic irrigation compared
to once daily applications concur with existing research (Fain et al., 1999; Fare et al.,
1996). It is impossible to know whether cyclic irrigation regimes tested in our study
resulted in less cumulative NO3-N leached from containers, because leaching fraction
was not measured after each irrigation event.

Electrical conductivity levels exceeded the recommended limit of 0.5 dS/M for
controlled release fertilizers. Leachate NO3-N concentration also exceeded the
recommended 15 to 25 ppm (SNA, 2007) for all treatments on all sampling dates.
Conclusion

Cyclic irrigation did not affect growth of any of the species tested; however the

reduced irrigation rate decreased growth in ﬁve of the seven taxa tested. It is likely that

69

the beneﬁcial effects of cyclic irrigation were underestimated, due to the mild summer of
2009. Growers should be more concerned with supplying a sufﬁcient irrigation rate than
the number of cycles in which it is delivered. Although the low rate reduces daily water
applications and reduces input costs, it prolongs production time, ultimately reducing
grower proﬁtability. Modest reductions of less than 50% of the 2 cm rate, which is
typical application, may not be detrimental to tree growth and should be explored in the
future. WUE; calculated from gas exchange measurements is limited in its accuracy as an

indicator of plant water stress. A of plant tissue proved to be a sensitive indicator of plant

water StI'CSS.

7O

Table 2.1: Summary analysis of variance (AN OVA) for caliper and height growth of
seven taxa of deciduous shade trees grown in #25 containers in a PIP production system

under varying combinations of irrigation rate and cycle frequencies.

 

Source of

variation d.f. Caliper Height
Spp 6 43.95*** 2406*"
Cycles 1 7.77 0.72
Spp*Cycles 6 1.27 1.16
Rate 1 64.31*** 12.50**
Spp*Rate 6 2.1 l 1.4
Cycles*Rate l 0.2 1 .24
Spp*Cycles*Rate 6 0.58 0.87

71

Table 2.2: Summary repeated measures analysis of variance (ANOVA) for mid-day

photosynthesis (Amax), leaf stomatal conductance (gs), and WUE; (Amax/gs) of A.
ﬂeemanii, A. rubrum, Q. rubra, Ulmus ‘Morton’, and Ulmus ‘Morton Glossy’ grown in
#25 containers in a PIP production system under varying combinations of irrigation rate
and cycle frequencies.

 

 

F-values
Source of Variation d.f. Amax gs WUEi
Between subjects
Species (Spp) 4 15.04*** 12.25** 4.57**
Cycles 1 2.64 0.53 0.17
Spp*Cycles 4 1.31 2.49 1.33
Rate 1 7.03* 10.69 0.47
Spp*Rate 4 0.65 0.62 0.12
Cycles*Rate 1 1.36 1.14 1.05
Spp*Cycles*Rate 4 0.29 0.25 0.60
Within subjects
Date 4 6568*" 95.68*** 20.10***
Date*Spp 16 3.19*** 3.57*** 3.09“
Date*Cycles 4 3.5M 8.09 2.91 *
Date*Rate 4 2.33 1.72 0.20
Date*Spp*Rate 16 0.74 0.77 0.99
Date" Spp*Cycles 16 0.67 0.96 1.12
Date*Cycles*Rate 4 1.85 1.62 0.39
Date*Spp*Cycles*Rate 16 0.65 0.54 0.43

 

* pS0.05; ** psom; *** psoooor

72

- -1
Table 2.3: Mean mid-day net photosynthesis (Amax§ umol-m 2-s ), leaf stomatal

conductance (gs; mol HzO-m-Z-SJ), and intrinsic water use efﬁciency (WUEi; Amax/gs)
(iSE) of ﬁve taxa of deciduous shade trees grown in #25 containers in a PIP facility
under varying combinations of irrigation rate (low, 1 cm or high, 2 cm) and daily cycle
frequencies (one or four). Means with different letters are statistically different at p50.05.
Data averaged across all sampling dates and irrigation treatments.

 

Taxa gs . Amax ’ WUEi

A. ﬁeemanii 0.065i0.004a 6.780:t0.38a 122.07i6.76a
A. rubrum 0.096i0.007ab 8.14d:0.43ab 96.7l:t3.05bc
Q. rubra 0.069i0.004a 6.70i0.35bc , 112.85zt6.44ab
Ulmus 'Morton' 0.1 13i0.007bc 9.40i0.49cd 89.60:l:2.79c
Ulmus 'Morton Glossy’ 0.142dz0.009c 10.90:l:0.50d 87.3 8:1:2. 1 5c

73

Table 2.4: Speciﬁc leaf area (SLA), total leaf area (TLA), foliar N concentration, and
chlorophyll content (CC) of seven taxa of deciduous shade trees grown in #25 containers
under two irrigation rates (low, 1 cm or high, 2 cm) on 27 July 2009. Within columns,
means with different letters are different at ps0.05. Data averaged across all cycle

 

frequencies.
SLA2 TLZA Foliar N CC
Taxa Rate (2;! cm ) (m ) (%) (mol/ m )
A. ﬁeemanii Low 133.19 4.04 3.45 26.78
High 128.23 5.07 3.33 24.67
Overall 130.88A 4.52B 3.39BC 25.73C
A. rubrum Low 121.91 6.03a 3.45b 42.52
High 125.43 9.16b 3.18a 43.25
Overall 123.67A 7.59A 3.32BC 42.88B
G. triacanthos
" Harve’ Low ---- ---- 3.97 44.29
High ---- ---- 3.83 46.71
Overall ---- ---- 3 .90A 45.42B
Q. rubra Low 129.29 5.65 3.55 26.35
High 128.64 7.46 3.51 26.22
Overall 128.99A 6.50A 3.53BA 26.29C
G. triacanthos
'Skyline’ Low ---- ---- 3 .26 24.07
High ---- ---- 3.19 22.95
Overall ---- ---- 3 .23BC 23 .5 1 C
Ulmus ‘Morton’ Low 117.04 6.15 3.19 56.06
High 113.64 8.19 3.05 52.20
Overall 1 15.34A 7.17A 3.12DC 54.13A
Ulmus 'Morton
Glossy' Low 96.37 5.58a 3 .02b 46.31
High 102.37 7.72b 2.84a 47.61
Overall 99.37B 6.65A 2.93D 46.96BA

Figure 2.1: Weekly rainfall and reference evapotranspiration (ETo) from Michigan

Automated Weather Network at Michigan State University (MSU) Hancock Turfgrass
Research Center (2008) and MSU Horticulture Teaching and Research Center, East

Lansing, MI. Rainfall deﬁcit = ETO — rainfall.

 

160
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75

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Figure 2.4: 2009 mid-day leaf stomatal conductance (gs; mol HzO'm-2'54) of ﬁve taxa

of deciduous shade trees grown in #25 containers in a PIP production system under two
irrigation rates (low, 1 cm or high, 2 cm). Data averaged across both irrigation rates
(n=40).

 

 

 

 

 

 

 

 

 

 

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78

Figure 2.5: 2009 mid-day net ﬁhotosynthetic rate (Amaxi pmol'm-z's 1), leaf stomatal
conductance (gs; mol HzO'm -s ), and instantaneous water use efﬁciency (WUEi;
Amax/gs) of ﬁve taxa of deciduous shade trees grown in #25 containers in a PIP
production system under two irrigation rates (low, 1 cm or high, 2 cm). Effect of cycle
frequency and irrigation rate was not signiﬁcant. Data averaged across both cycle
frequencies (n=40).

14

 

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Figure 2.6: Diurnal courses of stomatal conductance (gs; mol H20-m-2-s-l) of Acer

freemanii and Acer rubrum trees grown in #25 containers in a PIP production system in
2008 and 2009 under varying combinations of irrigation rate (low, 1 cm or high, 2 cm)
and cycle frequency (one or four). Data averaged across inigation rate and cycle
frequency when effect of treatment was not signiﬁcant (n=l6). Means with different
letters are signiﬁcantly different at pS0.0S.

 

 
  
      
    

 

    

 

 

 

 

    

 

 

 

 

 

 

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(I)
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l
g I
N 0.10 —
I a
E
V T .
s i E T
0.05 - _L
0.00 . . l ]

 

 

 

 

 

 

 

 

 

 

I I T

1200 1400 1600 1800 2000
Time (hr)

80

Figure 2.7: Diurnal course of leaf water potential (MPa) of Quercus rubra trees grown in
#25 containers in a PIP production system in 2008 and 2009 under varying combinations
of irrigation rate (low, 1 cm or high, 2 cm) and cycle frequency (one or four). Effect of
cycles was not signiﬁcant at any time. Data averaged across irrigation rate and cycle
frequency when effect of treatment was not signiﬁcant (n=1 6). Times when irrigation rate
was signiﬁcant, data averaged across both irrigation cycle frequencies (n=8; * pS0.05; **

psom; *** pS0.000l).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time (hr)
600 800 1000 1200 1400 1600 1800 2000
-0.02 d I
a -0.04 - 11‘—
CL
é
- -0.06 -
g T j
.9 i ii T ‘3:—
8 -0.08 a I _[_
E
(U
3 -0.10 - JTT *
-O.12 ~ L
- ow
23 June 2009 [:3 High
-0.14

81

Figure 2.8: Diurnal course of leaf water potential (MPa) of Acer ﬁeemanii trees grown in
#25 containers in a PIP production system in 2008 and 2009 under varying combinations
of irrigation rate (low, 1 cm or high, 2 cm) and cycle frequency (one or four). Effect of
cycles was not signiﬁcant. Data averaged across irrigation rate and cycle frequency when
effect of treatment was not signiﬁcant (n=1 6). Times when irrigation rate was signiﬁcant,
data averaged across both irrigation cycle frequencies (n=8; * pS0.05; ** p50.01).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time (hr)
600 800 1000 1200 1400 1600 1800 2000
l
-0.02 ~
’0.04 " J_ I
76
0.
g -0.06 ~
0 * T
f, -0.08 . l
8
E -0.10 . I j
(0
3 -012- i i if
-o_14 - - - Low
21 August 2008 :3 High
-0.02 . l i
'0.04 ‘ "rr
’8
a
g -0.06 - E
g
f, -0.08 - I 1 1'—
o .l.
Q.
g -0.10 -
m
3 -0.12 — f
-014 . - Low
26 August 2008 C: High

 

 

 

82

Figure 2.9: A values (%o) (iSE) of 2009 foliar tissue of ﬁve deciduous shade tree species
grown in #25 containers in a PIP production system under varying combinations of
irrigation rate (low, 1 cm or high, 2 cm) and daily cycle frequencies (one or four) (n=8; *
pS0.0S; ** p50.01). Effect of cycles was not signiﬁcant in any taxa except A. rubrum, in
those taxa data is averaged across cycle frequencies. In graph of A. rubrum, means with
different letters are statistically different at p50.05.

 

30

A. freemanii — LOW A. rubrum
29 - [:I High

280

A (%o)

27‘

26* -

Q. rubra Ulmus 'Morton'

 

H

 

 

 

 

 

 

 

 

 

29+

28- *

 

**

A (%o)
H

27-

 

l——-l

26-

 

 

 

 

 

 

 

_—

Ulmus 'Morton Glossy'

 

29-

280

 

H

A (%o)

27*

26-

 

 

 

 

 

 

25J

83

Figure 2.10: A values (%o) (:tSE) of 2008 and 2009 wood of Acer rubrum trees grown in
#25 containers in a PIP production system under varying combinations of irrigation rate
(low, 1 cm or high, 2 cm) and daily cycle frequencies (one or four) (n=16; ** pS0.01).
Effect of irrigation rate was not signiﬁcant; data averaged across rates.

 

 

 

 

 

 

 

 

 

 

A. rubrum
27 ‘ T **
A l
33 26 -
v T
.L
<1 25 -
24 -
23 . .
1 4

Cycle frequency

84

Figure 2.11: A values (960) (:tSE) of 2008 and 2009 wood of six deciduous shade tree
species grown in #25 containers in a PIP production system under varying combinations
of irrigation rate (low, 1 cm or high, 2 cm) and daily cycle frequencies (one or four)
(n=16; * p50.05; ** p50.01). Effect of cycle frequency was not signiﬁcant.

 

28

A. freemanii _ LOW Gleditsia 'Harve'
27 - 1:] High

26-

A (%o)

25-

24 ~___-

Gleditsia 'Skyline' Q. rubra

 

l--|

 

m

 

 

 

 

 

 

 

27‘

 

26‘

i——l

A (%o)

25-

 

F—l

24-

 

 

   

 

 

 

 

UImus 'Morton' Ulmus 'Morton Glossy'

27‘ *

 

26 . *‘k I

 

A (%o)
H

25*

244

 

 

 

 

 

 

 

 

 

 

 

23-

85

LITERATURE CITED

Allen, C. B., R. E. Will, and MA. Jacobson. 2005. Production efﬁciency and radiation
use efﬁciency of four tree species receiving irrigation and fertilization. Forest Science
51(6): 556-569.

Anyia, AD. and H. Herzog. 2004. Water use efﬁciency, leaf area, and leaf gas exchange
of cowpeas under mid-season drought. Europ. J. Agronomy 20:327-339.

Bacelar, E.A., Moutinho-Pereira, J .M., Goncalves, B.C., F erreira, HF, and CM.
Correia. 2007. Changes in growth, gas exchange, xylem hydraulic properties and water
use efficiency of three olive cultivars under contrasting water availability regimes.
Environmental and Experimental Botany 60: 1 83—192.

Beeson, Jr., R.C. 1992. Restricting overhead irrigation to dawn limits growth in
container-grown woody omamentals. Hortscience 27(9): 996-999.

Beeson, Jr., R. C. and J. Haydu. 1995. Cyclic microirrigation in container-grown
landscape plants improves plant grth and water conservation. Journal of
Environmental Horticulture 13(1): 6-1 1.

Beeson, Jr., R. C., M. A. Arnold, T.E. Bilderback, B. Bolusky, S. Chandler, H.M.
Gramling, J .D. Lea-Cox, J. R. Harris P.J. Klinger, H.M. Mathers, J .M. Ruter, and TH.
Yeager. 2004. Strategic vision of container nursery irrigation in the next ten years.
Journal of Environmental Horticulture 22(2): 113-115.

Bilderback, T.E. 2001a. Environmentally compatible container plant production
practices. Proc. Int. Symp. on Growing Media & Hydroponics. Acta Hort. 548.
International Society of Horticultural Science.

Bilderback, T.E. 2001b. Using the Pour Thru procedure for checking EC and pH for
nursery crops. NC State University Horticulture Information Leaﬂet 450.

Bowling, D.R. D.E. Pataki, and J .T. Randerson. 2008. Carbon isotopes in terrestrial
ecosystem pools and C02 ﬂuxes. New Phytologist 178:24-40.

Brandes, E., N. Kodama, K. Whittaker, C. Weston, H. Rennenberg, C. Keitel, M.A.
Adams, and A. Gessler. 2006. Short-term variation in the isotopic composition of organic
matter allocated from the leaves to the stem of Pinus sylvestris: effects of photosynthetic
and postphotosynthetic carbon isotope fractionation. Global Change Biology 1221922-
1939.

Bsoul, E., R. St Hilaire, and D.M. VanLeeuwen. 2007. Bigtooth maples from selected
provenances effectively endure deﬁcit irrigation. Hortscience 42(5): 1167-1173.

86

Cernusak, L. A., K. Winter, and BL. Turner. 2009. Physiological and isotopic (deltal 3C
and delta180) responses of three tropical tree species to water and nutrient availability.
Plant, Cell and Environment 32(10): 1441-1455. -

Cregg, B. and J. Zhang. 2000. Carbon isotope discrimination as a tool to screen for
improved drought tolerance. Proceedings of the 11th Metropolitan Tree Improvement
Alliance (METRIA) Conference, Gresham, OR.

Damesin, C. and C. Lelarge. 2003. Carbon isotope composition of current-year shoots
from Fagus sylvatica in relation to growth, respiration and use of reserves. Plant, Cell
and Environment 26(2):207-219.

Fain, G. B., K.M. Tilt, C.H. Gilliam, H.G. Ponder, and J .L. Sibley. 1999. Cyclic
irrigation improves irrigation application efﬁciency and grth of sawtooth oak. Journal
of Arboriculture 25(4): 200-203.

Fare, D. C., CH. Gilliam, G.J. Keever, and RB. Reed. 1996. Cyclic irrigation and media
affect container leachate and ageratum growth. Journal of Environmental Horticulture
14(1): 17-21.

Gouveia, A.C. and H. Freitas. 2009. Modulation of leaf attributes and water use
efﬁciency in Quercus suber along a rainfall gradient. Trees 23:267—275.

Groves, K. M., S. L. Warren, and TE. Bilderback. 1998. Irrigation volume, application,
and controlled-release fertilizers: I. Effect on plant grth and mineral nutrient content in
containerized plant production. Journal of Environmental Horticulture 16(3): 176-181.

Hand, M. J ., E. Young, and A.C. Vanconcelos. 1982. Leaf water potential, stomatal
resistance, and photosynthetic response to water stress in peach seedlings. Plant
Physiology 69: 1051-1054.

Helle, G. and G.H. Schleser, 2004. Beyond C02-ﬁxation by Rubisco — an interpretation
of l3C/12C variations in tree rings from novel intra-seasonal studies on broad-leaf trees.
Plant, Cell, and Environment 27, 367-3 80.

Huffman, SA. and K.A. Barbarick. 1981. Communications in soil science and plant
analysis. 12(1):79-89.

Ismail, S.M., K. Ozawa, and N.A. Khondaker. 2007. Inﬂuence of single and multiple
water application timings on yield and water use efﬁciency in tomato (var. First Power).
Agricultural Water Management 95(2008): 116-122.

Jaleel, C.A., R. Gopi, B. Sankar, M. Gomathinayagam, and R. Panneerselvam. 2008.
Differential responses in water use efﬁciency in two varieties of Catharanthus roseus
under drought stress. Comptes Rendus Biologies 331(1): 42-47.

87

Karam, F., R. Masaad, R. Bachour, C.Rhayem, and Y. Rouphael. 2009. Water and
radiation use efﬁciencies in drip-irrigated pepper (Capsicum annuum L.): response to full
and deﬁcit irrigation regimes. European Journal of Horticultural Science 74(2): 79—85.

Keever, G. J. and G. S. Cobb. 1985. Irrigation scheduling effects on container media and
canopy temperatures and grth of ‘Hershey Red’ azalea. Hortscience 20(5): 921-923.

Keitel,C., A. Matzarakis, H. Rennenberg, and A. Gessler. 2006. Carbon isotopic
composition and oxygen isotopic enrichment in phloem and total leaf organic matter of
European beech (F agus sylvatica L.) along a climate gradient. Plant, Cell and
Environment 29: 1492—1 507.

Martin, C.A., H.G. Ponder, and CH. Gilliam. 1989. Effects of irrigation rate and media
on growth of Acer rubrum L. in containers. Journal of Environmental Horticulture 7(1):
38-40.

Medrano, H., J .M. Escalona, J. Bota, J. Gulias, and J. Flexas. 2002. Regulation of
photosynthesis of 03 plants in response to progressive drought: Stomatal conductance as
a reference parameter. Annals of Botany 89: 895-905.

Merchant, A., A.D. Peuke, C. Keitel, C. Macfarlane, C.R. Warren, and MA. Adams.

1
2010. Phloem sap and leaf 5 3C, carbohydrates, and amino acid concentrations in
Eucalyptus globulus change systematically according to ﬂooding and water deﬁcit
treatment. Journal of Experimental Botany 61(6): 1785—1793.

Ningbo, C., T. Dub, S. Kang, F.Li, X. Hua, M. Wang, and Z. Li. 2009. Relationship
between stable carbon isotope discrimination and water use efﬁciency under regulated
deﬁcit irrigation of pear-jujube tree. Agricultural Water Management 96: 1615—1622.

Parry, C. and B. Bugbee. 2010. Leaf chlorophyll concentration: Linking relative and
absolute measurements. USDA NCERA-lOl Committee on Controlled Environment
Technology & Use, Annual Mtg. Madison, WI.

Roberts, BR. and V.M. Schnipke. 1987. The water requirements of ﬁve container-grown
Acer species. Hortscience 22(5):]161-1 161.

Roussel, M., E. Dreyer, P. Montpied, G. Le-Provost, J .M. Guehl, and O. Brendel. 2009.

. . 13 . . . . . . . . .
The diversrty of C isotope discnmrnatlon 1n a Quercus robur full-51b farmly rs

associated with differences in intrinsic water use efﬁciency, transpiration efﬁciency, and
stomatal conductance. Journal of Experimental Botany 60(8):2419-243l.

Ruter, J .M. 1998. Pot-In-Pot production and cyclic irrigation inﬂuence grth and
irrigation efﬁciency of 'Okame' cherries. Journal of Environmental Horticulture 16(3):
159-162.

88

Seibt, U., A. Rajabi, H. Grifﬁths, and J .A. Berry. 2008. Carbon isotopes and water use
efﬁciency: sense and sensitivity. Oecologia 155:441—454.

SNA. 2007. Best Management Practices Guide 2.0. Southern Nursery Association.

Taiz, L. and E. Zeiger. Plant Physiology, 4th edn. Sunderland, MA: Sinauer Associates
Inc., 2006.

Timmer, V.R. and G. Armstrong. 1989. Growth and nutrition of containerized Pinus
resinosa seedlings at varying moisture regimes. New Forests 3: 171-180.

Tumbull, M.H., D. Whitehead, D.T. Tissue, W.S.F Schuster, K.J. Brown, V.C. Engel,
and KL. Grifﬁn. 2002. Photosynthetic characteristics in canopies of Quercus rubra,

Quercus prinus and Acer rubrum differ in response to soil water availability. Oecologia
130:515—524.

Tyler, H. H., S. L. Warren, and TE. Bilderback. 1996. Reduced leaching fractions
improve irrigation use efﬁciency and nutrient efﬁcacy. Journal of Environmental
Horticulture 14(4): 199-204. -

Warren, S.L. and TE. Bilderback. 2002. Timing of low pressure irrigation affects plant
growth and water utilization efﬁciency. Journal of Environmental Horticulture 20(3):
184-188.

Warsaw, A.L., R.T. Fernandez, B.M. Cregg, and J .A. Andresen. 2009a. Water

conservation, growth, and water use efﬁciency of container-grown woody omamentals
irrigated based on daily water use. Hortscience 44(5): 1308-1318.

Warsaw, A.L., R.T. Fernandez, B.M. Cregg, and J .A. Andresen. 2009b. Container-grown
ornamental plant growth and water runoff nutrient content and volume under four
irrigation treatments. Hortscience 44(6): 1573-1580.

Witrner, R. 2000. Water use of landscape trees during pot-in-pot production and during
establishment 1n the landscape. Horticulture. Blacksburg, Virginia Polytechnic Institute
and State University. Doctor of Philosophy: 195.

Wright, RD. 1986. The pour-through nutrient extraction procedure. HortScience. 21 :227-
229.

Yoo, C.Y., H.E. Pence, P.M. Hasegawa, and M.V. Mickelbart. 2009. Regulation of

transpiration to improve crop water use. Critical Reviews in Plant Sciences 28: (6)410-
431.

89

CHAPTER THREE

GROWTH AND PHYSIOLOGY

OF CONTAINER-GROWN CONIFERS

UNDER CYCLIC IRRIGATION

90

Abstract

Cyclic irrigation, applying a plant’s daily water allowance in multiple allotments,
is effective in increasing growth in container-grown plants. The objective of this study
was to quantify the effects of cyclic irrigation regimes on the growth and physiology of
common container-grown conifer species in Pot-in—Pot (PIP) production in the upper
Midwest. Four species of conifers (Picea glauca var. densata, Picea pungens, Abies
fraseri, and Pinus strobus), grown in #3 (10.2-L) and #7 (24.5 L) containers, were
randomly assigned to irrigation regimes with varying combinations of irrigation rates
(low, medium, or high) and daily cycle frequencies (one or four). Low, medium, and high
inigation rates of trees grown in the #3 containers corresponded to 1 cm, 2 cm, and 3 cm
depths, respectively. Low and high rates of trees grown in the #7 containers corresponded
to 1 cm and 2 cm depths, respectively. Height growth of only P. strobus trees increased
under cyclic irrigation regimes, and irrigation rates did not affect height growth.

Physiological parameters were more responsive to irrigation rate than cycle frequency.

Mid-day gas exchange and instantaneous water use efﬁciency (WUEi) were unaffected

by irrigation treatment. Transpiration efﬁciency and A in foliar and wood tissue increased

at reduced irrigation rates. Increasing cycle frequency increased A in foliar and wood

tissue. Irrigation rates of 2 cm leached more NO3-N from containers and reduced foliar N

content of P. strobus and P. pungens trees grown in #7 containers compared to the 1 cm
rate. Trees of equal size can be produced with 50% less water than traditional methods,

increasing proﬁtability for growers by reducing input costs.

91

Will
dis
(B:

BXl

“ii

in:

113
lilg
yic
al.

C3

Introduction

Increased water costs, decreased water availability due to increased competition for
water resources with urban areas, and anticipation of stricter water withdrawal and
discharge regulations have caused nursery producers to rethink water use practices
(Beeson et al., 2004). Growers commonly overwater, applying a ﬁxed rate of irrigation
exceeding plant water use, which may result in excessive water withdrawals. Container
growing also required the addition of fertilizer for optimum crop growth. The resulting,
and often highly concentrated, container solution is highly susceptible to leaching, due to
the low cation exchange capacity of commonly used pine-bark based substrates
(Bilderback, 2001a). The development of irrigation programs which conserve water
without sacriﬁcing tree growth and quality will allow the nursery industry to adapt to
future water use regulations, increased input costs, and decreased water availability.

One option to conserve water is cyclic irrigation, where fractions of a plant’s daily
water allowance is applied several times daily. Plant responses to cyclic irrigation include
higher growth index, root growth, trunk diameter, shoot dry weight, height, and crop
yield than plants receiving irrigation in only one cycle (Beeson and Haydu, 1995; Fain et
al., 1999; Ismail et al., 2007; Keever and Cobb, 1985; Witrner, 2000). In some cases,
caliper growth was 25% greater using cyclic irrigation compared to the traditional
method of applying a single cycle in the morning (Beeson and Haydu, 1995; Fain et al.,
1999; Witmer, 2000).

Equal or superior growth rates of woody ornamental crops at reduced irrigation
volumes have also been documented (Beeson and Haydu, 1995; Groves et al., 1998;

Martin et al., 1989; Roberts and Schnipke, 1987; Warsaw et al., 2009a; Warsaw et al.,
92

3009

10111

spec

pro

Zei

355
01 l

311C

1hr

lor

2009b). Beeson and Haydu (1995) summarized that under cyclic irrigation the water
volume required per area can be reduced by at least 25% and 50% for xeric or mesic
species, respectively, with no effect on growth (compared to standard overhead
irrigation). However, there may be a trade-off between water conservation and plant
productivity if irrigation volume does not meet plant demand (Groves et al., 1998).

Up to 97% of water taken up by a plant is transpired through stomata (Taiz and

Zeiger, 2006), and the initial response to limited water availability is stomatal closure

(Hand et al., 1982; Medrano et al., 2002), which inhibits C02 uptake and reduces

assimilation. It has been hypothesized that cyclic irrigation increases growth by removing
or reducing mid-day water limitations, thereby delaying or preventing stomatal closure
and increasing the cumulative time of photosynthesis (Beeson, 1992; Witrner, 2000).

The relationship between transpiration and assimilation is the water use efﬁciency
(WUE) and can be viewed as a measure of how efﬁciently a plant is using water to
produce biomass (Anyia and Herzog, 2004). Several studies have demonstrated increases
in WUE when trees are exposed to water limiting inigation regimes (Anyia and Herzog,
2004; Ningbo et al., 2009; Warren and Bilderback, 2002). There are three methods
commonly used to calculate WUE: instantaneous WUE, integrated WUE, and

transpiration efficiency.

Instantaneous WUE (WUEi) measures WUE at the leaf level, and is the ratio of
the rate of C02 assimilation (measured at the leaf level) ratio to rate of water transpired

(or the rate of C02 uptake). It is calculated using gas exchange data as:

93

Inst:

phot

that

200

will

incr

prc

dis

ligl

den.

\Dr

in ll

185p

A/E or A/gs

Instantaneous WUE excludes carbon losses associated with respiration and non-

photosynthetic functions and is referred to as intrinsic WUE, because the response of E to

changes in gs and vapor pressure deﬁcit (V PD) is inherent to a species (Bauerle et al.,

2006; Bsoul et al., 2007; Cernusak et al., 2009). Reductions in transpirational losses

without concomitant reductions in A can increase WUEi and lead to substantial long-term

increases in WUE (Yoo et al., 2009).
Stable carbon isotope analysis has become an important method of assessing

environmental stress. Carbon isotope discrimination (A), using the ratio of intercellular

13 12 . . . .
C to C, rs used to calculate integrated water use efﬁcrency, so-called because 1t

provides a cumulative measure of plant status over the time tissues were formed. Plants

. . . . 13 . . . . 12
drscnmrnate agarnst C dunng photosynthesrs and preferentrally mcorporate C, the

lighter isotope, into biomass. As water stress increases however, isotope discrimination

13 . . . . 13 12 . .
decreases, and C rs more read1ly used, 1ncreasmg the C: C 1n plant tlssue. Water
. . 13 12 . .
stress and the subsequent stomatal closure result 1n 1ncreased C: C of tissue relat1ve

. 12 . 13 .
to non-water—stressed plants, as 1ntracellular C 18 depleted and C rs used as a reactant

in the photosynthesis (Cregg and Zhang, 2000).
Ecological studies have documented decreases in A of some coniferous species in

response to limited water availability (Aranda et al., 2010; Brandes et al., 2007; Olivas-
94

Gar

612

(10'

301

Elli

mﬁ

cu
dn
Tu

fun

EXp

 

Garcia et al. 2000; Zhang and Cregg, 2005). By deﬁnition, A of plants grown under

. . . 1 .
ambrent C02 concentratrons IS a product of gs and 5C 3 ﬁxed by Rubrsco
(carboxylation) and can be used as a surrogate of WUEi (Cregg and Zhang, 2000; Guehl
et al., 1995). A is inversely related to WUEi (A/gs), because as A increases or gs

. . 13 ,
decreases, Ci decreases, therefore 1ncreasrng 5 C and decreasrng A (Cregg and Zhang,

2000).

Transpiration efﬁciency (TE) is the relationship between water used by a plant
and the total biomass produced and represents the whole plant water use efﬁciency. This
method takes into account water used in other metabolic processes besides
photosynthesis and is calculated as

[biomass produced / water used]

Water-limiting irrigation regimes have been used to increase the TE of a number of plants
including Capsicum annuum L., Catharanthus roseus, and Olea europaea (Bacelar et al.,
2007; Jaleel et al., 2008; Karam et al., 2009). In a study by Ismail et al. (2007), cyclic
irrigation increased TB of tomatoes by 15% compared to single applications.

The response of WUE to drought stress is dependent on plant type, species,
cultivar, tree age, provenance, and phenotype, and can be used as a screening process for
drought resistance (Adams and Kolb, 2004; Bacelar et al., 2007; Cernusak et al., 2009;
Tumbull et al., 2002; Zhang and Cregg, 2005;). In an effort to gain insight into the
functional morphology affecting the WUE response, models have been developed, which

explain that coniferous evergreens are more resistant to drought stress (increased WUE)

95

than broadleaf trees due to sunken stomata, ligniﬁed guard cell walls, and lower pre-
dawn osmotic potential (an intrinsic measure of plant resistance to drought).

This study was designed to test the effects of cyclic irrigation regimes on PIP-
grown coniferous trees in Northern temperate climates. The overall goal was to develop
irrigation guidelines for growers in the upper Midwest that conserve water and reduce
leaching of nutrients without sacriﬁcing crop growth. The objectives of this study were to
I) determine effects of cyclic irrigation programs on tree growth, 2) explore underlying
physiological mechanisms, and 3) examine the fate of nutrients in response to cyclic
irrigation treatments. We also sought to compare various methods of WUE
measurements.

Materials and Methods
Site description and experimental design

This study was conducted at the Sandhill site of the Michigan State University
Horticulture Teaching and Research Center (HTRC) (lat.: 42.6734°N, long: 84.4870°E,
elev.: 264 m) in Holt, Michigan. This study consisted of two experiments - one using #3
(10.2 L) containers and one using #7 (24.5L) containers. Trees were grown using a pot-
in-pot (PIP) system. The soil on site was a well-drained loamy sand (83.1% sand, 8.7%
silt, 9.3% clay). Spacing of #3 and #7 containers was 0.5 m and l m on-center within
rows and between rows, respectively. Rims of the socket pots were approximately 2.5 cm
above the ground, and the ground was covered with landscape fabric to control weeds.
Plant materials

In April 2008, 400 plug+2 or 2+2 bare-root transplants (100 of four species; from

Peterson’s Riverview Nursery, LLC, Allegan, MI)'were planted in #3 containers

96

(GL1200, Nursery Supplies, Inc., Chambersburg, PA) using a 80:20 (volume: volume)
mix of pine bark and peat moss (Renewed Earth, Inc., Kalamazoo, MI). Container
capacity of the media was 44.5%. The four species used were Abiesfraseri (Pursh) Poir,
Picea pungens Engelm. var. glauca Regel, Picea glauca (Moench) Voss var. densata,
and Pinus strobus L. Also in the spring of 2008, 100 trees grown in #3 containers from a
previous study were transplanted into #7 containers (GL2800, Nursery Supplies, Inc.)
using the standard media described above.
Irrigation treatments

Daily irrigation depths were based on daily water use estimates of a container-
grown conifer in Michigan documented by Warsaw et al. (2009a). Six trees grown in #3
containers of each species were randomly assigned to one of six irrigation regimes.
Treatments imposed on trees grown in #3 containers consisted of a combination of daily
irrigation depth (1 cm, 2 cm, or 3 cm) and daily cycle frequency (one or four). For trees
grown in #3 containers, the 1-1, 2-1, and 3-1 treatments were delivered in a single
application, while the 1-4, 2-4, and 3-4 treatments were delivered in four cycles. The 1-1
and 1-4, 2-1 and 2-4, and 3-1 and 3-4 treatments received one, two, and three cm of water
daily, respectively. Four trees grown in #7 containers of each species were randomly
assigned to one of four irrigation regimes. Treatments imposed on trees grown in #7
containers consisted of a combination of daily irrigation depth (1 cm or 2 cm) and daily
cycle frequency (one or four). For trees grown in #7 containers, the 1-1 and 2-1
treatments were delivered in a single application, while the 1-4 and 2-4 treatments were
delivered in four cycles. The 1-1 and 1-4 and 2-1 and 2-4 treatments received one and

two cm of water daily, respectively.

97

Once-daily irrigation events occurred at 0600 h daily. Cyclic irrigation treatments
were applied at 0600, 1000, 1400, and 1800 h daily and applied 25% of the daily total at
each watering. Irrigation was applied from 15 May 2008 to 25 September 2008 and from
21 May to 1 October 2009.

Irrigation was controlled by two timers (Nelson 8014 series Solo Rain); one ran
once daily and the other ran four times per day, and volume was controlled via selection
of emitter. At the initiation of the studies, water was delivered via non pressure-
compensating spray stakes. In July 2008, trees in #3 containers receiving low and
medium irrigation rates and all trees in .#7 containers were retroﬁtted with pressure-
compensating drip emitters (N etaﬁm, Fresno CA) due to low distribution unifonnity
within plots. In July 2009, the #7 containers were retroﬁtted with PCNL pressure-
compensating spray stakes (N etaﬁm, Fresno CA) to increase distribution uniformity
within pots.

The experimental design was a strip-split plot design with number of cycles as the
main plot factor, species as the subplot factor and irrigation rate as the sub subplot factor.
All combinations of species x irrigation rate x cycle frequency of trees in #3 and #7
containers were replicated 12 and four times, respectively. Trees were arranged to allow
for blocking in time of physiological measurements. Both experiments were surrounded
by a row of guard trees. One row on each side of the #7 container plot served as a guard
rows, and one row on three sides and three rows on one side of the #3 container plot
served as guard rows.

Trees grown in #3 and #7 containers were top-dressed with 60 and 130 grams of

®
15-9-12 Osmocote Plus 8-9 month release (The Scotts Co., Marysville, OH),
98

respectively, in the spring of 2008 and 2009. Weeds within containers were controlled
through hand-weeding. Pots were turned periodically during the growing seasons to
prevent rooting out. In June 2009, squares of landscape fabric impregnated with copper
hydroxide (SpinOut®, SePRO, Carmel, IN) were placed between the growing pot and
socket pot in the plot of #7 containers. Minimal pruning was performed throughout both
seasons.

Growth

Tree growth (caliper and height) was measured monthly, and when possible,
measurements were taken approximately 30 days apart. At the beginning of each growing
season, prior to bud break, initial tree height was measured, with a standard meterstick,
perpendicularly from the rim on the north side of the container to the highest live point of
the tree. Average trunk caliper was assessed using a digital caliper. Two caliper
measurements were taken perpendicular to each other, north-south oriented and east-west
oriented, at a height level with the rim of the container.

Gas exchange

Picea species and A. ﬁaseri. Gas exchange was measured periodically in each
growing season using a portable gas exchange system (LI-6400, Li-Cor, Lincoln, NE)
equipped with a conifer chamber (LI-6400-05, Li-Cor). Mid-day gas exchange was
assessed on all trees in #7 containers and on four blocks (96 trees) of #3 containers
between 0900 HR and 1700 HR after shoots had fully expanded. One south-facing shoot
of the current season’s growth was selected from the upper third of the tree and ﬂagged at
the beginning of the season so that it could be used in subsequent gas exchange sampling.

If necessary, some needles were removed with scissors to ensure that the chamber was

99

adequately sealed. Light-saturated assimilation (Amax), stomatal conductance (gs), and
transpiration (B) were measured on clear days using: C02 concentration at 400

-1 . -l . . . .
umol'mol and ﬂow of arr at 500 umol-s . To m1n1mrze temperature effects dunng

each measurement run, the block temperature was set at the estimated high temperature
for the day. Measurements were recorded after the readings had stabilized on the
system’s real-time graphics screen. At the end of each season, the shoot used for gas
exchange was harvested and scanned using a leaf area meter (LI-3000, Li-Cor) to obtain
the projected shoot area, by which measurements were adjusted. Sampling dates for #3
and #7 containers were 21 July 2008 and 13 July, 6 August, 25 August, and 2 September
2009 and 22 July 2008 and 24 July, 6 August, 31 August 2009, respectively.

P. strobus. Gas exchange of P. strobus was sampled as described previously;
however, since the needles were too long to ﬁt in the conifer chamber, a 3x2 cm leaf
chamber equipped with a red/blue light-emitting diode light source (Li-6400-02B, Li-
Cor) was used to enclose a segment of needles. Two adjacent sun-lit P. strobus fascicles

(10 needles) from the upper third of the tree were held side-by-side to prevent self-

shading and clamped inside the chamber. Amax, gs, and B were measured using optimum

conditions within the chamber as described previously and a quantum ﬂux of 1500

-2 -1 . .
umol-m s . Gas exchange measurements were adjusted to reﬂect actual photosynthetic

area by harvesting a randomly selected needle for each tree and determining its radius

100

under a dissecting microscope. Total surface area was calculated assuming each needle
represented one-ﬁfth of a cylinder with a length of 3 cm (the length of the leaf chamber).

F oliar analysis

A subsarnple of sunlit needles was harvested from each tree on 27 July, 2009,
dried, and sent to a commercial lab for foliar nutrient analysis (Scotts Inc., Lincoln, NE).

Carbon isotope discrimination

All trees in #7 containers and 144 trees (six blocks) in #3 containers receiving 1-
1, 1-4, 3-1, or 3-4 treatments were sampled for carbon isotope discrimination. At the end
of the 2009 season, randomly selected branches were harvested, separated by year (2008
and 2009 growth), and dried to a constant weight. Needles were removed and ground
’with a coffee grinder. At the same time of harvest, stem tissue was sampled using pruners
or a chainsaw. A 1-cm disk of the stern was removed at a height equal to the rim of the
container (where stem diameter was measured), and 2008 and 2009 growth rings were
identiﬁed. Stem discs were clamped in a vice, sanded with ISO-grit sandpaper to aid in
distinguishing growth rings, and outer bark was removed. Rings of trees in #7 containers
were separated by year (2008 and 2009) using a hammer and chisel, and tissue was
ground with a Wiley mill (General Electric, F airﬁeld, CT). Rings of trees in #3 containers
were sampled by removing 1-2 mg of tissue spanning the width of the ring with a razor
blade. Ground foliar tissue (2-3 mg) and wood tissue (1-2 mg) was passed through a #40
sieve and packed into 5x9 mm tin capsules and placed in a 96-well sample tray. Samples

were sent to the University of California at Davis Stable Isotope Facility for analysis of

101

. l3 . .
the relat1ve abundance of C and 12C. The resultlng A values were expressed relat1ve to

international standards PeeDee Belemnite (limestone) (Craig, 195 7).

Biomass production

Total biomass was assessed by destructively harvesting a subsample of trees and
developing an allometric relationship between caliper and biomass to estimate biomass
for those trees not harvested. To develop the allometric relationship, trees within each
container size and species were grouped into four size classes based on caliper at the end
of the 2009 season. Sixteen trees from each species x size class within each plot were
destructively harvested, with the stems cut at substrate level. Tissue was dried to a
constant weight, then separated by tissue type i.e. roots, shoots, or needles. Total biomass
was determined by summing the mass of the roots, shoots, and needles. A regression
analysis was performed between the tree biomass and caliper to estimate biomass for
each tree.

Diurnal water potential

Shoot water potential (‘1’) of all A. ﬁaseri in #7 containers were measured on two
dates during each growing season — once on a day with relatively low VPD and once on a
day with relatively high VPD. At two-hour intervals, from pre-dawn to 2000 hours, one
fully expanded shoot per tree was harvested and stored in a zippered plastic bag in a
cooler of ice until ‘I’ was determined using a PMS pressure chamber (PMS, Albany, OR).
Harvested shoots were stripped of their outer bark and inserted into the pressure
Chamber’s inlet so that approximately 3 cm of the shoot was exposed. The seal was

tightened, and pressure was slowly applied until a drop of sap was visible with a

102

handlens. Times of sampling corresponded with gas exchange measurements. Dates of
sampling were 31 August and 18 September in 2008 and 16 July and 5 August in 2009.

Substrate moisture measurements

In July 2008, a substrate monitoring system was installed which monitored
sixteen trees (eight trees of two blocks) of #7 containers for substrate moisture and
temperature. One moisture probe (15 cm long) measuring volumetric water content
(VWC) was inserted in each container at a point halfway between the stem and the edge
of the container wall at a 45° angle. Probes were connected to a CR1000 datalogger via
an AM25T multiplexer (Campbell Scientiﬁc, Logan, UT), measuring VWC every 30
seconds, and recording lS-minute averages. Maximum, minimum, and average substrate
VWC along with time of maximum and time of minimum were recorded every 15
minutes and every 24 hours. Substrate VWC values were calibrated for organic substrates
according to manufacturer’s standards. Electrical rain gauge transmitters (Texas
Electronics, Inc., Dallas, TX) were installed in two empty #3 containers to estimate
precipitation and connected to the datalogger via the multiplexer.

Average leaching fraction of trees grown in #3 containers, sampled from A.
fraseri and P. strobus trees on three dates in 2009 (30 July, 31 July, and 14 August), was
11%. Leaching fraction of trees grown in #7 containers was sampled on two dates in
2009 (31 July and 14 August) and averaged zero.

Nitrate-N, pH, and electrical conductivity in leachate

Leachate was collected from a subsample of two species using the pour-through
procedure (Wright et al., 1986; Bilderback, 2001b). Abiesﬁaseri and P. strobus in four

blocks of each experiment were sampled monthly from July to September 2008 and from

103

May to July 2009. Growing pots were removed from socket pots, media was saturated,
and allowed to drain for 30 minutes. Then 0.5 L and 1.0 L of water were applied to each
tree in #3 and #7 containers, respectively; leachate was collected in 20-mL vials and
stored at 2.5C. Electrical conductivity (EC; Oakton Conl 10 series, Eutech Instruments,
Vernon Hills, IL) and pH (AB15 Accumet basic, Fisher Scientiﬁc, Pittsburgh, PA) were
measured in the laboratory after collection. Nitrate-N analysis was performed by the
MSU Soil and Plant Nutrient Laboratory using ﬂow injection with cadmium reduction
(Huffman and Barbarick, 1981). Irrigation water, which was sampled at each collection
time, averaged: N03-N, 0.24 ppm; BC, 0.8 dS/M; and pH, 7.8.

Statistical analysis

Data were analyzed using SAS version 9.1 software (SAS Institute Inc., Cary,
NC). All variables were tested for normality using PROC UNIVARIATE. PROC
MIXED was used to conduct analyses of variance (AN OVA) for all variables. Mean
separation was performed using Tukey's adjustment. The effects of sampling time for gas

exchange, ‘I’, nitrate-N, pH, and EC data were analyzed using repeated measures within

PROC MIXED. A square root transformation was used to analyze mid-day Amax of trees

grown in #3 containers, mid-day gs of trees grown in #7 containers, mid-day NO3-N

concentration of leachate collected from trees grown in #7 containers, and leachate EC

and foliar N content of trees grown in both size containers. A log transformation was

used for the analysis of mid-day WUEi, diurnal courses of gs, and biomass production of
trees grown in #3 containers. Pearson correlation coefﬁcients for stem caliper, tree

104

height, Amax, gs, canopy temperature, ‘1’, A, WUEi, and leachate NO3-N, pH, and EC

were determined using PROC CORR.
M

Weather

Mean maximum daily air temperatures during the growing seasons (1 May to 1
October) were 250°C and 23.8°C for 2008 and 2009, respectively. Total precipitation

amounts during that time were 462 mm in 2008 and 425 mm in 2009. Total seasonal (1

May to 1 October) reference evapotranspiration (ETO) exceeded rainfall by 308 mm and

244 mm in 2008 and 2009, respectively (Fig. 3.1). The average minimum and maximum
air temperatures during the winter months (1 December 2008 to 31 March 2009), as
recorded by the Michigan Automated Weather Network (MAWN), were -7.9°C and
20°C (2010).
Substrate moisture
Afternoon irrigation applications increased substrate VWC. The 2 cm depth applied
cyclically resulted in greater increases in substrate moisture than the 1 cm depth applied
cyclically. There was temporal variation in the magnitude of these ﬂuctuations. The
increases in VWC caused by 1000 hr and 1400 hr applications decreased in the beginning
of August. Within the season, substrate moisture ﬂuctuations varied greatly (Fig. 3.2).
Water use
Daily water use was estimated from volumetric moisture content data in 2009 (1 May to
1 October). Average daily water use was highest in P. strobus, followed by P. pungens,

P. glauca, and A. ﬁaseri. Total 2009 seasonal water use of P. strobus was nearly twice
105

that of Picea species. Mean crop coefﬁcients ranged from 3.4 to 5. On average, crop
coefﬁcients were highest in P. strobus, followed by A. fraseri, P. glauca, and P. pungens.

Growth

Total height and caliper growth of trees grown in #3 containers varied among
species, but was unaffected by irrigation treatment (pS0.05; Fig. 3.4). The trend in total
mean height and caliper growth during the two-year study was P. strobus > A. ﬁaseri >
P. pungens > P. glauca.

Biomass production during 2009 and ﬁnal rootzshoot ratios (R:S; needles
mass/root mass) of trees grown in #3 containers varied by species (p50.05). Irrigation
treatment did not affect biomass accumulation during the 2009 season. The average R:S
of P. pungens trees was 25% less than that of P. glauca, and the mean R:S of P. strobus
trees was more than twice that of P. pungens trees.

Height and caliper grth of trees grown in #7 containers was also species
speciﬁc. On average, A. ﬁaseri trees grown in #7 containers grew tallest, followed by P.
strobus, P. glauca, and P. pungens trees. The trend in caliper was similar (P. strobus > A.
fraseri > P. glauca > P. pungens).

Height and caliper growth of trees grown in #7 containers was greater in year two
of the study than year one. Over the two-year production cycle, irrigation regime affected
growth of only P. glauca and P. strobus trees. Picea pungens trees receiving the 2 cm
irrigation depth had greater (p50.01) caliper growth than P. pungens trees receiving the 1
cm depth (Fig. 3.3). Pinus strobus trees receiving four cycles per day had greater

(p50.05) height growth than P. strobus trees receiving only one cycle.

106

helgl
R:S
R:S

“'35

W3

bli

VE

The trend of biomass production of trees grown in #7 containers mirrored that of
height growth (A. ﬁaseri > P. strobus > P. glauca > P. pungens), and ranking of mean
R:S of trees was similar (P. strobus > A. ﬁaseri > P. glauca > P. pungens). The average
R:S of P. pungens was similar to that of P. glauca, and the mean R:S of P. strobus trees
was more than twice that of A. ﬁaseri (data not shown).

Biomass production and distribution of P. pungens trees grown in #7 containers
was affected by irrigation treatment. The 1 cm depth reduced (p 30.05) total biomass
accumulation and R:S compared to the 2 cm depth. Cycle frequency affected only
biomass accumulation of P. strobus trees as trees receiving water in four cycles had mean
values double that (p $0.05) of trees receiving water in one cycle (data not shown).
Physiological responses '

Leaf gas exchange

Due to differences in shoot morphology, gas exchange rates of the single-needle
conifers (A bies and Picea species) are presented on projected shoot area basis, while P.
strobus measurements are based on total needle area. Therefore, results for the gas
exchange parameters will be discussed separately for the two groups.

Mid-day gas exchange of single-needle conifers grown in #3 containers varied by

species, as well as date of sampling (Table 3.1). Average mid-day Amax and gs values of

Picea trees were nearly double those of A. ﬁaseri trees (Table 3.2). The high irrigation

rate increased (p30.05) Amax and gs of P. pungens and P. strobus trees grown in #3

containers compared to the low rate on one and three dates, respectively. Increasing cycle

frequency had no effect on mid-day gs and decreased (p50.05) Amax of P. glauca on one
107

date (6 August 2009). There was no effect of irrigation treatment on mid-day gas

exchange of A. fraseri trees grown in #3 containers on any date.

Mean Amax and g5 values of P. pungens trees grown in #7 containers were higher

(p £0.05) than those of A. ﬁaseri trees grown in #7 containers (Table 3.2). The response
of mid-day gas exchange of trees grown in #7 containers varied depending on sampling
date (Table 3.1). Overall, mid-day gas exchange was relatively unresponsive, except for

one date (6 August 2009) when Picea pungens trees receiving the 2-4 had higher

(p50.05) Amax and gs than trees receiving the 2-1 treatment and P. glauca trees receiving

the cyclic treatment had higher (p50.01) gs than trees receiving only one cycle. Mid-day

gas exchange of A. fraseri and P. strobus trees grown in #7 containers were unaffected by
irrigation treatment on all sampling dates.
Diurnal courses of gas exchange, ‘I’, and canopy temperature of trees grown in #7

containers were dependent on day of sampling. The signiﬁcant cycles x date and level x

date interactions in the overall ANOVAs of diurnal g5 and Amax were due to changes in

rank order of cycles and levels, respectively. On average, Amax and g5 were highest at

1000 hr and declined steadily throughout the day. Canopy temperature and ‘1’ were most

extreme at 1600 hr.

There was an effect of sampling date in the overall ANOVA of diurnal g5 and
Amax- Therefore, data were analyzed separately for each sampling date. Irrigation
treatment did not affect diurnal courses of AmaXa but inﬂuenced gs, ‘I’, and canopy

108

temperature. Although gs and ‘I’ were not affected at any single sampling time, when
pooled across all sampling times within the course of a day to obtain a mean diurnal
value, gs and ‘I’ were affected by irrigation on one date (5 August 2009) when the high
irrigation rate maintained greater (P3005) gs and ‘1’ than the low rate (Fig. 3.4; Fig. 3.5.
Both cyclic applications (p_<_0.01) and the high rate (P_<_0.05) reduced canopy temperature
throughout the day compared to the once daily application and the low rate, respectively
(data not shown).

W UE i

The AN OVA for mid-day WUE; (Amax/gs) of conifers grown in #3 containers indicated
effects of irrigation regime and date of sampling (Table 3.1). When analyzed by date,
WUEi of all tree species except A. fraseri grown in #3 containers responded to irrigation
treatment on at least one sampling date. Irrigation rate had a greater effect on WUEi than
did cycle frequency. Most often, trees irrigated with lower rates had higher WUEi values
than trees receiving a higher rate. Although P. pungens, P. glauca, and P. strobus trees
responded on at least one date, the effect of irrigation treatment averaged across all dates
was not signiﬁcant in any species (Table 3.2).

Mid-day WUE; of trees grown in #7 containers varied by species and date of
sampling, and on average was unresponsive to in'igation regime (Table 3.1). Cycle
frequency did not affect mid-day WUE; of trees grown in #7 containers, and inigation
rate affected only one species on one date (2 September 2009) when decreasing the
irrigation rate increased (P3005) mid-day WUE; of P. strobus trees. Diurnal courses of
WUEi peaked at 1400 hr, but were unresponsive to irrigation regime.

Integrated water use eﬁiciency

109

Carbon isotope discrimination values of trees grown in #3 containers varied by species
and year of tissue formation. Foliar isotopic composition of 2008 and 2009 wood and
foliage of P. glauca and P. pungens trees grown in #3 containers was similar, but differed
in A. ﬁaseri (p50.05) and P. strobus (pS0.0l) trees (wood only).

Foliar and wood A values of all species of trees grown in #3 containers, except A.
ﬁaseri, were affected by irrigation regime. The low rate decreased (p50.01)
discrimination in year two of the study in P. glauca wood and P. strobus wood and
needles compared to the high rate. Decreasing cycle frequency reduced (p50.05) A in P.
glauca wood in year one of the study and P. pungens and P. strobus wood in year two of

the study. . .
Foliar A was positively correlated (p30.05) with wood A in all species in the

second year of the study, but was positively correlated (p30.05) with A values of wood

only in A. ﬁaseri trees in the ﬁrst year of the study. Mid-day leaf gs was correlated with

foliar A values from 2008 (F039, p50.05) and 2009 (r=0.43, pS0.01) only in P. glauca
trees. A of foliar and wood tissue from 2009 was positively correlated (pS0.05) with
height and caliper growth only in P. pungens.

The isotopic composition of trees grown in #7 containers also differed by species
and age of tissue. A of wood (p50.05) and foliar tissue @3001) of P. pungens trees
grown in #7 containers were less in year two than year one. On average, discrimination in
wood tissue of P. strobus trees and in foliar tissue of P. glauca trees was less (p50.01) in
year two of the study than year one. Carbon isotopic composition of A.,ﬁaseri foliage

was similar in both years of the study when trees were grown in #7 containers.

110

The isotopic composition of trees grown in #7 containers was responsive to
irrigation regime. The reduced irrigation rate decreased (pS0.0S) discrimination in P.
pungens wood in year one, Picea glauca trees and A. ﬁaseri wood in year two, and P.
strobus foliage (p50.01) in year two of the study. The only effect of cycle frequency
occurred in P. strobus wood when trees receiving the 2-4 treatment had higher (p50.05)
A values than any other treatment (Fig. 3.6).

F oliar A values were correlated with A values of wood tissue in only P. pungens

and A. fraseri trees in years one, but were correlated in all species in year two. A of 2009

foliar tissue was correlated with mid-day Amax in all species except P. glauca. A was

correlated with tree growth in P. pungens and A . ﬁaseri trees.
TE

Water use estimates were not available for trees grown in #3 containers or all
trees grown in #7 containers due to logistical and equipment constraints; therefore TE
was only calculated for a subset of trees grown in #7 containers. TE was calculated as g
biomass produced per kg of water used; water used was determined by summing daily
water use (calculated from substrate VWC probes) from 1 May to 30 September 2009.
Pinus strobus trees were not used in TE analysis due to probe malfunction. Due to the
limited number probes measuring soil moisture, the effect of irrigation treatment on TE
could not be analyzed by species. TE was not affected by irrigation rate of cycle
frequency.

Leachate properties

111

Mean pH and EC values collected from trees grown in #3 containers was 6.5 and 1.7
dS/M, respectively. Leachate pH, EC, and N03 -N concentrations collected from trees
grown in #3 containers were affected by irrigation regime and sampling date. A
signiﬁcant rate x sampling date interaction in pH, EC, and NO3-N occurred in both years
of the study. The 2 cm irrigation rate produced leachate with the highest pH and lowest
EC in both years of the study. The 3 cm rate decreased NO3-N levels in leachate in both
years of the study.

Leachate N03 -N concentration collected from trees grown in #7 containers varied
by sampling date also. NO3 -N concentrations peaked at the beginning of the season and
then declined. NO3-N concentrations were higher (pS0.01) in leachate collected from
trees receiving the 1 cm rate compared to the 3 cm rate.

Mean leachate pH and EC values collected from trees grown in #7 containers
were 6.4 and 1.9 dS/M, respectively. Leachate pH and EC values ranged from 4.7 to 7.5
and 0.5 to 5.0 dS/M, respectively, and varied by date of sample. The only difference in
pH as a result of irrigation program was on one sampling date (23 July 2009) when trees
receiving the 2 cm rate had higher (p50.0001) mean pH values than trees receiving the 1
cm rate. BC was higher (p50.01) in leachate collected from trees receiving the 1-4
treatment compared to trees receiving the 2-4 treatment.

Plant nutrient status
The 3 cm rate reduced foliar N levels in all species grown in #3 containers compared to
the 1 cm rate (Fig. 3.7). Only P. pungens and P. strobus trees grown in #7 containers and
receiving the 2 cm rate had lower foliar N concentrations than trees receiving the 1 cm

rate (Fig. 3.8). On average, Picea species had the highest foliar N concentrations

112

regardless of the size of container in which they were grown, followed by A. fraseri and
P. strobus.
Discussion

This study was designed to test the effects of cyclic irrigation regimes on PIP-
grown coniferous trees in Northern temperate climates. The overall goal was to develop
scientiﬁcally based irrigation guidelines for growers in the upper Midwest. The
objectives of this study were to 1) determine effects of cyclic irrigation programs on the
growth of PIP-grown conifers, 2) explore underlying physiological mechanisms
governing these growth responses, and 3) examine the fate of nutrients in response to
cyclic irrigation treatments. We also sought to compare various methods of evaluating
WUE.
Growth responses

Height and caliper response

We hypothesized that cyclic irrigation would increase growth compared to once-
daily applications and that less water could be used to achieve this growth. Counter to our
hypothesis, tree height growth in three of the four species investigated was similar,
regardless of the number of cycles in which water was applied; however, we did observe
increases in height growth of one species, P. strobus, with cyclic irrigation. This growth
increase due to increasing cycle frequency is consistent with previous studies testing
cyclic irrigation on containerized woody species (Beeson, 1992; Beeson and Haydu,
1995; Fain et al., 1999; Ruter, 1998; Witrner, 2000).

Past studies testing cyclic irrigation have predominantly included broadleaf

plants, not conifers, and have been performed in the southeastern U.S., where

113

environmental conditions are much different than those in the upper Midwest. Lower
seasonal and mid-day temperatures and a shorter growing season in Northern climates
may mean that container-grown trees are subjected to less stress than similar specimens
grown in the Southwest. Therefore, increases in growth resulting from cyclic irrigation
are more subtle in the upper Midwest than in the Southwest.

Increases in tree height, the standard by which coniferous evergreen trees are sold
(AN LA, 2004), was similar regardless of irrigation rate. This is in agreement with
numerous studies which have demonstrated equal or superior grth rates of woody
ornamental crops at reduced irrigation volumes (Beeson and Haydu, 1995; Groves et al.,
1998; Martin et al., 1989; Roberts and Schnipke, 1987; Warsaw et al., 2009a; Warsaw et
al., 2009b).

Contrasting responses of growth parameters were also observed. Stem radial
growth was more responsive to irrigation treatment than height growth. Height growth is
largely determined during bud formation in the previous year and is completed relatively
early in the season whereas radial growth continues throughout the growing season.
Therefore, height growth is not subject to environmental stresses such as inadequate
water availability and supra-optimal temperatures, which are common in mid to late
summer.

Observations of larger, fast-growing container-grown plants being more
responsive to cyclic irrigation than those that are smaller and slow-growing have also
been documented (Beeson and Haydu, 1995; Witrner, 2000). Moreover, species
possessing the ability to adapt to drought stress also have an advantage in maintaining

growth under reduced water availability; however, some responses, like increased R:S

114

may be limited by the restricted media volume of containers. We hypothesized that the
growth response to cyclic irrigation would be greater in 1) relatively fast-growing trees
like P. strobus and P. pungens and 2) year two of the study than in year one.
We expected tree grth to be more reﬂective of the imposed treatments in year two of
the study than in year one; however, in 2009 Michigan experienced its sixth coolest
summer on record since 1895. More importantly, the period from June to August 2009
was the ﬁfth coolest ever recorded for this period (N OAA, 2009). Additionally, an excess
of 87 mm of precipitation fell from 15 June to 15 August 2009 compared to the same
period in 2008. The mild conditions of 2009 may have been a factor in the general
unresponsiveness to cyclic treatments in the second year of the study. In 2008, growth of
trees in #7 containers was more responsive to irrigation treatment than in 2009. During
2008, trees may also have been undergoing transplant stress from initial planting in May
of that year. Our results suggest that cyclic irrigation may be useful in reducing plant
water stress during establishment.
Physiological responses

Previous studies testing cyclic irrigation on broadleaf woody omamentals have
attributed the resulting increase in growth to cumulative reductions in mid-day water

stress (Beeson, 1992; Witrner, 2000) and subsequent prevention of stomatal closure

(greater gs), therefore increasing net photosynthesis (Beeson, 1992; Witrner, 2000).

Based on this theory, we expected that applying a pulse of irrigation in the aftemoon

would dampen the mid-day ﬂuctuations of gas exchange; however, most often we

obtained similar mid-day gs values regardless of irrigation cycle frequency. The

115

sampling date on which increasing cycle frequency increased mid-day g5 was preceded

by four days without precipitation, whereas the other sampling dates were preceded by at

most two rain-free days. This indicates that cyclic irrigation may only be effective in

maintaining mid-day gs under hotter and drier conditions than were typical in 2009.

Empirical models describing gs as a function of soil moisture availability predict

that conifers are more drought tolerant than broadleaf trees and shrubs due to their lower
osmotic potential, sunken stomata, and ligniﬁed guard cell walls (Gao et al., 2002). This
may explain the relative unresponsiveness of conifers in our study to cyclic water

applications compared to broadleaf trees and shrubs in previous studies.

The increases in mid-day Amax and gs of P. strobus trees grown in #3 containers

due to increased substrate moisture due to higher irrigation rates is similar to observations
of mature P. strobus forest trees under mesic and drought conditions (Maier and ‘Teskey,

1992). Reductions in caliper grth of P. pungens trees grown in #7 containers caused by

the decreased irrigation rate was not accompanied by reductions in mid-day Amax and

both P. pungens and P. strobus trees grown in #3 containers had lower mid-day Amax

caused by the reduced irrigation rate without concomitant reductions in growth. This

decoupling of gas exchange and grth suggests that other factors besides Amax were

limiting growth.

116

Mid-day ‘I’, a measure of plant water status, is often of interest when testing cyclic
irrigation. High ‘1' is not necessarily a result of well-watered, non-stressed trees, but can

also be caused by partially closed stomata in response to drought stress (Reich and

Hinckley, 1989); however, the concurrent higher gs and ‘1’ due to the high irrigation rate

that we observed in our study indicate that trees receiving the high irrigation rate were
less stressed than those receiving the low rate. The consistency of ‘1’ across all cycle
frequencies in our study differs from past studies testing cyclic irrigation on container-
grown broadleaf trees (Beeson, 1992; Beeson and Haydu, 1995). During the nighttime,
plant water status equilibrates with that of the substrate; as such, pre-dawn values of ‘I’
are assumed to be equivalent to those of the substrate. On two of the three days sampled,
we found differences in pre-dawn ‘1’ between plants irrigated with the high rate and those
receiving the low rate. This is similar to observations of two-year-old P. ponderosa

seedlings under water-stressed and well-watered conditions (Olivas-Garcia et al., 2000).

Furthermore, the reductions in mean diurnal ‘I’ and gs of A. ﬁaseri trees caused by the

reduced irrigation rate mimics the effects of high root-zone temperatures on A. rubrum

trees documented by Graves et al. (1989).

The effect of irrigation regimes on WUE; was highly dependent on environmental

conditions. The parameter’s inconsistent response demonstrates the method’s limitations

as an accurate predictor of WUE. Within the #3 containers, the species with the highest

WUEi (P. strobus) was most capable of handling water stress and therefore did not

experience large reductions in growth as a result of water-limiting irrigation regimes. We

117

were unable to link the growth decline of P. strobus trees in #7 containers as a result of

irrigation cycle frequency to reductions in mid-day gas exchange. Increases of WUEi

preceding 1400 hr conﬁrm the occurrence of mid-day reductions in g3 relative to Amax

(Beeson, 1992).

WUE; and A have been correlated in a number of species (Roussel et al. 2009); however,

we did not ﬁnd signiﬁcant relationships between these parameters in most of the species

tested. This might be due to the fact that WUE; represents gas exchange of sun-lit foliage

on clear days and does not take into account gas exchange of shaded foliage, the effect of
cloudy days, or plant respiration.

The increases in A that we observed in response to cycle frequency indicate that the
cyclic treatments created improved the water status in some species. F oliar N can be used
as a surrogate for carboxylation capacity (Adams and Kolb, 2004; Field and Mooney,
1986). Regardless of container size in which trees were grown, leaf and wood A values of
trees receiving the high irrigation rate were equal to or exceeded those of trees receiving
the low irrigation rate, while foliar N concentrations were similar to or were reduced by
the higher irrigation rate. These contrasting responses indicate that reduced carboxylation

capacity due to reduced foliar N at high irrigation rates was not a factor affecting A of

. . . . . . . l3 . .
trees. Thus, it was thought that gs must be lrmrtrng assrmrlatron of C Into plant trssue.
The relationship between WUEi and A is stronger than that of gs and A and Amax

and A, because the drawdown of C i is actually a function of Amaxigs- Concomitant
118

181

 

 

reductions of mean mid-day g5 and A were only observed in P. strobus year two wood

and foliage from trees grown in #3 containers at the low rate compared to the high rate.

WUEi is highly variable as it is a function of the relationship between A and gs and is

only a snapshot of plant functions at one point in time. A is a more accurate and sensitive
depiction of plant stress, because the signature is incorporated over the entire duration of
tissue formation.

Plant carbon pools differ in their isotopic compositions relative to leaves (Bowling et al.,

2008). We observed the well-documented l3)C enrichment of wood tissue relative to

bulk leaf matter, indicating postphotosynthetic carbon isotope fractionation (Brandes et
al., 2006; Damesin and Lelarge, 2003; Helle and Schleser, 2004). Similar to height
growth, needle composition is highly dependent on plant status at time of bud formation
during the previous year and growing conditions during needle expansion of the current
year. A of wood tissue is considered a more accurate representation of plant stress than
that of bulk leaf tissue, because the isotopic signal of annual rings is integrated over the

duration of the current growing season.

119

Leachate and nutrient responses

Electrical conductivity levels were within the recommended range of 0.2 and 0.5
dS/M for controlled release fertilizers (Bilderback, 2001b). Theoretically, soluble salts
will accumulate faster in containers receiving low irrigation volumes, as with the low rate
and/or cyclic regimes, than containers receiving high irrigation amounts. We observed
similar EC values regardless of irrigation cycle frequency. In #3 containers, the reduction
in soluble salts at the 3 cm rate was likely due to increased leaching of nutrients and was
conﬁrmed visually by chlorosis of P. strobus needles during the second growing season.
Substrate pH was rarely within the recommended range of 5 to 6 (Bilderback, 2001b).
This is likely a result of the alkaline water (average 7.8), typical of Michigan
groundwater, which was applied to trees.
Nitrate-N levels in leachate exceeded the recommended 15 to 25 ppm (Bilderback,
2001b) for all treatments. We did not observe the previously documented reductions in
leachate NO3-N concentrations as a result of cycle frequency (Fare et al., 1996; Tyler et
al. 1996a); however, decreased leachate NO3-N concentrations were observed in trees
receiving the high rate versus the low rate. These results are consistent with ﬁndings of
previous studies (Tyler et al., 1996b; Warsaw et al., 2009b).
The reason for the differences in early season NO3-N concentrations between years is
unclear. It is unlikely that residual nutrients from the previous year played a part,
considering the low September 2008 concentrations caused by the high irrigation rate.
Most likely, differences in temperature affected the release rate early in the season and
high precipitation increased leaching of NO3-N during the second season compared to

the ﬁrst season.

120

Plant nutrient status

An often cited beneﬁt of cyclic irrigation is increased nutrient efﬁcacy and subsequent
increases in foliar N due to reduced leaching. We found nutrient retention to be a function
of reduced irrigation rate, not increased cycle frequency. Reduced foliar N levels of P.
pungens and P. strobus trees grown in #7 containers at the 2 cm rate, representing a
typical application, indicate that growers may be leaching nutrients and sacriﬁcing

nutrient efﬁcacy using this application rate.

We did not observe the previously documented (Reich et al, 1998) increases in Amax

with rising foliar N concentrations. In fact, the only signiﬁcant correlation between Amax

and foliar N was when the two parameters were inversely related in P. strobus trees
grown in #3 containers. In this case, water limitations associated with the low irrigation

rate increased foliar N concentrations by retaining nutrients in the substrate, but restricted
Amax-

Conclusion

Cyclic irrigation increased growth only of container-grown P. strobus trees. It is
likely that the beneﬁcial effects of cyclic irrigation were underestimated, due to the mild
summer of 2009. Reducing irrigation rates by 50% is a viable method of water
conservation for container nurseries in the upper Midwest. The low irrigation rate was
enough to promote reductions in caliper growth only of P. pungens trees, regardless of
the size of container in which they were grown, suggesting that this rate may be sufﬁcient

for the other species tested. Reduced foliar N levels and increases in leachate NO3-N

121

concentration at the 2 cm rate, representing a typical application, indicate that growers
are leaching nutrients and sacriﬁcing nutrient efﬁcacy by using this application rate.
However, the decreases in grth of some species (P. pungens) at reduced irrigation
rates suggests that in some cases growers must choose between increased nutrient
retention and growth optimization. Our ﬁndings conﬁrm that carbon isotope composition

of wood tissue is a sensitive and more accurate representation of WUE than WUE].

122

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160
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Figure 3.3: Stem radial growth (:tSE) over the two-year production cycle of four
coniferous tree species grown in #7 containers in a PIP production system under varying
combinations of irrigation rate (1 or 2 cm) and daily cycle frequencies (one or four).
Effect of cycles was not signiﬁcant; data averaged across both cycle frequencies (n=8).
Means with different letters are statistically different at p50.05.

30

 

- Low
3 High ”5

25 4 b ns _}
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15

1
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Caliper growth (mm)

 

 

 

 

 

 

 

 

 

 

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Species

127

-2 -
Figure 3.4: Diurnal course of mean leaf stomatal conductance (gs; mol HZO-m 's l) and

(i813) of A. ﬁaseri trees grown in #7 containers in a PIP production system under two
irrigation rates (1, 2, or 3 cm) on three dates. Cycles x rate interactions were not
signiﬁcant, therefore data was averaged across cycles. The high inigation rate increased

(p50.05) mean diurnal gs only on 5 August 2009 (a=0.05; n=4).

 

31 August 2008

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0.0 . . . . . - . _
600 800 1000 1200 1400 1600 1800 2000

Time

128

Figure 3.5: Diurnal course of shoot water potential (MPa) (iSE) of A. ﬁaseri trees grown
in #7 containers in a PIP production system under two irrigation rates (1 or 2 cm)
(a=0.05; n=8) on three dates. Cycle frequency x level interaction was not signiﬁcant,
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water potential at pS0.05.

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Shoot water potential (MPa)

 

 

 

 

-o.14
600 800 1000 1200 1400 1600 1800 2000

Time

129

Figure 3.6: Mean (:tSE) A values of 2008 and 2009 wood of four coniferous tree species
grown in #7 containers in a PIP production system under varying combinations of
irrigation rate (1 or 2 cm) and daily cycle frequencies (1 or 4) (a=0.05; n=4).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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LITERATURE CITED

Adams, H. D. and T. E. Kolb. 2004. Drought responses of conifers in ecotone forests of
northern Arizona: tree ring grth and leaf 13C. Oecologia 140: 217-225.

ANLA. 2004. American Standard for Nursery Stock. American Nursery and Landscape
Association. ANSI Z60.1-2004. 129 pp.

Anyia, AD. and H. Herzog. 2004. Water use efﬁciency, leaf area, and leaf gas exchange
of cowpeas under mid-season drought. Europ. J. Agronomy 201327-339.

Aranda, I. R. Alia, U. Ortega, A.K. Dantas, and J. Majada. 2010. Intra-speciﬁc variability
in biomass partitioning and carbon isotopic discrimination under moderate drought stress
in seedlings from four Pinus pinaster seedlings. Tree Genetics and Genomes 6:169-178.

Bacelar, E.A., Moutinho-Pereira, J .M., Goncalves, B.C., F erreira, HR, and CM.
Correia. 2007. Changes in growth, gas exchange, xylem hydraulic properties and water
use efficiency of three olive cultivars under contrasting water availability regimes.
Environmental and Experimental Botany 60:183—192.

Bauerle, W. L., W. W. Inman, and J .B. Dudley. 2006. Leaf abscisic acid accumulation in
response to substrate water content: Linking leaf gas exchange regulation with leaf
abscisic acid concentration. Journal of the American Society for Horticultural Science
131(2): 295-301.

Beeson, Jr., R.C. 1992. Restricting overhead irrigation to dawn limits growth in
container-grown woody omamentals. Hortscience 27(9): 996-999.

Beeson, Jr., R. C. and J. Haydu. 1995. Cyclic microirrigation in container-grown
landscape plants improves plant growth and water conservation. Journal of
Environmental Horticulture 13(1): 6-1 1.

Beeson, Jr., R. C., M. A. Arnold, T.E. Bilderback, B. Bolusky, S. Chandler, H.M.
Gramling, J .D. Lea-Cox, J. R. Harris P.J. Klinger, H.M. Mathers, J .M. Ruter, and TH.
Yeager. 2004. Strategic vision of container nursery irrigation in the next ten years.
Journal of Environmental Horticulture 22(2): 113-115.

Bilderback, T.E. 2001a. Environmentally compatible container plant production
practices. Proc. Int. Symp. on Growing Media & Hydroponics. Acta Hort. 548.
International Society of Horticultural Science.

Bilderback, T.E. 2001b. Using the Pour Thru procedure for checking EC and pH for
nursery crops. NC State University Horticulture Information Leaﬂet 450.

133

Bowling, D.R. D.E. Pataki, and J .T. Randerson. 2008. Carbon isotopes in terrestrial
ecosystem pools and C02 ﬂuxes. New Phytologist 178:24-40.

Brandes, E., N. Kodama, K. Whittaker, C. Weston, H. Rennenberg, C. Keitel, M.A.
Adams, and A. Gessler. 2006. Short-term variation in the isotopic composition of organic
matter allocated from the leaves to the stem of Pinus sylvestris: effects of photosynthetic
and postphotosynthetic carbon isotope fractionation. Global Change Biology 1221922-
1939.

Brandes, E., J. Wenninger, P. Koeniger, D. Schindler, H. Rennenberg, C. Leibundgut, H.
Mayer, and A. Gessler. 2007. Assessing environmental and physiological controls over
water relations in a Scots pine (Pinus sylvestris L.)stand through analyses of stable
isotopic composition of organic matter. Plant, Cell and Environment 30:113-127.

Bsoul, E., R. St Hilaire, and D.M. VanLeeuwen. 2007. Bigtooth maples from selected
provenances effectively endure deﬁcit irrigation. Hortscience 42(5): 1167-1173.

Cernusak, L. A., K. Winter, and BL. Turner. 2009. Physiological and isotopic (delta13C
and delta] 80) responses of three tropical tree species to water and nutrient availability.
Plant, Cell and Environment 32(10): 1441-1455.

Craig, H. 1957. Isotopic standards for carbon and oxygen and correction factors for mass-
spectrometric analysis of carbon dioxide. Geochimica Et Cosmochimica Acta 12(1-2):
133-149.

Cregg, B. and J. Zhang. 2000. Carbon isotope discrimination as a tool to screen for
improved drought tolerance. Proceedings of the 11th Metropolitan Tree Improvement
Alliance (METRIA) Conference, Gresham, OR.

Damesin, C. and C. Lelarge. 2003. Carbon isotope composition of current-year shoots
from F agus sylvatica in relation to growth, respiration and use of reserves. Plant, Cell
and Environment 26(2):207-219.

Fain, G. 3., KM. Tilt, C.H. Gilliam, H.G. Ponder, and J .L. Sibley. 1999. Cyclic
inigation improves irrigation application efﬁciency and growth of sawtooth oak. Journal
of Arboriculture 25(4): 200-203.

Fare, D. C., CH. Gilliam, G.J. Keever, and RB. Reed. 1996. Cyclic irrigation and media
affect container leachate and ageratum growth. Journal of Environmental Horticulture
14(1):17-21.

Field C. and HA. Mooney. 1986. The photosynthesis-nitrogen relationship in wild
plants. In: Givnish TJ (ed) On the economy of plant form and function. Cambridge
University Press, London, p 25—55.

134

Gao, Q., P. Zhao, X. Zeng, X. Cai, and W. Shen. 2002. A model of stomatal conductance
to quantify the relationship between leaf transpiration, microclimate and soil water stress.
Plant, Cell and Environment 25: 1373-1381.

Graves, W. R., M. N. Dana, and R.J. Joly. 1989. Root-zone temperature affects water
status and growth of red maple. Journal of the American Society for Horticultural Science
114(3): 406-410.

Groves, K. M., S. L. Warren, and TE. Bilderback. 1998. Irrigation volume, application,
and controlled-release fertilizers: I. Effect on plant growth and mineral nutrient content in
containerized plant production. Journal of Environmental Horticulture 16(3): 176-181.

Guehl, J.M., C. Fort, and A. Ferhp. 1995. Differential response of leaf conductance,
carbon isotope discrimination and water use efﬁciency to nitrogen deﬁciency in
maritime pine and pedunculate oak plants. New Phytologist 131:149-157.

Hand, M. J ., E. Young, and A.C. Vanconcelos. 1982. Leaf water potential, stomatal
resistance, and photosynthetic response to water stress in peach seedlings. Plant
Physiology 69: 105 1-1054.

Haydu, J. J. and R. C. Beeson, Jr., R.C. 1997. Economic feasibility of micro-irrigating
container-grown landscape plants. Journal of Environmental Horticulture 15(1): 23-29.

Helle, G. and G.H. Schleser, 2004. Beyond C02-ﬁxation by Rubisco — an interpretation
of 13C/ 12C variations in tree rings from novel intra-seasonal studies on broad-leaf trees.
Plant, Cell, and Environment 27, 367-3 80.

Huffman, SA. and K.A. Barbarick. 1981. Communications in soil science and plant
analysis. 12(1):79-89.

Ismail, S.M., K. Ozawa, and N.A. Khondaker. 2007. Inﬂuence of single and multiple
water application timings on yield and water use efficiency in tomato (var. First Power).
Agricultural Water Management 95(2008): 116-122.

Jaleel, C.A., R. Gopi, B. Sankar, M. Gomathinayagam, and R. Panneerselvam. 2008.
Differential responses in water use efﬁciency in two varieties of Catharanthus roseus
under drought stress. Comptes Rendus Biologies 331(1): 42-47.

Karam, F., R. Masaad, R. Bachour, C.Rhayem, and Y. Rouphael. 2009. Water and
radiation use efﬁciencies in drip-irrigated pepper (Capsicum annuum L.): response to full

and deﬁcit irrigation regimes. European Journal of Horticultural Science 74(2): 79-85.

Keever, G. J. and G. S. Cobb. 1985. Irrigation scheduling effects on container media and
canopy temperatures and growth of ‘Hershey Red’ azalea. Hortscience 20(5): 921-923.

135

Maier, C.A., and RD. Teskey. 1992. Internal and external control of net photosynthesis
and stomatal conductance of mature eastern white pine (Pinus strobus). Can. J. For. Res.
22: 1387-1394.

Martin, C.A., H.G. Ponder, and OH. Gilliam. 1989. Effects of irrigation rate and media
on grth of Acer rubrum L. in containers. Journal of Environmental Horticulture 7(1):
38-40.

Medrano, H., J .M. Escalona, J. Bota, J. Gulias, and J. F lexas. 2002. Regulation of
photosynthesis of C-3 plants in response to progressive drought: Stomatal conductance as
a reference parameter. Annals of Botany 89: 895-905.

Ningbo, C., T. Dub, S. Kang, F.Li, X. Hua, M. Wang, and Z. Li. 2009. Relationship
between stable carbon isotope discrimination and water use efﬁciency under regulated
deﬁcit irrigation of pear-jujube tree. Agricultural Water Management 96: 1615-1622.

NOAA. 2009. NOAA: Summer temperature below average for US. National Oceanic
and Atmospheric Association. 10 September 2009.
<http://www.noaanews.noaa.gov/storiesZOO9/2009091 O_summerstats.html>

Olivas-Garcia, J .M., B.M. Cregg, and T.C. Hennessey. 2000. Genotypic variation in
carbon isotope discrimination and gas exchange of ponderosa pine seedlings under two
levels of water stress. Canadian Journal of Forest Research 30: 1 581-1590.

Reich, PB. and T.M. Hinckley. 1989. Inﬂuence of pre-dawn water potential and soil-to-
leaf hydraulic conductance on maximum daily leaf diffusive conductance in two oak
species. Functional Ecology 3:719-726.

Reich, P.B., D.S. Ellsworth, and MB. Walters. 1998. Leaf structure (speciﬁc leaf area)
modulates photosynthesis-nitrogen relations: evidence from within and across species
and functional groups. Functional Ecology 12: 948—958.

Roberts, BR. and V.M. Schnipke. 1987. The water requirements of ﬁve container-grown
Acer species. Hortscience 22(5):] 161-1 161.

Roussel, M., E. Dreyer, P. Montpied, G. Le-Provost, J .M. Guehl, and O. Brendel. 2009.

The drversrty of C Isotope discrlmrnatlon in a Quercus robur ﬁJll-SIb family rs
associated with differences in intrinsic water use efﬁciency, transpiration efﬁciency, and
stomatal conductance. Journal of Experimental Botany 60(8):2419-2431.

Ruter, J .M. 1998. Pot-In-Pot production and cyclic irrigation inﬂuence growth and

irrigation efﬁciency of 'Okame' cherries. Journal of Environmental Horticulture 16(3):
159-162.

136

Taiz, L. and E. Zeiger. Plant Physiology, 4th edn. Sunderland, MA: Sinauer Associates
Inc., 2006. ’

Tumbull, M.H., D. Whitehead, D.T. Tissue, W.S.F Schuster, K.J. Brown, V.C. Engel,
and KL. Grifﬁn. 2002. Photosynthetic characteristics in canopies of Quercus rubra,
Quercus prinus and Acer rubrum differ in response to soil water availability. Oecologia
130:515—524.

Tyler, H.H., S.L. Warren, and TE. Bilderback. 1996a. Cyclic irrigation increases
irrigation application efﬁciency and decreases ammonium losses. Journal of
Environmental Horticulture 14(4): 194-198.

Tyler, H. H., S. L. Warren, and TE. Bilderback. 1996b. Reduced leaching fractions
improve irrigation use efﬁciency and nutrient efﬁcacy. Journal of Environmental
Horticulture 14(4): 199-204.

Warren, S.L. and TE. Bilderback. 2002. Timing of low pressure irrigation affects plant
growth and water utilization efﬁciency. Journal of Environmental Horticulture 20(3):
1 84-1 88.

Warsaw, A.L., R.T. Fernandez, B.M. Cregg, and J .A. Andresen. 2009a. Water
conservation, growth, and water use efﬁciency of container-grown woody omamentals
irrigated based on daily water use. Hortscience 44(5): 1308-1318.

Warsaw, A.L., R.T. Fernandez, B.M. Cregg, and J A Andresen. 2009b. Container-grown
ornamental plant growth and water runoff nutrient content and volume under four
irrigation treatments. Hortscience 44(6): 1573-1580.

Witrner, R. 2000. Water use of landscape trees during pot-in-pot production and during
establishment in the landscape. Horticulture. Blacksburg, Virginia Polytechnic Institute
and State University. Doctor of Philosophy: 195.

Wright, RD. 1986. The pour-through nutrient extraction procedure. HortScience. 21 :227-
229.

Yoo, C.Y., H.E. Pence, P.M. Hasegawa, and M.V. Mickelbart. 2009. Regulation of
transpiration to improve crop water use. Critical Reviews in Plant Sciences 28: (6)410-
431.

Zhang, J. and BM Cregg. 2005. Growth and physiological responses to varied
environments among populations of Pinus ponderosa. Forest Ecology and Management
219:1-12.

137

CHAPTER FOUR

SUMMARY AND CONCLUSIONS

138

Signiﬁcance of the study

Previous research testing the effects of cyclic irrigation has been conducted mainly in the
southeastern US. or used smaller plant material (Beeson, 1992; Beeson and Haydu,
1995; Fain et al., 1999; Fare et al., 1996; Ismail et al., 2007; Keever and Cobb, 1985;
Ruter, 1998; Tyler et al., 1996). This study was designed to test the effects of cyclic
irrigation on the growth of PIP-grown coniferous and deciduous shade trees in the upper
Midwest. In addition to classifying the growth response, we explored the physiological
mechanisms controlling these growth responses. Carbon isotope discrimination is a
parameter often tested in ecological water stress research. Few horticultural studies have
used this technique to classify the water use efﬁciency of trees, as we have. Our results
will contribute to the understanding of water stress physiology of container-grown
landscape and coniferous trees and aid in the development of water-conserving irrigation
guidelines for growers in the upper Midwest.
Main results and ramifications
Deciduous Shade Trees

Seven taxa (Acerﬁeemanii ‘Jeffersred’, A. rubrum ‘F ranksred’, Gleditsia
triacanthos ‘Harve’, Gleditsia triacanthos ‘Skyline’, Quercus rubra, Ulmus ‘Morton’,
and Ulmus ‘Morton Glossy’) of bare-root liners were grown in #25 containers and
randomly assigned to varying irrigation regimes. Irrigation treatments consisted of
varying combinations of irrigation rates (low and high) and daily cycle frequencies (one
or four). Low and high irrigation rates corresponded to 1 cm and 2 cm depths,

respectively. Applications of the low irrigation rate, regardless of the number of cycles in

139

which it was applied, reduced stem radial growth of all taxa except A. freemanii and G.
triacanthos ‘Harve’ compared to the high irrigation rate.

Physiological parameters were more responsive to irrigation rate than cycle

frequency. Mid-day leaf stomatal conductance (gs) of trees irrigated cyclically was equal

to or less than trees irrigated once daily. Increasing cycle frequency only increased A of
foliar and wood tissue in A. rubrum trees. Integrated water use efﬁciency (WUE) using

carbon isotope analysis of plant tissue is a more sensitive indicator of plant water stress

than instantaneous WUE (WUEi) derived from gas exchange measurements.

Conifers
Picea glauca var. densata, Picea pungens, Abiesﬁaseri, and Pinus strobus transplants
(plug+2 or 2+2) were planted in #3 containers in a 80:20 (volumervolume) mix of pine
bark and peat moss. Also, trees of the same species grown in #3 containers from a
previous study were transplanted into #7 containers using the same media. Trees were
randomly assigned to irrigation regimes with varying combinations of irrigation rates
(low, medium, or high) and daily cycle frequencies (one or four). Low, medium, and high
irrigation rates of trees grown in #3 containers corresponded to 1 cm, 2 cm, and 3 cm
depths, respectively. Low and high irrigation rates of trees grown in #7 containers
corresponded to 1 cm and 2 cm depths, respectively.

Although stem caliper is the best single indicator of tree grth (Thompson,
1985), tree height is the parameter by which coniferous trees are most often sold in the
upper Midwest. We suggest growers integrate both measurements and use height: stem

caliper as an indicator of plant marketability. Moreover, stem caliper growth is a more

140

sensitive indicator of tree water stress than is tree height. Height growth of only P.
strobus trees increased under cyclic irrigation regimes, and irrigation rates did not affect
height growth. Stem radial grth of only P. pungens trees were affected by irrigation
rate; the low rate reduced stem radial growth compared to the high rate in both
experiments.

Physiological parameters were more responsive to irrigation rate than cycle

frequency. Mid-day gas exchange and instantaneous water use efﬁciency (WUEi) were

unaffected by irrigation treatment. A in foliar and wood tissue increased at reduced
irrigation rates. Increasing cycle frequency increased A in foliar and wood tissue.
Medium irrigation rates leached more NO3-N from containers and reduced foliar N
content of P. strobus and P. pungens trees grown in #7 containers compared to the low
rate. Trees of equal size can be produced with 50% less water than the typical irrigation

rate of 2 cm, thereby increasing proﬁtability for growers by reducing input costs.

The effect of irrigation regimes on WUE i was highly dependent on environmental

conditions. The parameter’s inconsistent response demonstrates the method’s limitations

as an accurate predictor of WUE. Within the #3 containers, the species with the highest

WUEi (P. strobus) was most capable of handling water stress and therefore did not

experience large reductions in growth as a result of water limiting irrigation regimes. We
were unable to link the growth decline of P. strobus trees in #7 containers as a result of

irrigation cycle frequency to reductions in mid-day gas exchange.

141

Reducing irrigation rates by 50% is an effective method by which growers in the
upper Midwest can conserve water and reduce input costs without sacriﬁcing growth.
Reduced foliar N levels and reductions in leachate NO3-N concentration at the 2 cm
application rate indicate that growers may leach nutrients and sacriﬁcing nutrient efﬁcacy
using these common irrigation methods. However, the decreases in stem radial growth of
P. pungens at reduced irrigation rates suggests that in some cases growers must choose
between increased nutrient retention and growth optimization.

Future research

Our results indicate that cyclic irrigation does not increase tree growth rates of coniferous
and deciduous shade trees in the upper Midwest compared to typical once-daily
applications. However, cycle frequencies other than the four times per day we tested may
be effective in reducing water stress and increasing tree grth rate. The time at which
irrigation subvolumes are applied should also be tested, as should various cycle
frequency x rate x timing combinations. Testing cyclic irrigation on a broader scale
would be helpful in assessing environmental conditions under which tree growth would
beneﬁt from increasing cycle frequency. Furthermore, determining the common
characteristics among taxa which beneﬁt from cyclic irrigation and reduced inigation
rates will allow growers to group trees based on functional characteristics and irrigate
accordingly.

Reductions in mid-day canopy temperatures associated with cyclic irrigation have
been reported in past studies (Keever and Cobb, 1985; Graves et al., 1989). This easily
measurable parameter should be included in future studies testing cyclic irrigation.

Carbon isotope discrimination, regardless of the tissue (wood or leaf) from‘which it is

142

derived, is a highly sensitive indicator of plant water stress and should be applied more

often in horticultural studies. Carbon isotope discrimination is integrative and more

reliable than WUEi measurements derived from gas exchange measurements. Because

carbon isotope analysis of tissues can be expensive (:86.50/sample), it is important to
consider the period of time over which is of interest. In studies testing the effect of water
stress over the entire growing season, it would likely be most cost-effective to select
wood tissue for carbon isotope analysis.

To fully assess the reduction in NO3-N by cyclic irrigation regimes, more extensive
collections systems must be developed. Leachate collection systems which measure total
leachate volume and leachate NO3-N concentration will more accurately quantify NO3-N
leaching from container nurseries in the upper Midwest. This will aid in quantifying the
effectiveness of water-conserving irrigation programs in reducing the environmental

impact.

143

LITERATURE CITED

Beeson, Jr., R.C. 1992. Restricting overhead irrigation to dawn limits grth in
container-grown woody omamentals. Hortscience 27(9): 996-999.

Beeson, Jr., R. C. and J. Haydu. 1995. Cyclic microirrigation in container-grown
landscape plants improves plant growth and water conservation. Journal of
Environmental Horticulture 13(1): 6-1 1 .

Fain, G. B., K.M. Tilt, C.H. Gilliam, H.G. Ponder, and J .L. Sibley. 1999. Cyclic
irrigation improves irrigation application efﬁciency and growth of sawtooth oak. Journal
of Arboriculture 25(4): 200-203.

Fare, D. C., CH. Gilliam, G.J. Keever, and RB. Reed. 1996. Cyclic irrigation and media
affect container leachate and ageratum growth. Journal of Environmental Horticulture
14(1): 17-21.

Graves, W. R., M. N. Dana, and R.J. Joly. 1989. Root-zone temperature affects water
status and growth of red maple. Journal of the American Society for Horticultural Science
114(3): 406-410.

Ismail, S.M., K. Ozawa, and N.A. Khondaker. 2007. Inﬂuence of single and multiple
water application timings on yield and water use efﬁciency in tomato (var. First Power).
Agricultural Water Management 95(2008): 116-122.

Keever, G. J. and G. S. Cobb. I985. Irrigation scheduling effects on container media and
canopy temperatures and growth of ‘Hershey Red’ azalea. Hortscience 20(5): 921-923.

Ruter, J .M. 1998. Pot-In-Pot production and cyclic irrigation inﬂuence growth and
irrigation efﬁciency of 'Okame' cherries. Journal of Environmental Horticulture 16(3):
1 59-162.

Thompson, BE. 1985. Proceedings: Evaluating seedling quality: principles, procedures,
and predictive abilities of major tests workshop. October 16-18, 1984. Forest Research
Laboratory, Oregon State University, Corvallis, OR.

Tyler, H.H., S.L. Warren, and TE. Bilderback. 1996. Cyclic irrigation increases
irrigation application efﬁciency and decreases ammonium losses. Journal of
Environmental Horticulture 14(4): 194-198.

144

 

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Figure A1 .1: Diurnal course of substrate volumetric moisture content (VWC; %) of a
subsample of 16 deciduous shade trees grown in #25 containers in a PIP facility under
varying combinations of irrigation rate (low, 1 cm or high, 2 cm) and daily cycle
frequencies (one or four) (n=4).

 

 

 

 

 

0.40
_ Low, 1x
1 1 September 2009 ................. High, 1x
A
0.35 -
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0 400 800 1200 1600 2000 2400

153

 

Figure A1.2: Mean NO3-N concentration (ppm), EC (dS/M), and pH (iSE) of pourthru
leachate samples collected in 2008 and 2009 from Acerﬁeemanii, Ulmus ‘Morton
Glossy’, and G. triacanthos ‘Skyline’ trees grown in #25 containers in a PIP production
system under varying combinations of irrigation rate (low, 1 cm or high, 2 cm) and daily
cycle frequencies (one or four) on four dates. Effect of species was not signiﬁcant. Effect
of cycle frequency was most often not signiﬁcant. Data averaged across species and cycle
frequencies (n=24). When there was a signiﬁcant cycles x rate interaction, means were
separated by treatments (n=12; * pS0.05; ** p50.01).

 

 

 

 

 

 

 

2008 2009
80
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v Low, 4x
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Sampling date
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Figure A2.1: Height growth over the two-year production cycle of four coniferous tree
species grown in #3 containers in a PIP production system under varying combinations of

irrigation rate (1, 2, or 3 cm) and cycle frequency (one or four) (n=12).

Height growth (cm)

Height growth (cm)

60

40‘

20*

 

[:1 Low

_ m Medium

m High

Cycles: ns
Rate: ns
Cycles x Rate: ns

P. glauca
#3 containers

 

 

 

 

 

60*

400

20*

Cycles: ns
Rate: ns
Cycles x Rate: ns

 

 

Cycles: ns
Rate: ns
Cycles x Rate: ns

 

P. pungens

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P. strobus

 

 

 

 

 

 

 

 

E
a

a
Cycles: ns
Rate: ns
Cycles x Rate: ns

1 4 1
Cycle frequency Cycle frequency

165

Figure A2.2: Height growth over the two-year production cycle of four coniferous tree
species grown in #7 containers in a PIP production system under varying combinations of

irrigation rate (1, 2, or 3 cm) and cycle frequency (one or four) (n=4).

Height growth (cm)

Height growth (cm)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

166

100

— Low #7 containers P. pungens

[:1 ngh P. glauca
80 —
60 ~
l i

.1:

20 ‘ CYCIQSI ns Cycles: "8

Rate: ns Rate: ns

Cycles x Rate: ns Cycles X Rate: "5

A. frasen' P. strobus
80 j
l s.-
60 ~
{1

40 -~
20 ‘ Cycles; ns CYCIESI P<0.05

Rate: ns Rate: ns

Cycles x Rate: ns Cycles x Rate: ns

0
1 4 1 4
Cycle frequency Cycle frequency

Figure A2.3: Stem radial growth over the two-year production cycle of four coniferous
tree species grown in #3 containers in a PIP production system under varying
combinations of irrigation rate (1 , 2, or 3 cm) and cycle frequency (one or four) (n=12).

 

 

 

       

 

 

 

 

 

 

 

 

 

 

 

 

25
:1 Low. ,3. glauca P. pungens
m M,ed'"m #3 containers
20 — m High
’8‘ __
E
.c 15 -
E
9
U)
r- 10 A % é;
.9-
6 l
0
5 J Cycles: ns / Cycles: "3
Rate: ns Rate: P<0.05
Cycles x Rate: ns :.:-' Cycles x Rate: ns | :5:
A. frasen‘ P. strobus
20 — __
.c 15 r
E ,
9 . ‘
a)
a 10 l - :g: 1
.9- . ;.-
E
o ‘ l -
5 jCycles: ns Cycles: ns l
l Rate: ns | Rate: ns
i Cycles x Rate: ns I . Cycles x Rate: ns _
0 y ~.-.
1 4 1 4
Cycle frequency Cycle frequency

167

Figure A2.4: Diurnal course of net photosynthesis (Amax; mol-m-z-s-l), canopy
temperature (C), and instantaneous water use efﬁciency (WUEi; Amax/gs) (iSE) of A.
fraseri trees grown in #7 containers on 5 August 2009 in a PIP production system under
varying combinations of irrigation rate (1 or 2 cm) and daily cycle frequencies (one or
four). Mean diurnal canopy temperature was reduced when trees received the high rate or
cyclic irrigation compared to the low rate or once daily applications, respectively
(a=0.05; n=4).

20

 

+ Low, 1xlday
—0— High, 1xlday
+ Low, 4x/day
High, 4x/day

16*

    

12*

Amax
a)

. Cycles: ns
Rate: ns
‘ Cycles x Rate: ns

 

30‘
28‘
264
24‘

Canopy temperature

22 .

Cycles: P<0.01
20 J Rate: P<0.05
Cycles x Rate: ns

 

80-

60‘

WUEi

40‘

 

20 « Cycles: ns
Rate: ns
Cycles x Rate: ns

 

 

 

0 I
800 1000 1200 1400 1600 1800 2000 2200

Time

I I I

168

Figure A2.5: A values ($813) of 2008 and 2009 needles of four coniferous tree species
grown in #3 containers in a PIP production system under varying combinations of
irrigation rate (I or 3 cm) and daily cycle frequencies (one or four) (a=0.05; n=6).

A (%o)

A (%o)

A (%o)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

32 2008 2009
Cycles: ns P, glauca Cycles: ns P, glauca
Rate: ns Rate: P<0.05
3° * Cycles x Rate: ns Cycles x Rate: ns
28 . f 5 E
26 d - Low
[:3 High
Cycles: "8 P. pungens CYC'955 P<0-01 P. pungens
Rate: ns Rate: ns
30 ‘ Cycles x Rate: ns Cycles x Rate: P<0.05
55 5‘3 E E
28 a -
26 4
Cycles: ns - Cycles: ns .
Rate: "S A. frasen Rate: "s A. frasen
3° ‘ Cycles x Rate: ns Cycles x Rate: ns
5
23 . SE E I.
26 ~
24
1 4 Cycles: ns P. strobus
y eq y 30 ‘ Cycles x Rate: ns
33
A 28 "‘
2%
<1 26 -

 

 

 

 

169

Iii I4

Cycle frequency

 

Figure A2.6: A values (iSE) of 2008 and 2009 wood of four coniferous tree species
grown in #3 containers in a PIP production system under varying combinations of
irrigation rate (1 or 3 cm) and daily cycle frequencies (one or four) (a=0.05; n=6).

A (%o)

A (%o)

A (%o)

A (%o)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

29 2008 2009
CYC'eS3 "5 P. Iauca CYC'eS3 "5 P. Iauca
28 J Rate: P<0.05 9 Rate: P<0.01 g
27 Cycles x Rate: P<0.05 Cycles x Rate: ns
1
26 - 3:- a i
25 1
24 ﬂ - Low
[:1 High
CycleSI Us P. pungens CYC'GSI P<0-01 P. pungens
28 - Rate: ns Rate: ns
Cycles x Rate: ns Cycles x Rate: ns
27 " E‘ E
26 1 :E E
25 4
24 ~
Cycles: ns VA. fraseri CYC'353 P<0-05 A, fraseri
28 - Rate: ns Rate: ns
27 _ Cycles x Rate: ns Cycles X Rate: "5
35 _
26 « I i
25 a
24 -
Cycles: ns p. strobus Cycles: P<0.05 p. strobus
28 - Rate: ns Rate: P<0.01
27 Cycles x Rate: ns Cycles x Rate: ns
i
26 — at.
25 .
2- . I
23 *
1 4 1 4
Cycle frequency Cycle frequency

170

 

Figure A2.7: A values (iSE) of 2008 and 2009 foliar tissue of four coniferous tree
species grown in #7 containers in a PIP production system under varying combinations of
irrigation rate (1 or 2 cm) and daily cycle frequencies (one or four) (a=0.05; n=4).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

32 2008 2009
Cycles: ns P. glauca Cycles: ns P, glauca
Rate: ns Rate: P<0.05
30 ' Cycles x Rate: ns Cycles x Rate: ns
A E
g 28 ~ f i "
<1
26 i — Low
[:1 High
Cycles: ns (31/6'93: P<0-05 P. un ens
Rate: ns P' p ung ens Rate: P<0.01 p g
30 * Cycles x Rate: ns ﬂ Cycles x Rate: ns
3? :E
v 28 ‘
<1
26 ~
Cycles: ns A fraseri CYC'933 "5 A. frasen'
Rate: ns ' Rate: P<0.05
3o - Cycles x Rate: ns Cycles x Rate: ns
33 28 « E g __
<1
26 -
24
1 4 P. strobus
Cycle frequency 30 _
’3 28 -
2‘;
4 ii iii
1 4

Cycle frequency

171

Figure A2.8: Nitrate-N concentration (ppm), EC (dS/M), and pH (28E) of pourthru
leachate samples collected in 2008 and 2009 from P. strobus and A. fraseri trees grown
in #3 containers in a PIP production system under varying combinations of irrigation rate
(1, 2, or 3 cm) and daily cycle frequencies (one or four) (n=l6). Effect of cycles was not
signiﬁcant; data averaged across species and cycle frequency (n=12). Means with
different letters are different at p50.05; "5 nonsigniﬁcant.

 

160
+ Low #3 containers

140 ~ —0— Medium
-7- th
120 -

N03' N (ppm)
on
o

 

 

 

 

7.5 a

7.0 -‘

pH

6.5 -.

6.0 0

 

2.5 a

2.0 :

 

EC (dS/M)

1.5 ~
. §—_ -‘
1.0 § \§

0.5

 

 

 

 

 

7

3 Jul 22 Jul 3 Sept 14 May 20 Jun 21 Jul
2008 2009
172

 

 

Figure A2.9: NO3-N concentration (ppm), EC (dS/M), and pH (iSE) of pourthru leachate
samples collected in 2008 and 2009 from P. strobus and A. ﬁaseri trees grown in #7
containers in a PIP production system under varying combinations of irrigation rate (1 or
2 cm) and daily cycle frequencies (1 or 4). Effect of cycles was not signiﬁcant; data
averaged across species and cycle frequency (n=12). Means with different letters are
different at p50.05; “5 nonsigniﬁcant.

2008 2009

 

160

I L5“ #7 containers
140 1 ’O- ngh
120 1
100 -

806

NO3-N (ppm)

60-

 

40*

 

20*

 

8.0 - —--—«-
7.5 « ,§~0\%

7.0 ~

pH

6.5 1

 

6.0 -‘

 

5.5 q

t

2.5 a

2.0 ~

 

EC (dS/M)

1.5 r

1.0 ~

 

 

 

 

0.5 - - - , . A
3 Jul 22 Jul 3 Sept 14 May 20 Jun 21 Jul

173

    

 
 

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3 129