IRRIGATION MANAGEMENT AND ALTERNATIVE CONTAINERS FOR MORE
SUSTAINABLE NURSERY PRODUCTION
By
Xueni Wang

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
Horticulture – Master of Science
2013

ABSTRACT
IRRIGATION MANAGEMENT AND ALTERNATIVE CONTAINERS FOR MORE
SUSTAINABLE NURSERY PRODUCTION
By
Xueni Wang

Reducing the use of water and plastics in nursery production can have a large impact on
the sustainability of a nursery operation. Container-grown woody ornamentals were irrigated at
four different levels based on daily water use (DWU) to study the impact on plant growth,
leachate electrical conductivity, pH, runoff water volume and nutrient loss. For all taxa, final
growth index, leachate electrical conductivity (EC), pH, runoff water volume, runoff NO3- and
PO43- concentration were similar under all treatments. Water runoff volume and nutrient loss
were much lower than the conventional nursery irrigation volume used by Warsaw et al., 2009.
Alternative containers were evaluated to compare water use, plant growth, leachate EC, pH, root
zone temperature and container physical properties and biodegradability compared to
conventional plastic containers. Container type did not affect final plant growth index, leachate
EC or pH. The seasonal mean substrate temperature in all alternative containers was lower than
that of plastic containers. Paper fiber containers used more water than plastic containers in 2011;
however plastic containers had the greater water use than alternative containers in 2012. All
alternative containers tested passed the germination tests for biodegradability according to
ASTM D6868, 6400 and D5338. Alternative containers tested were not proven to be
biodegradable according to the ASTM D 5338 standard.

ACKNOWLEDGEMENT

I am deeply grateful for the valuable guidance, support and expertise from my major
professor, Dr. Tom Fernandez. Thank you for the opportunity to study abroad and work with
you. I would also like to thank my committee members Dr. Bert Cregg and Dr. Rafael Auras for
their help and time during the research. My thanks also go to Dr. Bridget Behe and Dr. Randy
Beaudry for their mentoring and help.
I thank Bill Chase, Gary Winchell and the staff at Horticulture Teaching and Research Center
for their help and generosity with their time and tools. Aaron Lynn-Vogel, Christina Horrigan,
James Rauschendorfer, Mark Alanson, Jessi Orme, Santos Hernandez and Josh Getter helped me
immensely for data collection and field plot maintaining, thank you to you all. I would like to
express my gratitude towards my officemates and colleagues Ning Gong, Nick Pershey, Brent
Crain, Heidi Wollaeger, Bill Linberg, Chia-Hong Tsai, Wei-Kuang Lin, Qingwu Meng, and Nate
DuRussel for your friendship, help and encouragement. A special thank goes to Gary Meloeny,
thank you for your time discussing my thesis with me. I would like to give thanks to all the
people in the horticulture office and department for your help and kindness, you made this
department a delightful place.
Finally and most importantly, I’d like to thank my parents, Mom and Dad, thank you for
your continuous love and support throughout my grad school time.

iii

TABLE OF CONTENTS

LIST OF TABLES ........................................................................................................................ vii
LIST OF FIGURES .........................................................................................................................x
LITERATURE REVIEW ................................................................................................................1
Alternative Container Evaluation ....................................................................................................2
Horticultural Container Overview ...............................................................................................2
Agricultural Plastic Waste Disposal and Recycling....................................................................3
Types of Alternative Containers and Their Properties ................................................................5
Consumers’ Willingness to Pay and Growers’ Acceptance ........................................................6
Plant Growth and Water Use in Alternative Containers .............................................................7
Woody Ornamental Irrigation Management ....................................................................................9
Introduction .................................................................................................................................9
Container Nursery Irrigation Overview ....................................................................................10
Current Irrigation Systems ........................................................................................................12
Overhead Irrigation ..............................................................................................................12
Micro Irrigation ....................................................................................................................13
Irrigation Efficiency ..................................................................................................................13
Cyclic Irrigation....................................................................................................................14
Leaching Fractions ...............................................................................................................16
Management Allowed Deficit Irrigation ..............................................................................17
Precision Irrigation Based on Evapotranspiration and Plant Water Demand.......................17
Soil Moisture Content Measurement Methods .........................................................................19
Time Domain Reflectometer ................................................................................................19
Capacitance Sensors .............................................................................................................20
LITERATURE CITED ..................................................................................................................22

CHAPTER ONE
GROWTH AND WATER USE OF TEN WOODY ORNAMENTALS UNDER FOUR
IRRIGATION REGIMES ..............................................................................................................31
Abstract .....................................................................................................................................32
Introduction ...............................................................................................................................34
Material and Methods ...............................................................................................................35
Site specifications .................................................................................................................35
Experimental design .............................................................................................................35
Plant material and culture .....................................................................................................36
Irrigation treatment application ............................................................................................37
Daily water use .....................................................................................................................38
Plant growth..........................................................................................................................38
Leachate electrical conductivity and pH ..............................................................................38
Water use efficiency (WUE) and crop coefficient (Kc) .......................................................39
iv

Runoff water collection ........................................................................................................39
Statistical analysis ................................................................................................................40
Results and Discussion ..............................................................................................................40
Water applied 2011 and 2012 ...............................................................................................40
Growth index (GI) ................................................................................................................46
WUE .....................................................................................................................................46
DWU.....................................................................................................................................49
Leachate EC..........................................................................................................................57
Leachate pH ..........................................................................................................................57
Nutrient loss and runoff ........................................................................................................60
Conclusions ...............................................................................................................................62
LITERATURE CITED ..................................................................................................................63

CHAPTER TWO
PHYSICAL PROPERTIES AND COMPOSTABILITY OF ALTERNATIVE CONTAINERS
FOR NURSERY PRODUCTION .................................................................................................66
Abstract .....................................................................................................................................67
Introduction ...............................................................................................................................68
Material and Methods ...............................................................................................................70
Site specifications and plant material ...................................................................................70
Experimental design .............................................................................................................72
Container physical properties ...............................................................................................74
Fourier transform infrared spectroscopy (FTIR) ..................................................................75
Compostability .....................................................................................................................76
Statistical analysis ................................................................................................................77
Results and Discussion ..............................................................................................................78
Compression strength ...........................................................................................................78
Tensile strength of RP containers .........................................................................................80
Water vapor transmission rate (WVTR)...............................................................................80
FTIR .....................................................................................................................................82
Compostability .....................................................................................................................85
Conclusions ...............................................................................................................................91
LITERATURE CITED ..................................................................................................................92

CHAPTER THREE
PLANT GROWTH AND WATER USE IN ALTERNATIVE CONTAINERS FOR NURSERY
PRODUCTION ..............................................................................................................................95
Abstract .....................................................................................................................................96
Introduction ...............................................................................................................................97
Material and Methods ...............................................................................................................99
Site specifications and experimental design .........................................................................99
Plant material and treatments ...............................................................................................99
Irrigation application and daily water use (DWU) .............................................................100
v

Plant growth index and biomass .........................................................................................101
Leachate EC, pH and root zone temperature ......................................................................101
Statistical analysis ..............................................................................................................102
Results and Discussion ............................................................................................................102
DWU...................................................................................................................................102
Plant growth and biomass ...................................................................................................104
Root zone temperature ........................................................................................................107
Leachate EC and pH ...........................................................................................................110
Conclusions .............................................................................................................................112
LITERATURE CITED ................................................................................................................113

CHAPTER FOUR
CONCLUSIONS AND FUTURE DIRECTION OF CONTAINER NURSERY IRRIGATION
MANAGEMENT AND ALTERNATIVE CONTAINERS ........................................................115
Woody Ornamental Irrigation Management ...........................................................................116
Alternative Containers ............................................................................................................118
Future Research .......................................................................................................................120
LITERATURE CITED ................................................................................................................122

vi

LIST OF TABLES

Table 1.1. Container-grown woody ornamentals grown in the 2011 and 2012 irrigation
experiments ....................................................................................................................................37
Table 1.2. Daily water applied averaged over the season and seasonal total water applied from 23
June through 2 Nov. 2011 (133 d) for all plants. Plants were grown in 10.2-L containers under
four irrigation treatments. 100DWU = irrigation scheduled to replace 100% DWU per
application; 100-75 = irrigation alternating every other application with 100% replacement of
DWU and 75% DWU the following application; 100-75-75 = irrigation scheduled on a threeapplication cycle replacing 100% DWU followed by two applications replacing 75% DWU; 10075-75-75 = irrigation scheduled on a four-application cycle replacing 100% DWU followed by
three applications replacing 75% DWU. Irrigation volume applied = highest DWU of the four
species on each measurement day. Irrigation applications separated by at least 24h. Means
separation using Tukey’s test (𝛼 =0.05), n=133. Means with same letters are not significantly
different (α=0.05) ...........................................................................................................................42
Table 1.3. Estimated water use efficiency (WUE) and GI increment of three container-grown
woody ornamentals under four irrigation regimes from June 21 to Sep 27, 2011. WUE estimated
as increase in growth index (cm) per liter of water per container. 100DWU = irrigation scheduled
to replace 100% DWU per application; 100-75 = irrigation alternating every other application
with 100% replacement of DWU and 75% DWU; 100-75-75 = irrigation scheduled on a threeapplication cycle replacing 100% DWU followed by two applications replacing 75% DWU; 10075-75-75 = irrigation scheduled on a four-application cycle replacing 100% DWU followed by
three applications replacing 75% DWU. DWU volume applied based on the highest DWU of the
four species on each measurement day. Irrigation applications separated by at least 24h. Liters
per container from 21 June to 27 Sep. 2011. Means with same lowercase letters within the same
row are not significantly different. Means with same uppercase letters within the same column
are not significantly different. Means separation with Tukey’s test (α= 0.05). GI= growth
index...............................................................................................................................................47

Table 1.4. WUE and GI increment of five container-grown woody ornamentals under four
irrigation regimes from June 26 to Oct 11, 2012. WUE estimated as increase in growth index
(cm) per liter of water per container. 100DWU = irrigation scheduled to replace 100% DWU per
application; 100-75 = irrigation alternating every other application with 100% replacement of
DWU and 75% DWU the following application; 100-75-75 = irrigation scheduled on a threeapplication cycle replacing 100% DWU followed by two applications replacing 75% DWU; 10075-75-75 = irrigation scheduled on a four-application cycle replacing 100% DWU followed by
three applications replacing 75% DWU. Irrigation volume applied = highest DWU of the four
species on each measurement day. Irrigation applications separated by at least 24h. Liters per
container from 26 June to 11 Oct. 2012. Means with same letters within the same column are not
significantly different. Means separation with Tukey’s test (𝛼 =0.05).GI= growth index ............49

vii

Table 1.5. Crop Coefficient of ten woody ornamental taxa in 2011 and 2012 ..............................56
Table 1.6. Average seasonal runoff PO43- -P and NO3- –N load under four irrigation treatments.
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three applications
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h. Means with same letters are
not significantly different (α=0.05) ................................................................................................61
Table 2.1. Container treatments used in 2011 and 2012 alternative container studies ..................73
Table 2.2. Tensile strength test result of root pouch container under field condition for 0, 2, 6 and
12 months. Means with the same letter in the same column is not significantly different (α=0.05) .
........................................................................................................................................................80
Table 2.3. Water Vapor Transmission Rate (WVTR) of Kord and Western pulp (WP) container
under field conditions from June 2010 to June 2011 for month 0, 2, 6 and 12. Means with the
same lowercase letter in the same row are not significantly different (α=0.05). Means with the
same uppercase letter in the same column are not significantly different (α=0.05) .....................81
Table 2.4. Water Vapor Transmission Rates (WVTR) of Western pulp (WP), Root pouch (RP),
and Keratin (KR) containers from June 2011 to June 2012 for month 0, 2, 6 and 12. Means with
the same lowercase letter in the same row are not significantly different (α=0.05). Means with
the same uppercase letter in the same column are not significantly different (α=0.05) ...............81
Table 2.5. Heavy mental concentration result of Kord containers ................................................89
Table 2.6. Heavy mental concentration result of Western pulp containers ...................................89
Table 2.7. Onion and cucumber seed germination rate in control compost (compost only) and final
compost containing Kord fiber pot or Western pulp (WP) containers including 5 replicates, average
germination rate and percentage comparing to that of control compost in 2011...........................90
Table 2.8. Oat and cucumber seed germination rate in control compost (compost only) and final
compost containing Western pulp (WP), Keratin (KR) and Root pouch (RP) containers including
5 replicates, average germination rate and the percentage comparing to that of control compost in
2012................................................................................................................................................90
Table 3.1. Leaves, stem, and root dry weight of Euonymus fortunei grown in Plastic, Western
pulp (WP), and Kord containers on June 6, 2011. Means with the same letter in the same column
are not different (α=0.05) .............................................................................................................106

viii

Table 3.2. Leaves, stem, and root dry weight of Buxus x ‘Green Velvet’ grown in Plastic, Western
pulp (WP), Root pouch (RP) and Keratin (KR) containers on June 14, 2012. Means with the same
letter in the same column are not different (α=0.05) ...................................................................106

ix

LIST OF FIGURES

Figure 1.1 A-D. Daily irrigation volume applied to containerized woody ornamental plants under
four irrigation treatments showing seasonal patterns from 23 June (Day 0) to 2 Nov, 2011.
z
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h. .............................................43
Figure 1.2 A-D. Daily irrigation volume applied to containerized woody ornamental plants under
four irrigation treatments showing seasonal patterns from 26 June (Day 0) to 13 Oct, 2012.
z
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h. .............................................44
Figure 1.3. Referential potential evapotranspiration rate (RPET) of 2011 and 2012 from 23 June
to 2 Nov, 2011 and 2012. Data recorded at an Enviro-weather weather station located at the
Michigan State University Horticulture Teaching and Research Center .......................................45
Figure 1.4. Daily water use (DWU) from 23 June through 2 Nov. 2011 (133 d) for Hibiscus
syriacus ‘Bricotts’, Euonymus alatus ‘Select’, Weigela florida ‘Alexandra’, Spiraea japonica
‘Yan’ grown in 10.2-L containers under four irrigation treatments.100DWU = irrigation
scheduled to replace 100% DWU per application; 100-75 = irrigation alternating every other
application with 100% replacement of DWU and 75% DWU the following application; 100-7575 = irrigation scheduled on a three-application cycle replacing 100% DWU followed by two
applications replacing 75% DWU; 100-75-75-75 = irrigation scheduled on a four-application
cycle replacing 100% DWU followed by three application replacing 75% DWU. Irrigation
volume applied = highest DWU of the four species on each measurement day. Irrigation
applications separated by at least 24h. Means for each taxa with the same letters are not
significantly different from each other. Mean separated by t-test (p=0.05). n =18. Error bars
represent standard error of means from 18 plants of each species ................................................51
Figure 1.5. Daily water use (DWU) of Viburnum dentatum ‘Ralph Senior’, Juniperus
horizontalis ’Hegedus’, Potentilla fruticosa ‘Lundy’, Hydrangea paniculata ‘Limelight’, Thuja
occidentalis ‘Sunkist’, Hypericum x ‘Cfflpc-1’ grown in 10.2-L containers under four irrigation
treatments from June 26, 2012 to October 13, 2012. 100DWU = irrigation scheduled to replace
100% DWU per application; 100-75 = irrigation alternating every other application with 100%
x

replacement of DWU and 75% DWU the following application; 100-75-75 = irrigation
scheduled on a three-application cycle replacing 100% DWU followed by two applications
replacing 75% DWU; 100-75-75-75 = irrigation scheduled on a four-application cycle replacing
100% DWU followed by three application replacing 75% DWU. Irrigation volume applied =
highest DWU of the four species on each measurement day. Irrigation applications separated by
at least 24h. Means for each taxa with the same letters are not significantly different from each
other. Mean separated by t-test (p=0.05). n =18. Error bars represent standard error of means
from 18 plants of each species. ......................................................................................................52

Figure 1.6 A-D. Daily water use (DWU) from June 23, 2011 to Nov 2, 2011 for Hibiscus
syriacus ‘Bricotts’, Euonymus alatus ‘Select’, Weigela florida ‘Alexandra’, Spiraea japonica
‘Yan’ grown in 10.2-L containers under 100DWU irrigation treatment. ......................................53
Figure 1.7 A-F. Daily water use (DWU) of Viburnum dentatum ‘Ralph Senior’, Juniperus
horizontalis ’Hegedus’, Potentilla fruticosa ‘Lundy’, Hydrangea paniculata ‘Limelight’, Thuja
occidentalis ‘Sunkist’, Hypericum x ‘Cfflpc-1’ grown in 10.2-L containers under 100DWU
irrigation treatment and PET from 26 June to 13 Oct, 2012 ..........................................................54
Figure 1.8 A-F. Leachate pH for Viburnum dentatum ‘Ralph Senior’, Juniperus
horizontalis ’Hegedus’, Potentilla fruticosa ‘Lundy’, Hydrangea paniculata ‘Limelight’, Thuja
occidentalis ‘Sunkist’, Hypericum x ‘Cfflpc-1’ grown in 10.2-L containers under four irrigation
treatments on experimental day 6, 41, 72 and 100. 100DWU = irrigation scheduled to replace
100% DWU per application; 100-75 = irrigation alternating every other application with 100%
replacement of DWU and 75% DWU the following application; 100-75-75 = irrigation
scheduled on a three-application cycle replacing 100% DWU followed by two applications
replacing 75% DWU; 100-75-75-75 = irrigation scheduled on a four-application cycle replacing
100% DWU followed by three application replacing 75% DWU. Irrigation volume applied =
highest DWU of the four species on each measurement day. Irrigation applications separated by
at least 24h. Means within taxa with the same letters are not significantly different between
treatments. Mean separated by tukey’s t-test (α=0.05). n =18. ns = no significance ....................59
Figure 2.1. Air temperature (A), relative humidity (B) and solar radiation (C) at the Michigan
State University Horticulture Teaching and Research Center weather station from June 2011 to
June 2013 .......................................................................................................................................71
Figure 2.2. The compression strength for Kord fiber (Kord) and Western pulp (WP) containers
from May 2011 to May 2012 .........................................................................................................79
Figure 2.3. The compression strength for Western pulp (WP), Plastic and Keratin (KR)
containers from June 2012 to June 2013.NS = No significance ....................................................79
Figure 2.4. Fourier transform infrared spectroscopy of Western pulp containers outside wall of
experimental month 0, 4, 8 and 12 in 2011....................................................................................83

xi

Figure 2.5. Fourier transform infrared spectroscopy of Kord containers outside wall of
experimental month 0, 4, 8 and 12 in 2011....................................................................................84
Figure 2.6. Mineralization ratio of Western pulp (WP), Kord container comparing to cellulose
powder in manure compost at 58℃ and 55% relative humidity during 50 day of direct
measurement respirometric experiment .........................................................................................86
Figure 2.7. Percent Mineralization of cellulose powder, Keratin (KR), Root pouch (RP) and
Western pulp (WP) container in manure compost at 58℃ and 55% relative humidity during 90
days of direct measurement respirometric experiment ..................................................................87
Figure 3.1. Daily water use (DWU) of Euonymus fortunei grown in western pulp (WP), Kord
fiber (Kord) and Plastic containers from June 16, 2011 (Day 0) to Oct 26, 2011. All plants were
irrigated to replace total DWU back to the container ..................................................................103
Figure 3.2. Daily water use (DWU) of Buxus x 'Green Velvet' grown in western pulp (WP),
keratin (KR), Plastic and root pouch (RP) containers from June 23, 2012 (Day 0) to Oct 28,
2012. All plants were irrigated to replace DWU back to the container. ......................................104
Figure 3.3. Substrate temperature in Western Pulp (WP), Kord fiber(Kord) and Plastic containers
located at Horticulture Teaching and Research Center (Holt, MI) from July 20 (Day 0), 2011 to
Oct 27, 2011. Daily average temperature (A) daily maximum temperature (B), daily minimum
temperature(C) .............................................................................................................................108
Figure 3.4. Substrate temperature in Western Pulp (WP), Plastic, keratin (KR) and Root Pouch
(RP) containers from June 10 (Day 0) to Oct 29 (Day 143), 2012. Daily average temperature (A),
daily maximum temperature (B), daily minimum temperature (C) .............................................109
Figure 3.5. Leachate EC (ms· -1) and pH from Buxus x ‘Green Velvet’ grown in Western pulp,
cm
Keratin, Plastic and Root pouch containers on Experiment day 23, 42, 57, 85, 116 and 114 (day
0=May 14, 2012). Means with the same letter within the same date are not different (α=0.05)
......................................................................................................................................................111

xii

LITERATURE REVIEW

1

Alternative Container Evaluation
Horticultural Container Overview
The environmental horticulture industry has been recorded as one of the fastest
expanding sectors of the nation’s agriculture, and it comprises floriculture, greenhouses, nursery
and turf grass sod production (Yue et al., 2010). Within this industry, nursery and greenhouse
production sectors alone created 436,462 jobs and $ 27.1 billion in 2007-08 (Hodges et al.,
2011). Plastic containers are the most commonly used pots for container production in nursery
and greenhouse operations. In nine southern US states, the containers purchased by growers
totaled $ 16.6 million, 99% of those were polyethylene (Hodges and Haydu, 2001). The
attributes of light weight and low cost of polyethylene containers are advantages for horticultural
use (Amidon, 1994); however, there are many problems associated with plastic containers.
Disposal of plastic containers can cause environmental issues such as toxic gas
emission from burning and landfill space occupation (Anand et al., 2007). The most overriding
concern is that plastic container production is not sustainable, since approximately 4 percent of
annual petroleum resources are used to make plastic and a similar amount of petroleum is used to
provide energy for the production process (Thompson et al., 2009). Yet the containers are rarely
recycled and usually disposed of after the first use (Evans and Hensley, 2004). In order to
address these issues, new materials are being sought for biodegradable and compostable
containers such as bioresins, coir, poultry feathers, paper fibers, rice hulls and processed cow
manure (Evans and Hensley, 2004; Hall et al., 2010b). Biodegradable and compostable materials
mean that the object will be broken down by natural occurring microorganisms (ASTM, 2004).
Biodegradable materials might contain toxins while compostable materials must break down into
carbon dioxide, water and biomass that is not toxic. In other words, compostable materials by

2

definition are biodegradable while biodegradable materials are not necessarily compostable
(Kale et al., 2007).
Limited literature has been published associating the physical properties of alternative
containers and their effects on plant growth and water usage. This review will address the
following topics related to alternative container background, marketing research and evaluation:
1. Agriculture plastic waste disposal and recycling
2. Types of alternative containers and their properties
3. Consumers’ willingness to pay and growers’ acceptance
4. Plant growth and water use in alternative containers

Agricultural Plastic Waste Disposal and Recycling
The nursery industry switched from in-ground production to above-ground container
production system during the 1950s as container-grown plants are easier and less expensive to
harvest and ship (Yue et al., 2010). Plastic containers are usually made from injection-molded or
blow molded high density polypropylene. Compared to once conventional clay pots, plastic
containers are lighter weight, stronger and have greater moisture preservation (Larson, 1993).
Due to the favorable characteristics of plastic containers and widespread use, the industry is
generating a huge amount of plastic waste each year. Amidon (1994) indicated that in 1992 the
Unites States used 236 million kg of agricultural plastic and the majority of this plastic was in
the form of nursery containers. Levitan and Barros (2003) provided an estimation of 1.678
billion pounds of plastic used in the global agriculture sector in 2002, under the assumption that
3% of the plastic sold was for agriculture use.

3

The current primary disposal methods of plastic containers include landfill burial, incineration,
recycling and reuse. Landfill burial is the traditional disposal approach for postconsumer plastic
containers; however the landfill space is sparse in some countries and several European countries
have imposed landfill bans on combustible waste such as plastic since 1996 (Olofsson et al.,
2005). Because plastic has only been produced in large quantities for approximately 60 years, its
life cycle in the environment is unknown (Hopewell et al., 2009), therefore, long term risks of
soil and groundwater contamination could result from UV stabilizers and additives in the plastic
products (Teuten et al., 2009). Moreover, many containers purchased for agricultural use come
in contact with pesticides and fertilizers (Hemphill, 1993) and may retain residues which could
also add to contamination risks. Incineration reduces the landfill space needed for plastic waste,
yet plastic burning could cause environmental problems such as emission of carbon dioxide,
which adds to global warming and the release of toxic gases into the atmosphere (Anand et al.,
2007; Astrup et al., 2009; Hopewell et al., 2009). As finding new disposal options becomes more
difficult, alternatives to disposal have been sought such as recycling the plastic. Although
recycling creates a positive public attitude toward generated waste, the impact has been limited
(Sakai et al., 1996). Due to several causes, the recycling percent of plastic in 2009 was only 7.9%
(Environmental Protection Agency, 2010). First, the plastic product often contains toxic dyes
and stabilizers which makes recycling a limited option (Hemphill, 1993). Secondly, many
recycling facilities are often unwilling to accept plastics with soil or media residues and shipping
and processing fees increase with contamination (Garthe and Kowal, 1993). Additionally, some
professional growers have concerns about plant pest outbreaks by reusing pots even after using
sanitation practices (Yue et al., 2010). In order to address these issues, significant effort has been
made to develop containers from alternative materials (Evans and Hensley, 2004).

4

Types of Alternative Containers and Their Properties
Numerous alternative containers had been developed to meet the needs of bio-sensitive
consumers and growers, including containers made from peat, bioresins, poultry feathers, wood
fiber, paper fiber, rice hull, coir and cow manure compost (Evans and Karcher, 2004; Grayed,
1971; Kuehny et al., 2011; Lopez and Camberato, 2011)
Limited research has been published regarding the physical properties of alternative
containers. Evans and Karcher (2004) evaluated the dry and wet strength of plastic, peat and
feather fiber containers by increasing the amount of pressure on the container using a texture
analyzer; they discovered that peat and feather fiber containers had lower dry and wet strength
than plastic containers. Moreover, the wet strength was much lower than the dry strength for
both containers. Candido et al.(2007) evaluated the tensile strength behavior and chromatic
character of traditional polypropylene containers and biodegradable plastic containers during a
five month experiment in the greenhouse, finding that the tensile strength of biodegradable
plastic containers decreased over time, and all pots except traditional ones exhibited
discoloration and concluded they were not suitable for horticultural production. Schettini et al.
(2012) tested the physic-chemical characterization of containers made from tomato and hemp
fibers with mechanical, water vapor permeability, and morphological analysis. They discovered
that the biodegradable pots allowed dense root development and did not cause any transplant
shock or root deformation.
Several studies have been done to test the biodegradability or decomposition ratio of
containers currently on the market. Candido et al. (2007) evaluated pot degradation by visual
assessment, finding containers made from biodegradable plastic with 10% and 20% compostable
materials are not suitable for Poinsettia cultivation as their mechanical resistance decreased too

5

rapidly over time within the production period. Ahn et al. (2011) tested the biodegradability of
pots containing polylactic acid and poultry feather fiber by measuring the CO2 produced during
incubation; they also used near infrared spectroscopy to estimate the chemical compounds of the
pot material that led to degradation. They found that the poultry feather fiber did not degrade
during the compost period but the polyactic acid underwent chemical changes during polymer
extruding and molding, which prohibits biodegradation.

Consumers’ Willingness to pay and Growers’ Acceptance
Several studies have investigated consumers’ attitudes toward environmentally friendly
packaging. Coddington (1990) reported that in 1986, 67% of U.S. consumers said that they were
willing to pay 5%-10% more for recyclable or biodegradable packaging. Consumers increasingly
value environmentally friendly product packaging and this has carried over to the horticulture
sector in the forms of biodegradable containers. Yue et al. (2010) conducted research on
consumers’ willingness to pay for plastic containers and biodegradable containers; they reported
that consumers are willing to pay a premium for biodegradable containers but the amount differs
by material. The highest premium consumers were willing to pay for rice hull pots, straw pots
and wheat starch pots were $0.58, $0.37, and $0.20 per pot compared to traditional plastic pots,
respectively. Behe et al. (2013) investigated consumers’ preferences for local plant production,
finding that 17 % of the consumers were mostly influenced by the container type, plant type and
the compostable character of the pot compared to other aspects such as conventional, plantable
and recyclable pots. In order to better understand consumers’ behavior towards biodegradable
containers, several market segments : “Rice Hull Likers”, “Straw Likers”, “Price Conscious”,
“Environmentally Conscious“, “Carbon Sensitive” and corresponding consumer information
6

were identified (Hall et al., 2010b). Additionally, Hall et al. (2010b) pointed out that consumers
were reluctant to purchase low-quality products with green attributes, so they needed to be
convinced these were better or equal to the non-green products.
Growers are willing to adopt biodegradable containers as part of their sustainable production
practices. In a survey conducted by the Ohio Florist Association, 95% of U.S. growers had heard
about sustainable floriculture and 65.2% value this as “very important” to the environment;
63.1% of the growers had used sustainable practices in daily operations and 24.3% are in the
process of becoming sustainable (Hall et al., 2009). Lopez et al. (2008) stated that adopting
alternative containers is one important step for a growers’ operations to become sustainable.
Converting from plastic containers to biodegradable containers does not only result in
becoming more environmentally sustainable, but also could be profitable. Hall et al. (2010a)
conducted a financial feasibility analysis of converting from plastic containers to Elle pots,
which is a production system that wraps a paper fabric around growing substrate. He found that
the net present value for growers who bought a new Elle pot machine and used recommended
growing substrate would range from $26,763 to $28, 852 based on a 15 year loan based on a 0.8
ha greenhouse.

Plant Growth and Water Use in Alternative Containers
Several experiments have been done to compare plant growth and water use in alternative
containers. Evans and Hensley (2004) found that when vinca and impatiens were irrigated
according to plant needs, plants grown in poultry feather and peat containers required more
irrigation than plastic containers. They also reported that the dry shoot weight of impatiens and
vinca plants in poultry feather containers were greater than that grown in peat and plastic

7

containers when irrigated according to plant needs. Keuhny et al. (2011) conducted a similar
experiment, evaluating geranium, vinca and impatiens growth in seven alternative containers
including 10 cm or 12.7 cm wood pulp pots, cow pots, coir, peat, rice hull, paper, and bioplastic
containers and plastic containers at five locations. They reported that the growth of geranium,
impatiens and vinca varied by location and container type, however, those plants grown in 5 inch
plastic or paper containers basically had better growth than other container types. Minuto et al.
(2007) found that sweet basil, rosemary, sages, thymus, cyclamen, daisy and lavender grown in
biodegradable containers called Master –Bi had similar growth rate to those in normal plastic
containers. Lopez and Camberato (2011) evaluated Poinsettia growth in alternative containers
and plastic containers, finding Poinsettias grown in molded paper fiber containers had better
growth compared to wheat starch-derived bioresins and plastic containers.
The research above indicates that, in general, plants grown in biodegradable containers have
similar or better growth than plants grown in plastic containers when the water supply is
sufficient. Yet there are no experiments comparing plant growth between biodegradable and
plastic container under nursery conditions or containers larger than 12.7 cm diameter, and the
exact water usage amount that plants need to grow relative to alternative container materials has
not been determined.

8

Woody Ornamental Irrigation Management
Introduction
In 2010, Michigan nursery and floriculture industry receipts totaled $621 M dollars and
accounted for 9.6% of the entire state’s agricultural receipts (National Agricultural Stastical
Service, 2011). Container nurseries require a large amount of irrigation to produce marketable
plants; however, water use is already limited by laws and regulations to varying degrees in
several states such as Florida, Delaware, California, North Carolina, Texas, Oregon, Maryland,
North Carolina and Michigan (Fernandez et al., 2009). Excessive irrigation not only wastes water
but can contaminate water resources with agrichemical runoff. In many agricultural areas,
groundwater contamination with nitrates has become a problem, with nitrate levels often
exceeding the Federal drinking water standard of 10 mg· -1 (Fare et al., 1994; Rathier and Frink,
L
1989). Due to increased competition for water resources and stricter environmental regulations,
irrigation usage by nursery will is likely to be further restricted and the industries will be need to
be more efficient in water use (Majsztrik et al. 2011; Nemali and van Iersel 2006).
This review will address the following topics related to container nursery irrigation and water
conservation strategies:
1. Container nursery irrigation overview
2. Current irrigation systems
Overhead irrigation
Micro irrigation
Subsurface irrigation
3. Irrigation efficiency
Cyclic schedule
9

Leaching fraction
Management allowed deficit irrigation
Precision irrigation based on evapotranspiration and plant water demand
4. Soil moisture content measurement methods
Time Domain Reflectometer
Capacitance sensors

Container Nursery Irrigation Overview
Container nurseries consumes large amounts of water to produce marketable plants. In the
southeastern U.S., nurseries generally use 1.8 to 2.9 meters of irrigation water yearly on a
relatively small land area, and are considered as high water users (Beeson, 2004). However,
water resources are becoming restricted or limited because of drought, competition and
legislation (Knox, 1989; Nemali and van Iersel 2006). For example, in some areas of Florida,
the amount of water allowed to be used by growers has dropped by 40% in 12 years and the
availability of groundwater to container nurseries is expected to drop significantly in the next
ten years (Beeson, 2004).
Excessive irrigation in agricultural operations can result in fertilizer and chemical runoff,
which can affect surrounding water resources and ecosystems (Cabrera, 2005; Hart et al., 2004;
Mitsch et al., 2001). Colangelo and Brand (2001) discovered that for containerized
rhododendrons, 51.8 and 60. 5 kg ha-1 nitrate was released in leachate for overhead and trickle
irrigation systems annually. Fare et al. (1994) reported that the nitrate loss through container
leachate could reach 63% when 13 mm irrigation was applied in one cycle. Wilson and Albano
(2011) found that the nitrate-N concentration in drainage water from container nurseries ranged
10

from 0.5 to 322.0 mg L-1 when using fertigation with urea and nitrate-based soluble
formulations. Additionally, Million et al. (2010) reported that for #1 (~3-Liter) sweet
viburnum, the loss of N, P and K increased 34, 38 and 45%, respectively by increasing the
irrigation rate from 1 to 2 cm· -1 under a fertilizer rate of 15 g 18N-2.6P-10K control release
day
fertilizer per container.
Several studies have demonstrated that reducing irrigation volume can reduce runoff volume
and nutrient loss. Tyler et al. (1996) reported that runoff volume could be reduced by 63% when
the cyclic irrigation volume was reduced by 44%. Additionally, the NO3, NH4 and P content in
the runoff decreased by 66%, 62% and 57%, respectively. Similarly, Owen et al. (2008)
performed an irrigation study on containerized Skogholm cotoneaster by decreasing leaching
fractions (LF; effluent/influent) from 0.2 to 0.1, finding that the cumulative container influent
and effluent volume was reduced by 25% and 64%, and also the P concentration and load in the
runoff was 6% and 64% less. Warsaw et al. (2009a) reported that when irrigation was based on
plant daily water use (DWU), the average runoff volume was up to 79% less compared to 19
mm irrigation application per day. The N and P load in the effluent was reduced by 59% and
74% under the most conservative irrigation treatment.
Successful irrigation practices in the container nursery should be able to conserve water and
reduce effluent and nutrient loss without compromising plant production quality. Gilman et al.
(2009) reported that for holly, pittosporum, and viburnum, there were only minor influences in
shrub growth when watered with two irrigation frequencies (2 or 4 days) and three irrigation
volumes (3, 6 or 9 liter per plant per event). Warsaw et al. (2009b) reported that woody
ornamentals under irrigation scheduling based on plant DWU had greater or equal growth
compared to plants under 19 mm irrigation per day. Those studies indicate that excessive
11

irrigation could negatively impact plant growth however proper irrigation could positively
influence plant performance. For container nursery growers to implement best management
practices (BMP), irrigation practices should be precise and based on plant actual water use
(Yeager et al., 1997). Yet limited research has been published on this.

Current irrigation systems
When determining irrigation systems, plant water requirements, water availability and
irrigation system design need to be considered (Majsztrik, 2011). The most common current
irrigation systems used by container nurseries include overhead and microirrigation.

Overhead irrigation
Overhead irrigation systems are the most common irrigation method in container nurseries in
the U.S. (Fare et al., 1994). They are widely used for container sizes less than 26.5 liter because
installing individual emitters on small containers is not considered economically feasible
(Bilderback, 2002; Garber et al., 2002). Beeson and Knox (1991) reported that the irrigation
efficiency of the overhead systems was 25% and 37% when the containers were spaced closely
and 7.6 cm apart. They also found 57% to 70% of the water was delivered to the substrate
surface by overhead irrigation depending on the crop, plant spacing and sprinkler type. In most
areas of Florida, overhead irrigation is restricted to nighttime watering with 0.8 to 1.5 cm of
water per application because of its low efficiency compared to other irrigation methods (Yeager
et al., 2010).
The main advantage of overhead irrigation systems is its flexibility for various container sizes
and numbers (Mathers et al., 2005). The overhead system layout configuration could be square,

12

triangular or rectangular patterns. The most efficient overhead irrigation system layout for most
nurseries is a square design with 90 degree emitters at the corners and 180 degree emitters along
the sides (Bilderback, 2002).

Micro Irrigation
Micro irrigation systems are often used for plants that are grown in containers larger than 15
liters (Beeson and Knox, 1991). These systems use drip emitters or spray stake nozzles to deliver
water directly into the containers; therefore, it is more efficient than overhead irrigation systems
(Bilderback, 2002). Lamm and Trooien (2003) reported that the efficiency of subsurface micro
irrigation can reach to 95% to 99% if the soil evaporation is carefully managed, which is much
higher than the efficiency of overhead irrigation mentioned above.
Since the emitters orifices of microirrigation systems are much smaller than overhead
sprinklers, the emitters can be clogged and need to be examined often. Microirrigation systems
require filters and water treatment may be needed to remove solids and ions that lead to clogging
of emitters (Bilderback, 2002).

Irrigation Efficiency
Irrigation efficiency (IE) is a parameter to evaluate the performance of irrigation water use
from a water conservation standpoint (Bos and Wolters, 1990). There are several definitions of
water use efficiency related to irrigation systems. Weatherspoon and Harrell (1980) defined
irrigation efficiency (IE) as the amount of water retained in the substrate compared to the
percentage of the total irrigation amount applied. Burt et al. (1997) expressed IE as a percentage
of the water amount plants used to the irrigation volume applied minus the amount changed in

13

the container storage. Howell (2003) evaluated irrigation efficiency by three factors: the
performance of the irrigation system, the irrigation uniformity, and plant response to irrigation.
He defined seasonal irrigation efficiency as the percentage of irrigation volume beneficially used
by the crop by the water amount delivered to the field. He also defined water use efficiency as
the percentage of crop dry matter by amount of water used.
Irrigation efficiency depends on many factors such as environmental conditions, system
performance, container spacing, and plant leaf morphology. Beeson and Knox (1991) concluded
that water shedding and possible water retention are the major causes for low irrigation
efficiency for container nurseries. Beeson and Yeager (2003) evaluated the IE of overhead
irrigation systems for viburnum, ligustrum, and azalea grown in 11.4 L containers spaced from 0
to 51 cm apart, finding that for all three species, the percentage of water captured increased as
the adjacent canopy interaction decreased. They suggested that maximum IE could be obtained
when containers are spaced at the minimum distance where the plant canopy was segregated.
Since water is a valuable resource with increasing demand, and excessive irrigation can result
in nutrient loss and water resource contamination, numerous attempts have been made to
increase irrigation efficiency and conserve water for container nurseries (Majsztrik et al, 2011).
The current solutions to increase irrigation efficiency include: cyclic irrigation, leaching fraction,
managed allowable deficit, and precision irrigation.

Cyclic Irrigation
Cyclic irrigation is defined as separating the daily irrigation volume into several applications
(Beeson and Haydu, 1995). This system includes one phase where the irrigation is active and one
phase where irrigation is off (Karmeli and Peri, 1974). Industry adoption of cyclic irrigation is

14

good, for example, west-central Florida nurseries use cyclic overhead systems 42% of the time
and cyclic microirrigation 47% of the time (Schoene et al., 2006). Fare et al. (1994) reported that
for Ilex crenata, when 13 mm irrigation water was applied in three cycles, the leachate volume
was 34% less compared to 13 mm irrigation applied in a single time. They also found that when
irrigation was delivered in one, two, or three cycles, the N leachate ratio to N applied was 63%,
56%, or 47% respectively. Karam and Niemiera (1994) reported that water application efficiency
was 4% greater when the irrigation was applied in cycles rather than continuously. Additionally,
they discovered that the water application efficiency increase as the interval between applications
increased from 20 to 60 min.
Research has shown that cyclic microirrigation systems increase water use efficiency, reduce
leachate nutrient loss and positively affect plant growth. Lamack and Niemiera (1993) found that
cyclic irrigation increases irrigation application efficiency by 24% compared to a single
application. Beeson and Haydu (1995) found that red maple, winged elm, live oak and crape
myrtle have increased growth under cyclic microirrigation compared to overhead irrigation in
single applications. Similarly, Fain et al. (1998) evaluated growth of Acer rubrum and leachate
nitrate loss under cyclic microirrigation with pot in pot production, finding that Acer rubrum
growth was greater with irrigation in six cycles than a single cycle. Additionally, they discovered
that nitrate loss decreased by 89% with cyclic microirrigation compared to a single application.
Warren and Bilderback (2002) investigated the cyclic irrigation timing effect on Cotoneaster
dammeri ‘Skogholm’ growth, finding that plants performed better with an afternoon cyclic
irrigation than morning applications.

15

Leaching Fractions
Leaching fraction (LF) is defined as the leachate volume collected from the container divided
by the total irrigation volume applied to the container (Ku and Hershey, 1992). Several studies
have been investigated the effects of irrigating to various LF on plant growth, soluble salt
accumulation and water usage.
Research has shown that low LF can reduce container nursery influent and effluent, but
increases soluble salt accumulation in container substrates. It has been demonstrated that plants
respond to low LF irrigation differently depending on their salt tolerance (Ku and Hershey, 1992;
Yelanich and Biernbaum, 1993). Tyler et al. (1996) evaluated the effect of two LF levels and two
fertilizer rates on IE, nutrient loss and growth of Cotoneaster dammeri Schneid, finding that low
LF of 0.0 to 0.2 reduced the irrigation and runoff volume by 44% and 63% compared to high LF
of 0.4 and 0.6, respectively. Additionally, NO3, NH4 and P load in the effluent was decreased by
66%, 62% and 57% under low LF, respectively. Similarly, Owen et al. (2008) reported that by
reducing LF from 0.2 to 0.1, the container influent and effluent volume was reduced 25% and
64%, respectively. Sammons (2008) found that near zero LF was 175% more water efficient than
the 0.2 LF regime.
Reduced LF generally increases the soluble salt accumulation in substrates, which might
damage plant growth (Sammons, 2008). Ku and Hershey (1992) found that geranium had a 26%
dry weight decrease with LFs of 0 and 0.1 comparing to LFs of 0.2 and 0.4; they also reported
that EC level increased to 6 dS· -1 in LF of 0.1 which may result in growth reductions.
m
However, greenhouse crops do not receive rainfall to help moderate soluble salt accumulation as
do nursery crops. Tyler et al. (1996) reported a 10% decrease in Cotoneaster dammeri Schneid
growth when irrigated at LF of 0.0 to 0.2 compared to LF of 0.4 to 0.6. In contrast, Graves et al.
16

(1995) discovered that the growth of woody legumes was not affected by LF of 0, 0.2 and 0.4
with fertilizer solution rates of 3.6 and 10.7 mol N· -3 for ten weeks.
m

Management Allowed Deficit Irrigation
Few nurseries monitor substrate moisture content or evapotranspiration in order to irrigate
according to plant need and increase irrigation efficiency. Several studies have been conducted to
investigate the effect of substrate moisture level on plant growth. This type of research usually
uses a pulsed irrigation system that maintains or initiates irrigation at certain substrate moisture
content, which is also refer to management allowed deficit (MAD) irrigation.
Several studies have been published associating the relationship between management
allowed deficit (MAD) irrigation level and plant growth. Welsh and Zajicek (1993) evaluated
growth and water use of container-grown Photinia x fraseri (Dress) with the substrate moisture
level maintained at 0, 5, 10, 25, 50, 75 and 95% deficit, finding optimal plant growth at 25%
MAD. Beeson (2006) reported that high MAD levels of 60% and 80% reduced woody
ornamental plant growth and increased production time; he also recommended MAD levels of
20%, 20%, 25% and 40% for optimal growth of Viburnum odoratissimum Ker Gawl, Ligustrum
japonicum Thumb, Photina xfraseri L., and Rhaphiolepis indica Lindl.

Precision Irrigation Based on Evapotranspiration and Plant Water Demand
Evapotranspiration (ET) of container plants refers to water loss both from substrate
evaporation and plant transpiration. It depends on solar radiation, temperature, plant canopy
architecture, container substrate, plant physiology and plant size (Bacci et al., 2008). Beeson and
Brooks (2006) reported that the same marketable size plants were obtained both under ET-based
17

system and irrigation regime that approximated annual 1800 mm· -1 overhead irrigation,
ha
however, they found that the production rate of an ET-based irrigation system was three weeks
faster with 400 mm· -1 less water used. Comparably, Million et al. (2010) compared a ETha
based irrigation schedule to a fixed rate irrigation in regards to water use, nutrient loss and plant
growth, finding that ET-based irrigation decreased irrigation influent and effluent by 39% and
42% without affecting the growth of viburnum. Moreover, they reported 16%, 25% and 22%
reduction in runoff of nitrogen, phosphorus and potassium compared to 10 mm· -1 rate
d
irrigation, respectively.
Crop Coefficient (Kc) is a ratio of the water use of a specific crop to that of a reference crop,
which is defined as the amount of ET from the surface of 8 to 15 cm tall green cover under solar
radiation with unlimited water resources (Doorenbos and Pruitt, 1975). There are several factors
that influence Kc such as container spacing, plant species, growth stage, and climate condition.
Burger et al. (1987) classified twenty-three woody ornamental container grown plants into high
water users, moderate water users and light water users by calculating the crop coefficient. They
also found that container spacing had an impact on Kc, because the wider the spacing the more
surface area of the container will be exposed to the sun, therefore increasing the
evapotranspiration and Kc. Schuch and Burger (1997) evaluated the crop coefficient of twelve
species of woody ornamentals grown in containers, finding that Kc was dependent on the season
and plant growth stages, they also reported that high water use plants have more fluctuations in
Kc during the growing season while Kc for low water use plant remains relatively stable. Niu et
al. (2006) determined the water use and Kc of five woody species that were grown in both
above-ground 10-L containers and 56-liter drainage lysimeters. They reported that the crop

18

coefficient was not different in two systems within same species; however, Kc fluctuated with
sampling days.

Soil Moisture Content Measurement Methods
Scheduling irrigation according to soil moisture level and plant needs can improve IE and
avoid excessive irrigation (Greenwood et al., 2010). Several measurement techniques have been
developed in order to precisely measure soil moisture content such as soil water balance
calculations, tensiometers, time domain reflectometer and capacitance sensors. The following
discussion focuses on time domain reflectometer and capacitance sensors.

Time Domain Reflectometer
Time Domain Reflectometer (TDR) has been utilized to measure soil moisture content and
bulk electrical conductivity since 1980. It measures the propagation time of an electromagnetic
signal as it moves through a soil or substrate, which depends on the soil dielectric properties as a
function of the water content surrounding the probes (Blonquist et al., 2005). TDR can respond
to soil water change quickly; however, it is expensive to install, the initial cost ranged from
$8,000 to 10,000 without dataloggers (Evett, 1999). Calculation curves of TDR and its utilization
in irrigation systems have been evaluated. Silva et al. (1998) determined the calibration curve for
TDR in several substrates including tuff, vermiculite, perlite and a mix of composted agricultural
waste and concluded that the TDR probe needs to be calibrated individually for specific
substrates.
Ristvey (2004) reported that irrigating containerized plants according to plant needs using
TDR sensors decreased nutrient loss and influent by 60% to 85% for a nursery over 9

19

months. Miralles-Crespo and van Iersel (2011) studied the performance of begonia under six soil
volumetric water content (SVWC) thresholds, measured by TDR, and found that the irrigation
system with TDR was able to maintain the SVWC within 0.008 m3· -3 of certain thresholds.
m
Additionally, they reported that TDR could be used for soilless substrates but it needs specific
calibration.

Capacitance Sensors
Capacitance sensors use the technology based capacitive coupling, it detects anything that is
conductive or has a dielectric value different from that of air.
Capacitance sensors are able to measure soil water content accurately but factors like soil type
and container size need to be considered. Kizito et al. (2008) evaluated capacitance sensors for
soil water content measurement under a range of soil types, finding that a single calibration curve
could fit all tested mineral soils, and the sensor measurement is accurate regardless of soil
salinity. Arguedas et al. (2006) evaluated the performance of capacitance sensors in peat and
gravel substrate with various container sizes, finding that the sensors were able to precisely
measure the water content in both substrates. Sensor location has a great effect on the moisture
content reading; when choosing and placing sensors, factors like substrate property, pot height
and size need to be considered. Also there should be adequate contact between the substrate and
sensor otherwise the reading will be affected by air gaps between the soil and the sensor
(Greenwood et al., 2010; van Iersel et al., 2009). Lea-Cox et al. (2008) integrated capacitance
sensors into a network that monitored real time information about environmental parameters and
substrate moisture conditions, indicating that growers could install a small 25-sensor network for

20

around $ 5,000, and this initial investment would be paid back by improved plant growth and
reduced nutrient runoff and water cost.
Warsaw et al. (2009b) evaluated irrigation based on plant daily water use and its impact on
woody ornamental plant growth and irrigation amount, finding that the growth of all tested
woody taxa was not affected by irrigation regime, and the irrigation amount applied was reduced
by 6% to 75% with plant daily water use based irrigation compared to fixed 19 mm· -1 daily
ha
irrigation. Fulcher et al. (2012) tested a demand-based system with substrate moisture set points
at 22, 30, 41, 49 m3· -3, reporting that the plants under 30, 41 and 49 m3· -3 used 1.4, 1.2 and
m
m
1.05 times more water than irrigation treatment with set point of 22 m3· -3. They demonstrated
m
that demand-based irrigation systems could reduce water influent of container nursery without
compromising plant production quality.

21

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22

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CHAPTER ONE
GROWTH AND WATER USE OF TEN WOODY ORNAMENTALS UNDER FOUR
IRRIGATION REGIMES

31

Abstract
Container-grown woody ornamentals were irrigated at four different levels based on daily
water use (DWU) to study the impact on plant growth, leachate electrical conductivity and pH,
and runoff water volume and nutrient content. A completely randomized design was used with
four overhead irrigation treatments: 1) irrigation scheduled to replace 100% DWU per
application (100DWU); 2) irrigation alternating every other application with 100% DWU and
75% DWU the following application (100-75); 3) irrigation scheduled on a three-application
cycle replacing 100% DWU followed by two applications replacing 75% DWU (100-75-75); 4)
irrigation scheduled on a four-application cycle replacing 100% DWU followed by three
applications replacing 75% DWU (100-75-75-75). The substrate volumetric moisture content (θ)
was determined by soil moisture sensors (Model 10 HS, Decagon Devices, Inc., Pullman, WA
99163) placed in a subset of containers. Plant DWU was calculated as the difference between θ 1
hour after irrigation and θ immediately before irrigation the following day. Irrigation was
scheduled by a programmed datalogger (CR3000, Campbell Scientific Inc., Logan, Utah 84321)
based on the highest DWU calculation from the sensors in each zone. Irrigation applications
were separated by at least 24 hrs. Irrigation treatments were applied to Hibiscus syriacus
‘Bricotts’, Euonymus alatus ‘Select’, Weigela florida ‘Alexandra’, Spiraea japonica ‘Yan’ in
10.2-L (#3) containers in 2011. The average daily irrigation amount applied for 100 DWU, 10075, 100-75-75, and 100-75-75-75 were 513, 424, 473, and 423mL, respectively. In 2012,
Viburnum dentatum ‘Ralph Senior’, Potentilla fruticosa ‘Lundy’, Thuja occidentalis ‘Sunkist’,
Juniperus horizontalis ‘Hegedus’, Hydrangea paniculata ‘Limelight’, Hypericum x ‘Cfflpc-1’ in
10.2 L containers were exposed to the irrigation treatments. The average daily irrigation amount
applied for 100DWU, 100-75, 100-75-75 and 100-75-75-75 were 900, 980, 970, and 910ml,

32

respectively, with little differences among treatments. There were no differences in final plant
growth, final electrical conductivity (EC) and pH, runoff NO3-, or PO43- concentration among
treatments for both years. The seasonal average NO3- and PO43- runoff loads were not different
between treatments in 2011; in 2012, the seasonal average daily PO43- runoff load of 100-75 was
the highest versus 100-75-75-75 which was the lowest compared to other treatments. NO3- load
was not different between treatments. The average runoff volume in 2011 and 2012 was 45,457
and 49,954 L·ha-1. These results indicate that irrigation could be applied based on plant DWU or
at a deficit without negatively affecting plant growth and also reducing water runoff volume.

33

Introduction
Container nurseries require intensive irrigation to produce marketable plants; however,
excessive irrigation in agricultural operations can result in large quantities of runoff carrying
fertilizers and other agrichemicals, which pose threats to surrounding water resources and
ecosystems (Cabrera, 2005; Hart et al., 2004; Mitsch et al., 2001). Nursery water use is already
limited by law and regulations in several states such as Florida, Delaware, California, North
Carolina, Texas, Oregon, Maryland, North Carolina and Michigan (Fernandez et al., 2009). For
example, in some areas of Florida, the water amount allowed to use by growers dropped by 40%
in 12 years and the availability of ground water to container nurseries is forecasted to drop
significantly in the next ten years (Beeson, 2004).
In order to improve water use efficiency and reduce runoff, many studies have investigated
irrigation practices that could conserve water and reduce runoff (Fulcher et al., 2012; Gilman et
al., 2009; Tyler et al., 1996: Warsaw et al., 2009a, 2009b). Tyler et al. (1996) reported that
runoff volume could be reduced by 63% when the cyclic irrigation volume was reduced by
44%. Additionally, the NO3-, NH4+ and P content in the runoff decreased by 66%, 62% and
57% respectively. Owen et al. (2008) performed an irrigation study on containerized Skogholm
cotoneaster, finding that by decreasing leaching fractions (LF; effluent/influent) from 0.2 to 0.1,
the cumulative container influent and effluent volume was reduced by 25% and 64%, and the P
concentration and content in the runoff was 6% and 64% less.
For container nursery growers to implement best management practices, the irrigation
practice should be precise and based on plant actual water use (Yeager et al., 2010). Warsaw et
al. (2009a) reported that woody ornamentals with irrigation scheduled based on plant DWU had
greater or equal growth compared to plants under 19 mm daily irrigation (control) even under
34

deficit treatments. Warsaw et al. (2009b) also reported that DWU-based irrigation reduced
average runoff volume by up to 79% compared to the control application.
Since the highest deficit irrigation treatment in Warsaw’s experiment, 1 day of 100% DWU
and 2 days of 75% DWU replacement, did not negatively affect plant growth, the objective of
this experiment is to: 1. further restrict the irrigation applications and investigate the impact on
plant growth, runoff and nutrient movement. 2. determine the DWU and water use efficiency of
several containerized woody ornamental shrubs.

Material and Methods
Site specifications
The experiment was performed on 12 nursery beds at Michigan State University
Horticulture Research and Teaching Center (HTRC) located in Holt, Michigan. A detailed
description of the nursery beds can be found in Warsaw et al., 2012. Natural precipitation was
not excluded in the experiment and was recorded by a Michigan Automated Weather Network
station (MAWN) located at the HTRC.

Experimental design
This was a one-factor completely randomized experiment with four irrigation treatments.
Each of the four irrigation treatment was triplicated and randomly assigned to twelve nursery
beds. Irrigation treatments were: 1) irrigation scheduled to replace 100% DWU per application
(100DWU); 2) irrigation alternating every other application with 100% replacement of DWU
and 75% DWU (100-75); 3) irrigation scheduled on a three-application cycle replacing 100%
DWU followed by two applications replacing 75% DWU (100-75-75); 4) irrigation scheduled on

35

a four-application cycle replacing 100% DWU followed by three applications replacing 75%
DWU (100-75-75-75).
In 2011, each nursery bed consisted of 32 plants with two replicates for each experimental
species. Plants of all species were randomly arranged in four rows of eight. In 2012, each
nursery bed consisted of 36 plants with six replicates for each species. Plants were randomly
arranged in six rows of six. Additionally, guard plants rows were placed surrounding the
replicates in 2011 and 2012. No data was collected from guard plants since they were designed to
minimize edge effects.

Plant material and culture
Plant species and cultivars used in 2011 and 2012 are shown in Table 1.1. The plants were
received from a commercial nursery in August of the years preceding the experimental periods
and transplanted into 10.2-L (#3) containers. In 2011, plant material was transplanted from 5.7cm potted liners on Sep 17, 2010. Container substrate consisted of 85% pine bark: 15% peatmoss (vol: vol). Plants were fertilized on 5 July 2011 using 54 gram 17.0N-3.5P-6.6K control
release fertilizer including micronutrients with a release period of 4 months at 27℃ (HFI
Topdress Special; Harrell’s Inc., Lakeland, FL). In 2012, plants were transplanted from 5.7-cm
potted liners on Sep 6, 2011 into the same substrate blend. Plants received the same fertilizer
application as in 2011 on Aug 16, 2012.

36

Table 1.1. Container-grown woody ornamentals grown in the 2011 and 2012 irrigation
experiments
2011
Hibiscus syriacus ‘ Bricotts’
Euonymus alatus ‘Select’
Weigela florida ‘Alexandra’
Spiraea japonica ‘Yan’
2012
Viburnum dentatum ‘Ralph Senior’
Juniperus horizontalis ‘Hegedus’
Potentilla fruticosa ‘Lundy’
Hydrangea paniculata ‘Limelight’
Thuja occidentalis ‘Sunkist’
Hypericum x ‘Cfflpc-1’

Irrigation treatment application
The irrigation system was an overhead system controlled by solenoid valves through a
programmed datalogger. Distribution uniformity of each bed (replicate) was determined to be 0.8
or greater during a period without wind according to Fernandez (2010). The irrigation volume
applied was based on the highest DWU measurement for each replicate to avoid under-watering
any species and assuming that the irrigation water penetrates the canopy at 100%. The irrigation
was initiated at 0700 HR each day starting from replicate one. In 2011, irrigation applications
were applied from 23 June through 2 Nov. In 2012, irrigation was applied daily from 26 June to
13 Oct.

37

Daily water use
The soil volumetric moisture content (θ) was measured with soil moisture capacitance
sensors (Model 10HS, Decagon Devices Inc., Pullman, WA, USA). For each taxon, one plant
container from each bed was randomly selected to insert one sensor. The sensors were inserted at
the northeast side, centered between the plants and the container edge at a 45° angle. The sensor
readings were recorded by a datalogger (Model CR3000, Campbell Scientific Inc., Logan, UT,
USA) every 15 min. The container capacity was determined to be 53.4% by measuring θ after
irrigating to saturation and gravitational drainage. The DWU was determined by the equation:
DWU= (θAI-θBI) x container volume, where θAI was measured one hour after irrigation and θBI
was measured right before the next irrigation application. The datalogger was programmed to run
the irrigation system through relays and solenoid valves to replace the DWU per nursery bed
according to specific treatments described above.

Plant growth
Plant growth measurements were taken approximately every two weeks. Plant height was
taken from the rim of the container to the highest point of the plant; width1 was the width of the
plant from north to south direction and width 2 was the width of the plant from west to east
direction. Plant growth index (GI) was calculated as GI= (height+width1+width2)/3. The GI
increment was defined as the final GI value minus the initial GI value.

Leachate electrical conductivity and pH
Electrical conductivity（EC）and pH measurements of leachate water from individual
containers were taken every month during the treatment periods. Two replicate plants per bed for
38

each taxon were randomly selected at the first measurement and repeatedly measured afterwards.
Thirty minutes after irrigation was applied a tray was placed under the container, then 200 ml pH
neutral reverse osmosis water was added to the container to force out leachate. A bulb syringe
was used to extract leachate from the tray and apply it to the sensors of Cardy Twin EC Meter
and Cardy Twin PH Meter (Spectrum Technologies, Inc., Illinois) to determine leachate EC and
pH.

Water use efficiency (WUE) and crop coefficient (Kc):
In order to further investigate the plant response to irrigation volume, WUE and Kc was
calculated. WUE was defined by two calculations in this chapter, it was calculated as the
increment in growth index divided by plant DWU under 100DWU treatment and it was also
calculated as growth index increment divided by water amount applied under four irrigation
treatments. Kc was defined as plant DWU under 100DWU treatment divided by reference
potential evapotranspiration (RPET).

Runoff water collection:
Runoff water was collected every month at the beginning of each irrigation cycle, which was
when all the irrigation treatments for the 12 beds were at the 100DWU application cycle. The
basins for capturing runoff were cleaned by vacuum on the day prior to the collection days. The
runoff was collected on four consecutive days in order to collect runoff for one complete cycle of
the 4 treatments. The runoff from the basin was pumped into a calibrated collection container in
order to determine the volume. Runoff volume was converted to liter per hectare by multiplying
the ratio between production area and hectare area. Two 20 ml bottles were used to take water

39

samples for each bed. The water samples were filtered through Watson 504 filter paper and then
transfer into 15 ml corning tubes. The filtered samples were shipped to USDA Horticulture
Research Laboratory (Fort Pierce, FL) to analyze for phosphorus, nitrogen and micronutrients
concentrations. The nutrient concentration result was obtained as mg per liter and then
converted to nutrient load by multiplying by the runoff volume.

Statistical analysis:
GI, leachate EC and pH were analyzed as repeated measurements using the PROC MIX
procedure of Statistical Analysis Software (SAS Version 9.2; SAS institute, Cary, NC). When
treatment effects were significant at p ≤ 0.05 level, treatment means were separated using t-test
in the PDIFF option of the LSMEANS statement and the SLICING option of PROC MIXED
(α=0.05). WUE, DWU, total volume of water applied, runoff volume and nutrient loss were
analyzed using PROC GLM with Tukey’s adjustment.

Results and Discussion
Water applied 2011 and 2012
In 2011, there was 133 irrigation applications. When precipitation occurred, θBI value
occasionally was greater than θAI resulting in a negative DWU; the program was set to not
irrigate when DWU was negative. Irrigation applied of four treatments gradually increased
during the first half of the experiment before gradually declining during the second half (Figure
1.1 A-D). Daily irrigation applied under 100DWU treatment was generally greater than 100-75,
100-75-75 and 100-75-75-75 treatment. Irrigation amount of most treatments peaked on day 80,
81 and 82 (Sep 11-Sep 13, 2011). The daily irrigation amount fluctuation might be caused by
40

fluctuation of the RPET (Figure 1.3). The coefficient variation of 100DWU, 100-75, 100-75-75
and 100-75-75-75 was 0.47, 0.49, 0.58 and 0.62, respectively. The coefficient variation increased
from 0.49 to 0.58 when the irrigation treatment changed from 100-75 to 100-75-75, meaning
daily irrigation amount fluctuated more under 100-75-75 and 100-75-75-75 treatment, which is
also shown on Figure 1.1. The seasonal average daily water applied per container for 100DWU,
100-75, 100-75-75 and 100-75-75-75 treatments was 0.51, 0.42, 0.47, 0.42 L, respectively
(Table1.2). The water applied for 100DWU was the greatest among all treatments; the water
applied for 100-75 and 100-75-75-75 was the least. Although the seasonal mean of water applied
of 100-75 and 100-75-75-75 treatment was similar, 100-75 treatment provide a more stable daily
irrigation amount compare to 100-75-75-75.
In 2012, there was 109 irrigation applications. Water applied of four treatment generally
peaked during the first quarter of the experiment before gradually declining during the rest
period (Figure 1.2 A-D). The peak daily irrigation amount under most irrigation treatment
appeared from day 6 to day 20 (July 2-July 16, 2012). The daily irrigation amount fluctuation
might be caused by fluctuation of RPET in 2012 (Figure 1.3). The coefficient variation within
treatment 100DWU, 100-75, 100-75-75 and 100-75-75-75 was 0.33, 0.32, 0.32 and 0.33,
respectively. The coefficient variation within each treatment was similar, which means the daily
irrigation amount fluctuate similarly under four treatments. However, comparing to 2011, the
irrigation amount applied per container for 100DWU, 100-75, 100-75-75, and 100-75-75-75 was
76.5%, 133.3%, 106.4% and 116.7% greater than in 2011, respectively. This may be due to
larger plants and higher RPET rate in 2012 (Figure 1.3). The seasonal average daily water
applied per container for the four treatments was 0.94 L with no differences between treatments.
Fare et al. (1994) found that nursery growers generally irrigate for 1 hour during growing season

41

assuming that 254,000 L· -1 water is applied daily, which is generally much more than our
ha
averaged 122,000 L· -1 experimental application rates. Warsaw et al. (2009b) evaluated similar
ha
irrigation treatments based plant DWU and its impact to on woody ornamental plant growth and
irrigation amounts, finding that the growth of all tested woody taxa was not affected by irrigation
regime, and the irrigation amount applied was reduced by 6% to 75% depending on taxa
compared to a fixed 190,000 L · -1 irrigation rate.
ha

Table 1.2. Daily water applied averaged over the season and seasonal total water applied from
23 June through 2 Nov. 2011 (133 d) for all plants. Plants were grown in 10.2-L containers under
four irrigation treatments.
Avg water applied per
Total seasonal water applied
Treatmentz
y
per container (L)
container per application (L)
100DWU
68.2a
0.51ax
56.3b
0.42b
62.9ab
0.47ab
56.2b
0.42b
z
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h.
y
Means separation using Tukey’s test (𝛼 =0.05), n=133.
100-75
100-75-75
100-75-75-75

x

Means with same letters are not significantly different (∝= 0.05)

42

L/ha x10000

15

A) 100DWU

10
5
0

L/ha x 10000

15

B) 100-75

10
5
0

L/ha x 10000

15
C) 100-75-75

10
5
0

L/ha x 10000

15
D) 100-75-75-75
10
5
0
0

10

20

30

40

50
60
70
80
90 100 110 120 130
Day of Experiment
Figure 1.1 A-D. Daily irrigation volume applied to containerized woody ornamental plants under
four irrigation treatments showing seasonal patterns from 23 June (Day 0) to 2 Nov, 2011.
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h.

43

L/ha x 10000

30
A)100DWU
20
10
0

L/ha x 10000

30
B)100-75
20
10
0

L/ha x 10000

30
C)100-75-75
20
10

L/ ha x 10000

0
30
D)100-75-75-75

20
10
0
0

10

20

30

40
50
60
70
Day of Experiment

80

90

100

Figure 1.2 A-D. Daily irrigation volume applied to containerized woody ornamental plants under
four irrigation treatments showing seasonal patterns from 26 June (Day 0) to 13 Oct, 2012.
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h
44

8
2011

7

2012

hr
RPET(mm· -1)

6
5
4
3
2
1
0
0

10

20

30

40

50
60
70
80
Day of Experiment

90

100

110

120

130

Figure 1.3. Referential potential evapotranspiration rate (RPET) of 2011 and 2012 from 23 June
to 2 Nov, 2011 and 2012. Data recorded at an Enviro-weather weather station located at the
Michigan State University Horticulture Teaching and Research Center

45

Growth index (GI)
In 2011, the final GI for H. syriacus ‘Bricotts’, E. alatus ‘Select’, W. florida ‘Alexandra’
and S. japonica ‘Yan’ was 41.03, 20.05, 55.28 and 31.31 cm, respectively, with no difference
between treatments. In 2012, the final GI of V. dentatum‘Ralph senior’, J. horizontalis ‘Hegedus’
P. fruiticosa ‘Lundy’, H. paniculata ‘Limelight’ T. occidentalis‘Sunkist’ and H. x ‘Cfflpc-1’ was
33.88, 24.44, 38.27, 51.92, 24.06 and 35.74 cm, respectively, also with no differences between
treatments.
Other studies have also reported that substantial reductions in irrigation did not negatively
affect plant growth. Welsh et al. (1991) irrigated Photina x fraseri plants at 100%, 75% and 50%
replacement of water use during the summer season (49 days), finding that the shoot extension,
shoot dry weight, leaf number and leaf area of the plant was not affected by the treatments. In
Warsaw et al. (2009a,b), three of the irrigation treatments were the same as in the current study,
100DWU, 100-75, and 100-75-75, and the GI of the woody ornamental shrubs was similar for
the three treatments.

WUE
In 2011, the WUE expressed as GI increment divided by DWU under 100DWU of H. syriacus
‘Bricotts’, W. florida ‘Alexandra’ and S. japonica ‘Yan’ was 0.57 with no difference between
taxa. The WUE of E. alatus ‘Select’ was excluded from the table because of its negative growth
increment which might have been caused by overwatering since the DWU of E. alatus ‘Select’
was the least among four species. For H. syriacus ‘Bricotts’ and S. japonica ‘Yan’, there were
no differences in WUE between treatments. For W. florida ‘Alexandra’, the WUE under 100-75

46

was greater than that of 100DWU. Seasonal mean WUE of W. florida ‘Alexandra’ was greater
than that of H. syriacus ‘Bricotts’ which was greater than S. japonica ‘Yan’ under all treatments.

Table 1.3. Estimated water use efficiency (WUE) and GI increment of three container-grown
woody ornamentals under four irrigation regimes from June 21 to Sep 27, 2011z
taxa
total water appliedx
Hibiscus syriacus
Bricotts
increased in GI (cm)
WUE
Weigela florida
Alexandra
increased in GI (cm)
WUE
Spiraea japonica Yan
increased in GI (cm)
WUE

100DWU

treatmenty
100-75
100-75-75

100-75-75-75

68.2

56.3

62.9

56.2

25.39
0.37avBw

21.30

19.75

24.72

0.39aB

0.31aB

0.45aB

35.57
0.52bA

38.91
0.69aA

35.89
0.57abA

37.00
0.66abA

17.07
0.25aC

15.61
0.28aC

15.86
0.25aC

17.51
0.31aC

z

WUE estimated as increase in growth index (cm) per liter of water per container

y

100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU; 100-75-75
= irrigation scheduled on a three-application cycle replacing 100% DWU followed by two
applications replacing 75% DWU; 100-75-75-75 = irrigation scheduled on a four-application
cycle replacing 100% DWU followed by three application replacing 75% DWU. DWU volume
applied based on the highest DWU of the four species on each measurement day. Irrigation
applications separated by at least 24h.
x
Liters per container from 21 June to 27 Sep. 2011
v

Means with same lowercase letters within the same row are not significantly different.

w

Means with same uppercase letters within the same column are not significantly different.
Means separation with Tukey’s test(𝛼 =0.05)
GI= growth index

47

In 2012, the WUE expressed as GI increment divided by DWU under 100DWU of V.
dentatum ‘Ralph Senior’, Juniperus horizontali ‘Hegedus’, P. fruticosa ‘Lundy’, T. occidentalis
‘Sunkist’, H. x ‘Cfflpc-1’ and H. paniculata ‘Limelight’ was 0.045, 0.027, 0.046, 0.083 and
0.270 respectively. H. paniculata ‘Limelight’ had the greatest WUE among the taxa studied. The
WUE of J. horizontalis ‘Hegedus’ was excluded from table because of negative growth
increment, which may have been caused by overwatering. The WUE of H. paniculata
‘Limelight’ was greater than of other taxa under all treatments. The WUE under 100-75, 100-7575 and 100-75-75-75 treatments was greater than that of 100DWU, and the lack of difference in
GI between DWU treatments could be due to drought adaptation with improved WUE. DeLucia
and Heckathorn (1989) also documented increased WUE of Pinus ponderosa Laws caused by
repeated drought cycles; they also reported that the primary factor contributing to higher WUE
was stomata closure which reduced transpiration.

48

Table 1.4. WUE and GI increment of five container-grown woody ornamentals under four
irrigation regimes from June 26 to Oct 11, 2012z
taxa
total water appliedx
V. dentatum Ralph Senior
increased in GI (cm)
WUE
P. fruticosa Lundy,
increased in GI (cm)
WUE
H. paniculata Limelight
increased in GI (cm)
WUE
T. occidentalis sunkist
increased in GI(cm)
WUE
Hypericum x Cfflpc-1
increased in GI(cm)
WUE

100DWU

100-75

treatmenty
100-75-75

99.1

107.5

106.2

99.8

3.167
0.032bv

3.833

4.574

2.870

0.036b

0.043b

0.029b

1.315
0.013b

1.500
0.014b

2.922
0.028b

4.188
0.042b

15.185
0.153a

15.185
0.141a

17.481
0.165a

19.833
0.199a

1.537
0.016b

1.778
0.017b

4.000
0.038b

0.630
0.006b

6.259
0.063b

3.593
0.033b

3.407
0.032b

3.037
0.030b

100-75-75-75

z

WUE estimated as increase in growth index (cm) per liter of water per container

y

100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h.
x
Liters per container from 26June to 11 Oct. 2012
v

Means with the same letters within the same column are not significantly different. Means
separation with Tukey’s test (𝛼 =0.05).
GI= growth index

DWU
In 2011, plants responded differently to irrigation treatments within each taxon (Figure 1.4).
The seasonal average DWU of H. syriacus‘ Bricotts’ under 100DWU and 100-75-75-75 was

49

higher than that of 100-75-75. For E. alatus ‘Select’, the DWU under 100DWU was lower than
other treatments. For W. florida ‘Alexandra’, DWU under 100-75-75 was higher than 100-75.
For S. japonica ‘Yan’, DWU under 100DWU and 100-75-75-75 was higher than 100-75.
In 2012, the seasonal mean DWU of H. paniculata ‘Limelight’ was greater than that of V.
dentatum ‘Ralph Senior’. The seasonal average DWU of V. dentatum ‘Ralph Senior’ was highest
under treatment 100-75, followed by 100-75-75, 100DWU and 100-75-75-75 had the lowest
DWU (Figure 1.5). For J. horizontalis ‘Hegedus’, DWU under 100-75-75 and 100-75-75-75 was
greater than that of 100-75. For P. fruticosa ‘Lundy’, DWU under 100-75 was the highest
compared to other treatments. For T. occidentalis ‘Sunkist’, DWU under 100-75 and 100-75-7575 was larger than that of 100DWU and 100-75-75. For H. paniculata ‘Limelight’, DWU under
100-75-75-75 was the highest while 100DWU had the least. For H. x‘Cfflpc-1’, DWU under
100-75-75 -75 was greater than 100DWU and 100-75.
Plant DWU ranged from 4,120 to 200,000 L ha-1 and was higher during the summer and
lower in fall (Figure. 1.6, Figure 1.7), reflecting variation in RPET. Kc was calculated as plant
DWU under 100DWU treatment divided by RPET and can be found in Table 1.5. Schuch and
Burger (1997) estimated Kc values of 12 woody ornamentals according to a 20 month study at
two California locations. They recommended using Kc to schedule irrigation only for low water
use plants since the Kc of high water users varied by location, microclimate and plant growth
stage. Burger et al. (1987) reported that Kc of container nursery plants varied by species and
container spacing, since as the container spacing increase more sunlight caused increased
temperature of the black nursery containers and thus increase the evapotranspiration. Due to
these complications, using Kc to scheduling irrigation in container nurseries is uncommon.

50

Daily Water use (mL)

600
500

100%
ax

100-75-75

400
300

100-75

bc c

100-75-75-75

ab

a
b

a

a

ab
b

a

ab
a

ab

a

b
200
100
0
H.syriacus.'Bricotts' E.alatus.'Select'

W.florida.'Alexandra' S.japonica.'Yan'

Plant taxa

Figure 1.4. Daily water use (DWU) from 23 June through 2 Nov. 2011 (133 d) for Hibiscus
syriacus ‘Bricotts’, Euonymus alatus ‘Select’, Weigela florida ‘Alexandra’, Spiraea japonica
‘Yan’ grown in 10.2-L containers under four irrigation treatments.
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h.
x
Means for each taxa with the same letters are not significantly different from each other. Mean
separated by t-test (p=0.05). n =18.
Error bars represent standard error of means from 18 plants of each species.

51

1200
100DWU
100-75
100-75-75
100-75-75-75

Daily water use (mL)

1000

a
b

800

a
a a

b

600
cx

c

ab

a

a

b

b

b

b

ab

b
c

b

a

a

b
b

400

b

200
0

Plant Taxa

Figure 1.5. Daily water use (DWU) of Viburnum dentatum ‘Ralph Senior’, Juniperus
horizontalis ’Hegedus’, Potentilla fruticosa ‘Lundy’, Hydrangea paniculata ‘Limelight’, Thuja
occidentalis ‘Sunkist’, Hypericum x ‘Cfflpc-1’ grown in 10.2-L containers under four irrigation
treatments from June 26, 2012 to October 13, 2012.
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h.
x
Means for each taxa with the same letters are not significantly different from each other.
Mean separated by t-test (p=0.05). n =18. Error bars represent standard error of means from 18
plants of each species
.

52

30

DWU
RPET

L/ha x 10000

A) H. syriacus ‘Bricotts’
20
10
0

-10
30

L/ha x10000

B) E. alatus ‘Select’
20
10
0

-10

L/ha x 10000

30
20

C) W. florida ‘Alexandra’

10
0

-10

L/ ha x 10000

30
20

D) S. japonica ‘Yan’

10
0

-10
0

10

20

30

40

50
60
70
80
90 100 110 120 130
Day of Experiment
Figure 1.6 A-D. Daily water use (DWU) from June 23, 2011 to Nov 2, 2011 for Hibiscus
syriacus ‘Bricotts’, Euonymus alatus ‘Select’, Weigela florida ‘Alexandra’, Spiraea japonica
‘Yan’ grown in 10.2-L containers under 100DWU irrigation treatment.

53

L/ ha x 10000
L/ ha x 10000
L/ ha x 10000

50
40
30
20
10
0
-10
-20
50
40
30
20
10
0
-10
-20
50
40
30
20
10
0
-10
-20

A) V. dentatum 'Ralph senior'

DWU
RPET

B) J. horizontalis 'Hegedus'

C) P. fruiticosa 'Lundy'
0

10

20

30

40

50
60
70
Day of Experiment

80

90

100

Figure 1.7 A-F. Daily water use (DWU) of Viburnum dentatum ‘Ralph Senior’, Juniperus
horizontalis ’Hegedus’, Potentilla fruticosa ‘Lundy’, Hydrangea paniculata ‘Limelight’, Thuja
occidentalis ‘Sunkist’, Hypericum x ‘Cfflpc-1’ grown in 10.2-L containers under 100DWU
irrigation treatment and PET from 26 June to 13 Oct, 2012

54

L/ ha x 10000

L/ ha x 10000

Figure 1.7. (cont’ d)
50
40
30
20
10
0
-10
-20
50
40
30
20
10
0
-10
-20

D) T.occidentalis 'Sunkist'

E) H. paniculata 'Limelight'

50

L/ ha x 10000

40
30

20
10
0
-10
-20

F) H. x 'Cfflpc-1'
0

10

20

30

40

50
60
70
Day of Experiment

55

80

90

100

Table 1.5. Crop Coefficient (Kc) of ten woody ornamental taxa from June to October in 2011
and 2012
Taxa
Kc
2011
Hibiscus syriacus ‘Bricotts’

1.91

Euonymus alatus ‘Select’

1.04

Weigela florida ‘ Alexandra’

2.50

Spiraea japonica ‘Yan’

1.61

2012
Viburnum dentatum ‘Ralph Senior’

1.62

Juniperus horizontalis ‘Hegedus’

2.31

Potentilla fruticosa ‘Lundy’

2.52

Hydrangea paniculata ‘Limelight’

1.69

Thuja occidentalis ‘Sunkist’

2.88

Hypericum x ‘Cfflpc-1’

3.47

56

Leachate EC
In 2011, leachate EC was similar among all taxa except for H.syriacus ‘Bricotts’ on day 19
where the leachate EC under 100DWU, 100-75, 100-75-75 and 100-75-75-75 was 1.19, 1.08,
1.26, and 1.48 dS· -1, respectively; with EC under 100-75-75-75 greater than that of 100-75.
m
The seasonal mean leachate EC of E. atalus ‘Select’, W. florida ‘Alexandra’ and S. japonica
‘Yan’ was 0.86, 0.88 and 1.01 dS· -1 , respectively.
m
In 2012, differences in leachate EC between treatments was observed only on day 6 and 100
and only for T. occidentalis ‘Sunkist’. On day 6, the leachate EC of T. occidentalis ‘Sunkist’
under 100DWU, 100-75, 100-75-75 and 100-75-75-75 was 0.82, 0.47, 0.58 and 0.77 dS· -1,
m
respectively; EC under 100DWU was greater than that of 100-75 and 100-75-75. On day 100,
the mean leachate EC of T. occidentalis ‘Sunkist’ under 100DWU, 100-75, 100-75-75 and 10075-75-75 was 1.15, 0.91, 0.88 and 1.43, respectively; EC under 100-75-75-75 was greater than
that of 100-75 and 100-75-75. The seasonal mean leachate EC of V. dentatum ‘Ralph Senior’, J.
horizontalis’ Hegedus’, P. fruticosa ‘ Lundy’ , H.paniculata ‘Limelight’, H. x ‘Cfflpc-1’ was
0.96, 1.02, 0.99, 1.06 and 1.08 dS· -1 , respectively.
m

Leachate pH
In 2011, leachate pH difference between treatments was only observed on day 19 for W.
florida ‘Alexandra’ and day 132 for H. syriacus ‘Bricotts’. On day 19, the mean leachate pH of
W. florida ‘Alexandra’ under 100DWU, 100-75, 100-75-75 and 100-75-75-75 was 7.13, 7.21,
6.82 and 7.06, respectively; pH under 100-75 was greater than that of 100-75-75. On day 132,
the mean leachate pH of H. syriacus ‘Bricotts’ under 100DWU, 100-75, 100-75-75 and 100-7557

75-75 was 7.65, 7.07, 7.88 and 7.64, respectively; the mean pH under 100-75-75 was greater
than that of 100-75. The seasonal mean leachate pH of E. atalus ‘select’ and S. japonica ‘Yan’
was 7.42 and 7.40.
In 2012, on day 41, 72 and 100, leachate pH of several of the deficit irrigation treatments
was greater than 100DWU for some taxa (Figure 1.8). On day 41, the leachate pH of H. x ‘Cfflp1’ under 100-75-75-75 was greater than that of 100DWU. On day 72, the leachate pH of P.
fruiticosa ‘Lundy’ under 100-75 was greater than that of 100DWU. On day 100, the leachate pH
of V. dentatum ‘Ralph senior’ under 100-75, 100-75-75 and 100-75-75-75 was greater than that
of 100DWU. The seasonal mean leachate of J. horizontalis ‘Hegedus’, T. occidentalis ‘Sunkist’
and H. paniculata ‘Limelight’ was 7.68, 7.65 and 7.79.

58

Figure 1.8 A-F. Leachate pH for Viburnum dentatum ‘Ralph Senior’, Juniperus
horizontalis ’Hegedus’, Potentilla fruticosa ‘Lundy’, Hydrangea paniculata ‘Limelight’, Thuja
occidentalis ‘Sunkist’, Hypericum x ‘Cfflpc-1’ grown in 10.2-L containers under four irrigation
treatments on experimental day 6, 41, 72 and 100.
100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three-application cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h. Means within taxa with the
same letters are not significantly different between treatments. Mean separated by tukey’s t-test
(α=0.05). n =18. ns = no significance

59

Nutrient loss and runoff
In 2011 and 2012, there was no difference in water runoff volume, runoff NO3- -N, PO43- -P
load and concentration between treatments. In 2011, the seasonal mean runoff volume was
45,457 L· -1d-1, the seasonal mean runoff PO43- -P and NO3--N load was 37 and 655 g·ha-1,
ha
and the seasonal mean runoff PO43- -P and NO3- -N concentration was 0.83 and 14.13 mg· -1.
L
In 2012, the seasonal mean runoff volume was 49,954 L· -1d-1, the seasonal mean runoff
ha
PO43- -P and NO3--N concentration was 1.17 and 29.12 mg· -1, and the seasonal mean runoff
L
PO43- -P and NO3- -N load is shown in Table 1.6; runoff PO43- -P load under 100-75 was greater
than that of 100-75-75-75.
Warsaw et al. (2009b) used the same research site and experimental design as the current
experiment to evaluate irrigation treatment effects on runoff volume. In Warsaw’s research, a
daily 19 mm control irrigation rate was use and had a seasonal mean runoff volume of 114,000
L· -1d-1, which is over twice the seasonal runoff volume in current study. Since the seasonal
ha
average runoff volume of DWU irrigation treatments was much less than that of this common
nursery rate both in the current study and Warsaw et al. (2009b) study, this demonstrates that the
runoff volume leaving the nursery can be reduced by scheduling irrigation based on plant DWU.
The seasonal mean NO− -N concentration in the current study exceeded 10 mg· -1 maximum
L
3
drinking water contamination level established by U.S. Environmental Protection Agency (U.S.
Environmental protection Agency, 2003). However, Warsaw et al. (2009a) reported that when
irrigation was based on plant DWU, the N and P loss in the effluent was reduced by 59% and

60

74% under the most conservative irrigation treatment and it was also below 10 mg· -1. This
L
difference may be caused by the different fertilizing ratio used in the different studies.

Table 1.6. Average seasonal runoff PO43- -P and NO3- –N load under four irrigation treatments.
Treatmentz

PO43- -P Load (g· -1)
ha

NO3- –N Load (g· -1)
ha

100DWU
100-75
100-75-75
100-75-75-75

68abx
88a
60ab
56b

1485a
1308a
1110a
1090a

z

100DWU = irrigation scheduled to replace 100% DWU per application; 100-75 = irrigation
alternating every other application with 100% replacement of DWU and 75% DWU the
following application; 100-75-75 = irrigation scheduled on a three applications cycle replacing
100% DWU followed by two applications replacing 75% DWU; 100-75-75-75 = irrigation
scheduled on a four-application cycle replacing 100% DWU followed by three application
replacing 75% DWU. Irrigation volume applied = highest DWU of the four species on each
measurement day. Irrigation applications separated by at least 24h.
x
Means with same letters are not significantly different (α=0.05)

61

Conclusions
Scheduling irrigation based on DWU did not negatively impact plant growth from June to
October during 2011 and 2012 even when using deficit irrigation applications. When compared
to the 19 mm· -1d-1 treatment in Warsaw et al. (2009a,b), the water applied and runoff volume
ha
was much lower in current experiment. These results indicate that nursery growers could
substantially reduce irrigation effluent without affecting plant growth while reducing runoff
volume and nutrient loss.
The pour through EC value of the substrate was generally above the recommended range of
0.2 to 0.5 dS· -1 for container grown woody ornamentals in pine bark substrate fertilized with
m
only a CRF (Southern Nursery Association, 2007). However, we did not notice any apparent
damage from soluble salts at these levels nor did previous studies (Warsaw et al., 2009a, b).
DWU, WUE and Kc of ten woody ornamental plants were identified. This information will
allow growers to group species with similar water use together in irrigation zones to conserve
water. Additionally, the method used in this experiment can be applied to identify the DWU and
Kc of more woody ornamentals in the future. In order to improve water conservation and
minimize environmental impact, growers could water crops based on DWU and group plants by
similar water use.

62

LITERATURE CITED

63

LITERATURE CITED

Beeson, R. C. 2004. Modeling actual evapotranspiration of Ligustrum japonicum from rooted
cuttings to commercially marketable plants in 12 liter black polyethylene containers.
In IV International Symposium on Irrigation of Horticultural Crops. 664: 71-77.
Burger, D., J. Hartin, D. Hodel, T. Lukaszewski, S. Tjosvold and S. Wagner. 1987. Water use in
California's ornamental nurseries. Calif Agr, 41(9): 7-8.
Cabrera, R. I. 2005. Challenges and advances in water and nutrient management in nursery and
greenhouse crops. Agr.Mediterr. 135:147-160.
DeLucia, E. H. and S. A. Heckathorn. 1989. The effect of soil drought on water‐use efficiency in
a contrasting Great Basin desert and Sierran montane species. Plant Cell Environ. 12(9):
935-940.
Fare, D. C., C. H. Gilliam and J. G. Keever. 1994. Cyclic irrigation reduces container leachate
nitrate-nitrogen concentration. HortScience. 29(12): 1514–1517.
Fernandez, R. T. 2010. Determining irrigation distribution uniformity and efficiency for
nurseries. National Proceedings: Forest and Conservation Nursery Associations-2009.
Proc. RMRS.
Fernandez, R. T., J. Lea-Cox, G. Zinati, C. Hong, R. Cabrera, Merhaut, J. Albano, M. van Iersel,
T.H. Yeager, and D.Buhler. 2009. NCDC216: A new multistate group for water
management and quality for ornamental crop production and health. J. Environ. Qual, 27:
814-820.
Fulcher, A. F., J. W. Buxton and R. L. Geneve. 2012. Developing a physiological-based, ondemand irrigation system for container production. Sci. Hortic. 138: 221-226.
Gilman, E. F., C. L. Wiese, M. Paz, A. L. Shober, S. M. Scheiber, K. A. Moore and M. Brennan.
2009. Effects of irrigation volume and frequency on shrub establishment in Florida. J
Environ Hortic. 27(3): 149.
Hart, M. R., B. F. Quin and M. Nguyen, 2004. Phosphorus runoff from agricultural land and
direct fertilizer effects. J. Environ. Qual. 33(6): 1954-1972.
Mitsch, W. J., Jr. J. W. Day, J. W. Gilliam, P. M. Groffman, D. L. Hey, G. W. Randall and N.
Wang. 2001. Reducing nitrogen loading to the Gulf of Mexico from the Mississippi River
basin: strategies to counter a persistent ecological problem: ecotechnology-the use of
natural ecosystems to solve environmental problems-should be a part of efforts to shrink
the zone of hypoxia in the Gulf of Mexico. BioScience. 51(5): 373-388.

64

Owen, J. S., S. L. Warren, T. E. Bilderback and J. P. 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.
Schuch, U.K., and D.W. Burger. 1997. Water use and crop coefficients of woody ornamentals in
containers. J. Amer. Soc Hort. Sci. 122(5):727-734.
Southern Nursery Association. 2007. Best management practices: Guide for producing nursery
crops. 2nd Ed. Southern Nursery Association, Atlanta, GA.
Tyler, H. H., S. L. Warren and T. E. Bilderback. 1996. Reduced leaching fractions improve
irrigation use efficiency and nutrient efficacy. J Environ Hortic. 14(4): 199-203.
U.S. Environmental Protection Agency. 2003. EPA national drinking water standards. Office of
Water (4604M). EPA 816-F-03-016. 4Mar 2009.
Warsaw, A. L., R. F. Fernandez, B. M. Cregg and J. A. Andresen. 2009a. Water conservation,
growth, and water use efficiency of container-grown woody ornamentals irrigated based
on daily water use. HortScience. 44(5): 1308-1318.
Warsaw, A.L., R. F. 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. Production, HortScience. 44(6): 1573–1580.
Warsaw, A.L., R.T. Fernandez, D.R. Kort, B.M. Cregg, B. Rowe and C. Vandervoort. 2012.
Remediation of metalaxyl, trifluralin, and nitrate from nursery runoff using container-grown
woody ornamentals and phytoremediation areas. Ecol. Eng. 47:254-263.
Yeager, T. H., J. Million, C. Larsen and B. Stamps. 2010. Florida nursery best management
practices: past, present, and future. HortTechnology. 20(1): 82-88.

65

CHAPTER TWO
PHYSICAL PROPERTIES AND COMPOSTABILITY OF ALTERNATIVE CONTAINERS
FOR NURSERY PRODUCTION

66

Abstract
The purpose of this work was to evaluate the use of alternative containers made from
materials other than virgin plastic under nursery conditions. Containers made from recycled
paper and a conventional high density polyethylene (plastic) were used to grow Euonymus
fortunei ‘Roemertwo’ from July 2011 to June 2012. Containers made from recycled paper,
processed poultry feathers, a mixed of natural fiber with recycled plastic fiber and plastic were
used to grow Buxus x ‘Green Velvet’ from June 2012 to June 2013. Changes in the mechanical
strength and physical properties of the containers were recorded. Compostability of the
alternative containers was tested using ASTM D6868 and 6400 (ASTM, 2004, 2011).
Alternative containers, except the one made from recycled plastic fiber mix, had greater
compression strength than plastic containers. Fiber container sidewalls had a higher water vapor
transmission rate than that of plastic containers. According to ASTM D 6400, a compostable
product produced with a heterogeneous structure must degrade 90% during simulated
composting when compared with a cellulose positive control, pass the disintegration test and
ecotoxicity test. All containers passed the ecotoxicity test, however, failed the composting test.
Therefore alternative containers in this experiment were not proven to be compostable according
to ASTM standards.

67

Introduction
Plastic containers are traditionally used by greenhouse and nursery operations. Despite the
advantages of low cost and light weight, there are several major concerns about using them, such
as disposal issues and environmental pollution. Therefore, there is a need for alternative
containers to improve sustainable nursery practices. Materials such as peat, bioresins, poultry
feathers, wood fiber, paper fiber, rice hull, coir and cow manure compost have been used to
manufacture horticulture alternative containers (Evans and Karcher, 2004; Grayed, 1971;
Kuehny et al., 2011; Lopez and Camberato, 2011).
There are relatively few studies in the literature that evaluate physical properties of alternative
containers. Evans and Karcher (2004) evaluated dry and wet strength of plastic, peat and feather
fiber containers by increasing the amount of pressure on the container using a texture analyzer;
they discovered that peat and feather fiber containers had lower dry and wet strength than plastic
containers. Moreover, the wet strength was much less than dry strength for both the plastic and
fiber containers. Candido et al.(2007) evaluated the tensile strength behavior and chromatic
characteristics of traditional polypropylene containers and biodegradable plastic containers
during a five month experiment in the greenhouse, finding that the tensile strength of
biodegradable plastic containers decreased over time, and all containers except traditional
containers exhibited discoloration. Schettini et al. (2012) tested the physical-chemical
characterization of containers made from tomato and hemp fibers with mechanical, water vapor
permeability tests, and morphological analysis. They discovered that there was a correlation
between polymer cross-linking, water diffusion and mechanical performance.
A few studies tested the biodegradability or decomposition ratio of the containers available on
the market. Evans and Karcher (2004) planted plants with intact plastic, peat and feather

68

containers for 16 weeks and evaluated the decomposition ratio, defined as the ratio of the weight
of the containers before and after planting; they found that the decomposition ratio was greater
for feather containers than that of peat containers when vinca and marigold were grown in the
containers. Candido et al. (2007) evaluated container degradation by visual assessment, finding
containers made from biodegradable plastic with 10% and 20% compostable materials were not
suitable for Poinsettia cultivation as they showed lesions on the basal surface and at the edge of
the container during the production period. Ahn et al. (2011) tested the biodegradability of
containers constructed of polylactic acid and poultry feather fiber by measuring the CO2
produced during composting incubation; they also used near infrared spectroscopy to estimate
the chemical composition of container material that resulted during degradation. They found that
the poultry feather fiber did not degrade during the compost period and the polyactic acid
underwent chemical changes during polymer extruding and molding which inhibited
biodegradation. None of the experiments stated above used ASTM standards to determine the
compostability of alternative containers.
The goal of this study was to study the performance of alternative containers in nursery
production using ASTM standards. In order to achieve this goal, this experiment focused on the
following specific objectives: 1) evaluating the physical property changes of alternative
containers under nursery practices; 2) assessing the compostability of alternative containers with
ASTM D6868 and 6400.

69

Material and Methods
Site specifications and plant material
The experiment was conducted at the Michigan State University Horticulture Teaching and
Research Center (HTRC) located in Holt, MI. The HTRC is located at latitude 42.7º N, longitude
84.5º E, and elevation 264 m. Air temperature, relative humidity, and solar radiation recorded
during the experiments are shown in Fig 2.1 a-c, the total radiation was 4704 MJ· -2 from 2011
m
to 2012 and 4687 MJ· -2 from 2012 to 2013. During winter, the experimental site was covered
m
with white plastic film providing 70% shade for winter protection, therefore, the plants and
containers experienced less solar radiation as indicated in Figure. 2.1 –c during this period.
Plants were selected based on capability of tolerating USDA cold hardiness zone 5-8
conditions since this was part of a multi-state project. Euonymus fortunei ‘Roemertwo’ was used
in the alternative container study in 2011. Plants were transplanted from 5-cm plugs into
treatment containers on 1 June 2011.

Container substrate consisted of 85% pine bark: 15%

peat-moss (vol: vol). Plants were fertilized on 5 June with 26 g per container of a 17.0N-3.5P6.6K fertilizer, which contained micronutrients and had a nutrient release period at 27℃ of 4
months (HFI Topdress special; Harrell’s Inc., Lakeland, FL). Buxus x‘Green Velvet’ was
used in the 2012 study. Plants were potted up on 14 May and received the same fertilizer as 2011
on 5 June, 2012.

70

Figure 2.1. Air temperature (A), relative humidity (B) and solar radiation (C) at the Michigan
State University Horticulture Teaching and Research Center weather station from June 2011 to
June 2013

71

Experimental design
This was a one factor completely randomized design experiment. Each of the twelve
irrigation zones served as one treatment replicate; each container type was replicated three times
and randomly assigned to the irrigation zones. Containers were spaced 32 cm apart on center and
located at the middle of irrigation zone. In each irrigation zone, there were fifteen containers in
three rows of five with twenty guard plants surrounding the border to minimize edge effects.
Container treatment types and information can be found in Table 2.1. Western pulp (WP) and
Kord fiber (Kord) containers were both made from up to 72% recycled paper. Keratin (KR)
containers contained processed poultry feathers and recycled plastic. The components of Root
pouch (RP) containers were recycled plastic fiber and natural fibers.

72

Table 2.1. Container treatments used in 2011 and 2012 alternative container studies.
Treatment
Abbreviation
Top
Height Volume
Manufacture
diameter
(cm)
(liter)
(cm)
2011
Polyethylene
Plastic
19.05
18.10
3.78
Nursery Supplies Inc.,
PS400-SM
Chambersburg, PA
Western Pulp
7X7RD

WP

18.70

17.10

3.89

Western Pulp Products
Co., Jacksonville, TX

Kord 07.50 Fiber
Grow Nursery Pot

Kord

19.05

17.78

3.94

Texon Polymer Group
Inc., Waco, TX

Plastic

19.05

18.10

3.78

Nursery Supplies Inc.,
Chambersburg, PA

Western Pulp
7X7RD

WP

18.70

17.1

3.89

Western Pulp Products
Co., Jacksonville, TX

Root pouch 15-20
month

RP

15.24

17.78

3.36

Central bag& Burlap,
Denver, CO

Keratin container

KR

16.51

17.78

2.95

Horticultural Research
Institution,
Washington, DC

2012
Polyethylene
PS400-SM

Irrigation application
The irrigation was delivered by a solenoid-controlled overhead system. Nine Toro 570
Shrub Spray Sprinklers (The Toro Company, Riverside, CA) were mounted on 0.66m high, 1.3
cm diameter risers in each irrigation zone spaced 2.50 m apart. Each irrigation zone had four 90
degree emitters located at four corners of the beds with four 180 degree emitters placed in the
middle of the four sides; two 360 degree emitters were placed at the center of irrigation zone.
The irrigation zone area was 4.5 m long and 7.5 m wide. All irrigation was directed into the zone
with a 2.44-m radius distance of throw. Distribution uniformity of each bed was measured at 0.8
73

or greater during a period without wind. In 2011, two soil moisture sensors (model EC5,
Decagon Devices, Inc., Pullman, WA) were inserted into two containers for each zone to
determined plant daily water use (DWU); in 2012, two different soil moisture sensors (model
GS3, Decagon Devices, Inc., Pullman, WA) per zone were used to determined DWU in addition
to the EC5 sensors. The irrigation was applied to replace total DWU back to the containers and
was based on the average DWU of the two containers in each zone with moisture sensors. For a
detailed description of how DWU was determined see Chapter 3. Irrigation was split into two
applications per day initiated at 0700HR and 1900HR.

Container physical properties
In 2011, two containers from each replicate were harvested at month 1, 2, 4, 6, 8 and 12
(June 2011=month 0) and taken to Michigan State University School of Packaging laboratory for
physical property tests. In 2012, two containers from each replicate were harvested at month 2,
6, and 12 (June 2012=month 0).
The containers were pre-conditioned according to ATSM D685 (ATSM, 2012). A squeezer
(Lansmont Corporation, Monterey, CA) was used to test compression strength of the container
using a fixed platen moving at 0.05 in/div. The platen stopped moving when the container
showed 0 preload and 20% deformation yield. A Squeezer Reader version 2.0.0 (Lansmont
Corporation, Monterey CA) was used to interpret and record data.
A universal tester machine from Instron, Inc. (Norwood, MA) was used to test tensile
strength for each RP container sample according to ASTM D3822 (2007). The samples were
pre-conditioned in a humidity bucket at 23 ° and 62 ±2% relative humidity (RH) for 72 hours
C
according to ASTM D1776 (2009). After conditioning, 2.54 cm x 12.7 cm strips of fabric were

74

cut out on the vertical direction of the RP. Ten sample strips of each container were tested. The
strips were fixed by the upper and lower clamps to create stiff tension. The tester began to
elongate the fabric and stopped at the point of fabric breakage.
Measurement of water vapor transmission rate (WVTR) was conducted according to
ASTM E 96-95 (1995). For each treatment, two round pieces were cut from each container (3
containers in total) and then fitted into a methacrylate cell (permeation cell) with an inner
diameter of 4.50 cm and inner depth of 2 cm. Three permeation cells of each container type were
filled with desiccant and another 3 cells left empty. The cells were then placed in an
environmental chamber set at 85% RH and 37.8℃. The weight of cells was measured by a
Discovery DV314C microbalance (Chaus Corportation, Pine Brook, NJ) approximately every
hour for WP and RP, and twice a day for Plastic and KR until the weight reached equilibrium.
The WVTR was determined as the difference between initial cell weight and final cell weight
then divided by cell surface area and elapse time.

Fourier transform infrared spectroscopy (FTIR)
For each container, the samples were dried in a vacuum oven (Model 1410, Sheldon
Manufacturing Inc., Cornelius, Oregon) at 60°C for 48 hours. Three samples cut from the
container wall and the bottom and were scanned on both sides using a Shimadzu IR-Prestige 21
(Columbia, MD) at the range of 650 to 4000 cm-1 with the following settings: no. of scan 40,
resolution of 4 cm-1, absorbance to detect any changes in the spectra shifts which associated with
the formation and destruction of functional groups of the container material.

75

Compostability
The compostability tests were conducted according to ASTM Standard D 6400 (ASTM,
2004). The tests included a biodegradation test and an ecotoxicity test.
A direct measurement respirometric (DMR) system (Kijchavengkul et al., 2006) was used for
the biodegradability test. Triplicate bioreactors were used for each treatment (compost mixed
with alternative container material) and the control (compost only). Each bioreactor was filled
with approximately 500 g compost consisting of 80% manure blend and 20% vermiculite. In
2011, 8 g container material for each treatment was ground into powder and added to the
compost. In 2012, the container material for each treatment was cut into 1 x 1 cm pieces and
added into the compost. The bioreactors were set to 58± 2 ℃, 55 ± 5% RH with an air flow rate
at 40±5 cc· -1 for 90 days. The carbon component of the material was determined by Serious
min
II CHNS/O Analyzer 2400 (PerkinElmer, Waltham, Massachusetts). The degree of degradation
was defined as the percentage of mineralization by the following equation (Kijchavengkul et al,
2006), namely the proportion of carbon molecules of the material converted to CO2 due to
microbial respiration, where gCO2 – gCO2 means the difference between the mass of total
evolved CO2 and blank CO2 (g), gmat is the mass of the test material (g) and %Cmat is the
percentage of carbon content in the test material:
gCO2 −gCO2 b
% Mineralization =
%Cmat 44 ×
gmat 100 22

76

100

The ecotoxicity tests include heavy metal analysis, plant germination test and growth test.
The WP and Kord containers were sent to Soil Control Lab (Watsonville, California, USA) for
heavy mental analysis. The germination test was carried out as part of the biodegradable test
according to ASTM D6868, 6400, and OECD Guideline 208 Terrestrial Plants, Growth Test. In
2011, cucumber and onion seeds (Seedway, Hall, NY) were selected to conduct the germination
tests; in 2012, cucumber and oat seeds (Botanical Interests Inc., Broomfield, CO) were used. Ten
15.24 cm diameter plastic dishes were used for each treatment compost and control compost
(compost only) after the incubation from the biodegradability test. Each dish was filled 75 g
potting substrate and 75 g treatment compost or 75 g of control compost. For each treatment, five
dishes were evenly seeded with 30 cucumber seeds per dish and the other five dishes were
seeded with 30 onion (2011) or 30 oat grass seeds (2012) per dish. The dishes were transferred
into a greenhouse at 25℃, 95% RH. The dishes were irrigated until saturation every other day,
and the germination rate was recorded daily. After three weeks, the plants were harvested and
cleaned. Height and fresh weight of the plants were measured. The plants were oven dried at
70° until the weight reached constant and dry weight was then recorded.
C

Statistical analysis
Physical property test results and germination data were analyzed using PROC GLM
procedure of statistical analysis software (SAS Version 9.2; SAS institute, Cary, NC) with Tukey
adjustment at 0.05 significance level. The compression strength was analyzed using PROC REG
procedure of SAS.

77

Results and Discussion
Compression strength
In 2011, the compression strength of Kord and WP containers were reduced during the 12month experimental period (Figure 2.2). The WP had greater or similar compression strength
compared to that of Kord containers during the experimental period. The compression strength
decreased rapidly for both Kord, from 367 lbs. at month 0 to 262.5 lbs. at month 4, and WP
containers, from 633 lbs. at month 0 to 379 lbs. at month 4. This reduction in compression
strength can be explained by photo-degradation, thermal and hydrolysis reactions, and
biodegradation resulting from irrigation and solar radiation.
In 2012, the RP container was not included in the compression test due to its deformable
structure. The compression strength of the WP containers at month 0 was 600 lbs. in 2011 and
400 lbs. in 2012 (Figure 2.3). This data suggests that manufactured components of WP
containers had changed between 2011 and 2012. The compression strength of WP decreased
throughout the experiment from 409 lbs. at month 0 to 234 lbs. at month 12. The KR containers
had the highest compression strength compared to other containers; conversely, plastic
containers had the lowest compression strength. There was no change in compression strength of
either KR or plastic during the experiment. The compression strength difference between plastic
containers and WP and Kord containers may be attributed to strength differences in plastic
polymers and wood fiber.
Evans et al. (2010) tested the dry vertical strength of plastic container and paper container
walls by crushing the containers vertically for 30 mm, finding that the amount of pressure needed
between the two container types was similar. The difference between Evans’ result and this

78

experiment is that the paper container used in Evan’s test was produced from paper pulp with
binder while WP containers were made from post-consumer paper and molding technique.

Figure 2.2. The compression strength for Kord fiber (Kord) and Western pulp (WP) containers
from May 2011 to May 2012

Figure 2.3. The compression strength for Western pulp (WP), Plastic and Keratin (KR)
containers from June 2012 to June 2013.
*NS = No significance

79

Tensile strength of RP containers
The tensile strength of RP containers generally decreased during the experiment (Table 2.2).
The extension at break length decreased from 32.32 mm at month 0 to 16.08 mm at month 12.
Modulus is the ratio of stress to strain. The modulus of RP containers increased from 22.94 at
month 0 to 32.69 at month 12. These results indicate that the fiber of RP containers underwent
weathering after being in the field for two months, and cross-linking of the polymers might have
occurred during this process due to photo-degradation and oxidation. Candido et al. (2007) also
found that the tensile strength of biodegradable containers decreased during 6 months of
experiment period placed inside of greenhouse.

Table 2.2. Tensile strength test result of root pouch container under field condition for 0, 2, 6 and
12 months
month
0
2
6
12

Extension at
yield (mm)
x
26.51a
13.56b
12.69b
12.29b

Load at
yield (N)
44.65a

Extension at
break (mm)
32.32a

Load at
break (N)
13.39b

Strain at
yield (%)
20.98a

29.94ab
23.30b
37.54ab

17.50b
15.82b
16.08b

8.96b
25.10a
10.84b

Modulus
(Mpa)
22.94b

10.70b
10.00b
9.68b

35.19a
34.80a
32.69ab

x

Means with the same letter in the same column is not significantly different (α=0.05)

Water vapor transmission rate (WVTR)
In 2011, the WVTR of Kord containers was greater than that of WP containers. The WVTR
of Kord containers remained constant throughout the experiment (Table 2.3). The WVTR of WP
containers increased from 1.42 kg· -2· -1 · -5 at month 0 to 1.76 kg· -2· -1 · -5 at month
m s 10
m s 10
12, which could be caused by scissoring of the polymer chain resulting from thermal and
hydrolysis degradation.
80

In 2012, the WVTR of RP containers was greater than that of WP containers, which was
greater than KR containers (Table 2.4). The WVTR of RP containers dropped from 6.21 kg· m
2

· -1 · -5 at month 0 to 2.36 kg· -2· -1 · -5 at month 12, which could be explained by
s 10
m s 10

cross-linking of the polymer chains. The WVTR of WP and KR containers remained nearly
unchanged during 6 months under field condition. The KR container had the lowest WVTR
probably due to the high thickness of the container wall.

Table 2.3. Water Vapor Transmission Rate (WVTR) of Kord and Western pulp (WP) container
under field conditions from June 2010 to June 2011 for month 0, 2, 6 and 12
WVTR (kg· -2· -1 · -5)
m s 10
Container
month 0
month 2
month 6
month 12
date
(new container)
(9/1/11)
(1/8/12)
(6/13/12)
Kord

1.73ax Ay

1.81aA

1.81aA

1.78aA

WP
1.42bB
1.65aB
1.68aB
1.76aB
x
Means with the same lowercase letter in the same row are not significantly different (α=0.05)
y

Means with the same uppercase letter in the same column are not significantly different
(α=0.05)

Table 2.4. Water Vapor Transmission Rates (WVTR) of Western pulp (WP), Root pouch (RP),
and Keratin (KR) containers from June 2011 to June 2012 for month 0, 2, 6 and 12
WVTR (kg· -2· -1 · -5)
m s 10
Container
date

month 0
(new container)

month 2
(8/20/12)

month 6
(1/6/13)

month 12
(6/25/13)

WP

1.43axBy

1.33abB

1.23bcB

1.11cB

RP

6.21aA

5.81aA

3.03bA

2.36cA

KR
0.00105aC
0.0111aC
0.000554aC
0.00424aC
Means with the same lowercase letter in the same row are not significantly different (α=0.05)

x
y

Means with the same uppercase letter in the same column are not significantly different
(α=0.05)

81

FTIR
For the WP containers, there are formations of new peaks at wavenumber 1410 (scissoring
vibration of CH2) and 873 cm-1 (skeletal vibration of CH2 or out-of-plane ring stretching in
cellulose) indicating changes in the cellulose main chain due to weathering (Figure 2.4). For the
Kord fiber pot (Figure 2.5), there are formations of new peaks at wavenumber 1648 (C=O with
intramolecular hydrogen bonds) and 1320 cm-1 (wagging vibration of CH2) as well as a reduction
in absorbance at wavenumber 1110 cm-1 (C-O-C stretching of glycosidic bond) indicating main
chain scission or depolymerization of the cellulose fiber.

82

Figure 2.4. Fourier transform infrared spectroscopy of Western pulp containers outside wall of
experimental month 0, 4, 8 and 12 in 2011

83

Figure 2.5. Fourier transform infrared spectroscopy of Kord containers outside wall of
experimental month 0, 4, 8 and 12 in 2011

84

Compostability
In 2011, after 49 days of the biodegradation test, the percent mineralization rate of Kord, WP
and cellulose powder were 89.7, 93.0 and 98.6%, respectively (Figure 2.6). In 2012, after 90
days of the biodegradation test, the percent mineralization rate of KP, RP, WP, and cellulose
powder were 20.5, 13.2, 26.1, and 92.4%, respectively (Figure 2.7). The mineralization value of
the control groups in both years were greater than 90% as specified in ASTM D6868 standard
(ASTM, 2011). In 2011, Kord and WP were ground to a powder, while in 2012 KP, RP and WP
were cut into 1 cm x 1 cm pieces. Although both methods are according to ASTM D 6400, the
larger size in 2012 may have resulted in the containers not being considered biodegradable.
Barker (1997) reported that the decomposition will be accelerated when the surface area is
increased by grinding or shredding when nitrogen is available. Ahn et al. (2011) also found that
poultry feather fibers did not degrade during incubation in dairy manure compost inoculum.
These limitations should be considered in the case that these containers will be disposed of with
farm composting processes.

85

Figure 2.6. Mineralization ratio of Western pulp (WP), Kord container comparing to cellulose
powder in manure compost at 58℃ and 55% relative humidity during 50 day of direct
measurement respirometric experiment

86

100
90

Cellulose powder
KP
RP
WP

80

% Mineralization

70
60
50
40
30
20
10
0
0

20

40

60

80

100

Day of Experiment

Figure 2.7. Percent Mineralization of cellulose powder, Keratin (KR), Root pouch (RP) and
Western pulp (WP) container in manure compost at 58℃ and 55% relative humidity during 90
days of direct measurement respirometric experiment

87

In 2011, both WP and Kord containers passed heavy metal testing according to ASTM
standards 6868 (2011b) (Table 2.5, 2.6). In 2012, heavy mental tests were not conducted since no
alternative containers passed the biodegradation test.
In the 2011 germination test, the average germination rate of onion in Kord, WP and control
compost was 90%, 92% and 91.3% (Table 2.7). The average germination rate of cucumber in
Kord, WP and control compost was 96%, 94% and 95.3%. Both Kord and WP meet the
requirement of germination according to ASTM D6868 since the germination rates of onion and
cucumber were greater than 90% of the rate in control compost. Similar to 2011, in 2012 seed
germination test, the germination rate of cucumber in WP, KR, RP and control compost was
96%, 96.7%, 96.7% and 90% (Table 2.8). The germination rate of oat in WP, KR, RP and
control compost was 100%, 100%, 98.7% and 98%. These results indicate that WP, KR and RP
containers meet the requirement of germination according to ASTM D6868 since the
germination is higher than 90% of that of control compost. The average shoot height of oat
seedlings and cucumber was 16.00 cm and 10.39 cm with no difference between treatments. The
average dry weight of oat and cucumber was 0.533 gram and 1.131 gram with no difference
between treatments (data not shown).

88

Table 2.5. Heavy mental concentration result of Kord containers.
Results
Reporting
mg/Kg dry
Analyte
weight
Limit
US
Arsenic (As)
less than 0.5
0.5
Pass
Cadminum (Cd)
less than 0.5
0.5
Pass
Copper (Cu)
29
Lead (Pb)
0.56
Mercury (Hg)
less than 0.2
Nickel (Ni)
12
Selenium (Se)
less than 0.5
Zinc (Zn)
14
Cobalt (Co)
less than 0.5
Chrominum (Cr)
7.2
Molybdenum (Mo)
1.6
*NA means ‘not applicable’

0.5
0.5
0.2
0.5
0.5
0.5
0.5
0.5
0.5

Pass
Pass
Pass
Pass
Pass
Pass
NA
NA
NA

Region
Canada Europe Janpan
Pass
Pass
Pass
Pass
Pass
Pass
NA*
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
NA
Pass
Pass
Pass
Pass
NA
NA
NA
Pass
Pass
Pass
Fail
NA

Table 2.6. Heavy mental concentration result of Western pulp containers.
Results
Reporting
Region
Analyte
mg/Kg dry weight
Limit
US
Canada Europe Janpan
Arsenic (As)
less than 0.5
0.5
Pass
Pass
Pass
Pass
Cadminum (Cd)
less than 0.5
0.5
Pass
Pass
Pass
Pass
Copper (Cu)
18
0.5
Pass
NA*
Pass
Pass
Lead (Pb)
1.1
0.5
Pass
Pass
Pass
Pass
Mercury (Hg)
less than 0.2
0.2
Pass
Pass
Pass
Pass
Nickel (Ni)
14
0.5
Pass
Pass
Pass
Pass
Selenium (Se)
less than 0.5
0.5
Pass
Pass
Pass
NA
Zinc (Zn)
13
0.5
Pass
Pass
Pass
Pass
Cobalt (Co)
less than 0.5
0.5
NA
Pass
NA
NA
Chrominum (Cr)
2
0.5
NA
NA
Pass
Pass
Molybdenum (Mo)
1.6
0.5
NA
Pass
Fail
NA
*NA means ‘not applicable’

89

Table 2.7. Onion and cucumber seed germination rate in control compost (compost only) and final
compost containing Kord fiber pot or Western pulp (WP) containers including 5 replicates, average
germination rate and percentage comparing to that of control compost in 2011.
% Germination %
Treatment
Rep1 Rep 2 Rep 3 Rep 4 Rep 5 Average ±S.D.
Control
Onion
Control
26
27
26
28
30
27.4
91.3 ±5.6 100
Kord
24
28
27
29
27
27
90.0 ±6.2 98.5
WP
26
26
29
30
27
27.6
92.0 ±6.1 100.7
Cucumber
Control
28
29
30
28
28
28.6
95.3 ±3.0 100
Kord
29
30
28
27
30
28.8
96.0 ±4.3 100.7
WP
27
29
30
28
27
28.2
94.0 ±4.3 98.6

Table 2.8. Oat and cucumber seed germination rate in control compost (compost only) and final
compost containing Western pulp (WP), Keratin (KR) and Root pouch (RP) containers including
5 replicates, average germination rate and the percentage comparing to that of control compost in
2012.
%
Rep
Rep
Rep
Rep
Rep
Germination
%
Treatment
1
2
3
4
5
Average
+S.D
control
Oat
Control
30
30
28
29
30
29.4
98.0+3
100%
WP
30
30
30
30
30
30
100+0
106.70%
KR
30
30
30
30
30
30
100+0
107.40%
RP
30
28
30
30
30
29.6
98.7+3
107.40%
Cucumber
Control
28
27
26
27
27
27
90.0+2.4
100%
WP
29
28
28
29
30
28.8
96+2.8
106.70%
KR
29
29
29
30
28
29
96.7+2.4
107.40%
RP
29
29
29
30
28
29
96.7+2.4
107.40%

90

Conclusions
The physical properties of the alternative container varied. WP and Kord containers are both
made from molded recycled paper. They have greater compression strength than that of Plastic
containers; however, they have a higher WVTR, which might consume more water than Plastic
containers (Chapter 3). The FTIR test indicated that WP and Kord containers suffer photooxidation from depolymerization and polymer changes under field conditions after 12 months.
These results indicate that when adopting WP and Kord containers, growers could benefit from
their greater compression strength during transportation, however, the containers bottom and rim
may disintegrate after approximately 12 months depending on the nursery local climate and
irrigation practices. RP containers are made from recycled plastic fibers and natural fibers. RP
containers had the greatest WVTR than other containers, which might lead to more water use
(Chapter 3). The tensile strength of RP containers decreased after use in the field for two months
which could cause container damage during transportation. The KR containers are made from
recycled plastic and processed poultry feathers. It had the greatest compression strength than
other containers and a low WVTR, which was similar to the Plastic containers.
In terms of compostability, WP and Kord containers passed biodegradation test when ground
to a powder form but not in 1x 1 cm pieces. Since we do not have the formula of the containers
from the manufacturer, we could not conclude that WP and Kord containers are compostable.
Additionally, alternative containers are often cut into similar sized pieces when being disposed,
and they were not proven to be compostable under this common practice. All containers tested
passed the germination test, showing that the containers had no negative impact on seedling
growth.

91

LITERATURE CITED

92

LITERATURE CITED

Ahn, H. K., M. S. Huda, M. C. Smith, W. Mulbry, W. F. Schmidt, and J. B. Reeves III. 2011.
Biodegradability of injection molded bioplastic pots containing polylactic acid and
poultry feather fiber. Bioresour. Technol. 102(7): 4930-4933.
ASTM. 1995. ASTM E 96-95 Standard test method for water vapor transmission of materials.
ASTM international, West Conshohocken, PA.
ASTM. 2004. ASTM D6400-04 Standard specification for compostable plastics. ASTM
International, West Conshohocken, PA.
ASTM. 2007. ASTM D3822-07 Standard test method for tensile properties of single textile
fibers. ASTM international, West Conshohocken, PA.
ASTM. 2009. ASTM D1776-08 Standard Practice for conditioning and testing textiles. ASTM
international, West Conshohocken, PA.
ASTM. 2011. ASTM D6868-11 Standard specification for labeling of end items that incorporate
plastics and polymers as coating or additives with paper and other substrates designed to
be aerobically composted in municipal or industrial facilities. ASTM International, West
Conshohocken, PA.
ASTM. 2012. ASTM D685-12 Standard practice for conditioning paper and paper products for
testing. ASTM international, West Conshohocken, PA.
Barker, A. V. 1997. Composition and uses of compost. In ACS Symposium Series (Vol. 668, pp.
140-162). Washington, DC: American Chemical Society.
Candido, V., V. Miccolis, D. Castronuovo and C. Manera. 2007. Poinsettia (euphorbia
pulcherrima) cultivation in biodegradable pots: mechanical and agronomical behaviour
of pots and plants traits. In International Symposium on High Technology for
Greenhouse System Management. Greensys 801: 1563-1570.
Evans, M. R and D. Karcher. 2004. Properties of plastic, peat, and processed poultry feather fiber
growing containers. HortScience. 39(5): 1008-1011.
Evans, M. R., M. Taylor and J. Kuehny. 2010. Physical properties of Biocontainers for
greenhouse crops production. Horttechnology, 20 (3), 549-555.
Kijchavengkul, T., Auras, R., Rubino, M., Ngouajio., Fernandez, R.T. 2006. Development of an
automatic laboratory-scale respirometric system to measure polymer biodegradability.
Polymer testing, 25(8), 1006-1016.

93

Kuehny, J. S., M. Taylor and M. R. Evans, 2011. Greenhouse and landscape performance of
bedding plants in biocontainers. Horttechnology. 21(2): 155-161.
Lopez, R. G. and D. M. Camberato, 2011. Growth and development of ‘Eckespoint Classic Red’
poinsettia in biodegradable and compostable containers. Horttechnology. 21(4): 419-423.
Schettini, E., G. Santagata, M. Malinconico, B. Immirzi, G. Scarascia Mugnozza and G. Vox.
2012. Recycled wastes of tomato and hemp fibres for biodegradable pots: physicochemical characterization and field performance. Resources, Conservation and
Recycling. 70: 9-19.

94

CHAPTER THREE
PLANT GROWTH AND WATER USE IN ALTERNATIVE CONTAINERS FOR NURSERY
PRODUCTION

95

Abstract
This one-factor completely randomized experiment was conducted at the Michigan State
University Horticulture Teaching and Research Center to test plant growth and water use in
containers made from material other than virgin plastic. From July 2011 to June 2012, Euonymus
fortunei ‘Roemertwo’ were planted in three types of #1 (~3.8 L) containers and evaluated.
Container types were: 1) polyethylene PF400-SM (Plastic); 2) Western Pulp 7X7RD (WP); 3)
Kord 07.50 Fiber Pot (Kord). From June 2012 to May 2013, Buxus x ‘Green Velvet’ were
evaluated in four types of #1 containers: 1) Plastic; 2) WP; 3) Root pouch 15-20 month (RP) 4)
Keratin pot (KR). Substrate volumetric moisture content (Ɵ) was determined by EC-5 moisture
sensors in 2011; GS3 and EC-5 sensors were used in 2012 (Decagon Devices, Inc., Pullman,
WA). Volumetric substrate moisture was measured 5 min after irrigation application (θAI), and
immediately before the next irrigation (θBI). The DWU was determined by the difference
between θAI and θBI multiplying container volume. Plants were irrigated to replace 100% DWU.
For E. fortunei, the plant final growth index was not different between treatments. Plants grown
in the Plastic containers had a greater root and leaf biomass than that of WP and Kord containers.
The seasonal average DWU of plants grown in WP and Kord containers was greater than that of
Plastic containers. The mortality rate of plants grown in WP and Kord containers was 2% in
October 2011 and 52% in May 2012. The mortality rate of plants grown in Plastic containers was
13% in October 2011 and 15% in May 2012. For Buxus x Green Velvet, the final growth index
of plants was similar between treatments. The dry leaf weight of plants grown in KR containers
was greater than that of plants grown in WP containers. Plants grown in KR containers had the

96

least water use while plants in Plastic had the highest water use. The mortality of Buxus was 0%
for all treatments.

Introduction
Plastic containers are the most commonly used pots for container production in nursery and
greenhouse operations. In nine southern states, the value of containers purchased by growers
totaled $16.6 million, 99% of which were polyethylene (Hodges and Haydu 2001). The light
weight and low cost of plastic material are the primary reasons for use in container production,
however, there are environmental and sustainability concerns when using plastic containers.
Disposal issues with used plastic containers is a growing concern. Today, the primary method
of plastic container disposal is in the landfill. Since plastic has only been produced in large
quantities for around 60 years, its longevity in the natural environment remains uncertain, therefore
long term risks of soil and ground contamination from UV stabilizers and additives used in plastic
products are unknown (Hopewell et al., 2009; Teuten et al. 2009). Incineration is a disposal
alternative that reduces the landfill space needed for plastic waste; however, burning results in
toxic gas and carbon dioxide emissions, which contributes to climate change (Anand et al., 2007;
Hopewell et al., 2009).
Secondly, the overriding manufacturing concern is that the current plastic container
production is not sustainable; approximately 4 percent of annual petroleum production is used to
make plastic plus a similar amount of petroleum is used to provide the needed energy in the
production process (Thompson et al., 2009). Yet no widespread recycling is evident and the
containers will be ultimately discarded by commercial or end users (Evans and Hensley, 2004).
In order to solve these economic and environmental issues, new materials such as bioresins, coir,

97

poultry feathers, paper fibers, rice hulls and processed cow manure are being investigated for
biodegradable and compostable containers are being developed and evaluated (Evans et al. 2004;
Hall et al. 2005).
Limited research to date has compared plant growth and water use in alternative containers to
plastic containers. Evans and Hensley (2004) found that when vinca and impatiens were irrigated
according to plant needs, plants grown in poultry feather and peat containers required more
irrigation than plastic containers. They also reported that the shoot dry weight of impatiens and
vinca plants in poultry feather containers were greater than that of peat and plastic containers.
When the plants were irrigated uniformly, vinca had a greater shoot dry weight grown in plastic
containers than peat or feather containers, and there was no difference for impatiens. Lopez and
Camerato (2011) evaluated Poinsettia growth in alternative containers and plastic containers,
finding Poinsettias grown in molded fiber had better growth compared to wheat starch-derived
bioresins and plastic containers when irrigated as necessary with water-soluble fertilizer.
The research above indicates that the plants in biodegradable containers have similar or better
performance than plants grown in the plastic containers in the greenhouse when the water supply
is sufficient. Yet there are no experiments comparing plant growth between biodegradable and
plastic containers under outdoor nursery practices. This experiment assesses plant growth and
water use in alternative and plastic containers. The objectives were to: 1) assess plant growth and
biomass in alternative and plastic containers; 2) determine the water usage of woody ornamental
plants in alternative and plastic containers; 3) determine the suitability of alternative containers
for a one-year production cycle of woody ornamental plants under outdoor nursery conditions.

98

Material and Methods
Site specifications and experimental design
The experiment was conducted at the Michigan State University Horticulture Teaching and
Research Center (HTRC) located in Holt, MI. The HTRC is located at latitude 42.7º N, longitude
84.5º E, and elevation 264 m.. A 250 m2 hoophouse was separated into 12 irrigation zones with
each zone serving as a treatment replicate. The hoophouse was covered with 70% white plastic
film during the winter (mid-November through mid-May) for crop protection. A one factor
completely randomized design was utilized. Each container type (treatment) was replicated three
times with 15 sub replicates and randomly assigned to an irrigation zone (replicate). Containers
were spaced 32 cm apart on center and located in the middle of the irrigation zone in three rows
of five with twenty guard plants surrounding the border to minimize edge effects.

Plant material and treatments
In 2011, Euonymus fortunei ‘Roemertwo’ were transplanted from 5-cm plugs into #1
containers on 1 June and evaluated through May 2012. Container substrate consisted of 85%
pine bark: 15% peat-moss (vol: vol). Plants were fertilized on 5 June with 26 g per container of a
17.0N-3.5P-6.6K fertilizer, which contained micronutrients and had a nutrient release period at
27℃ of 4 months (HFI Topdress special; Harrell’s Inc., Lakeland, FL). Container treatments in
2011 were: 1) polyethylene PF400-SM (Plastic); 2) Western Pulp 7X7RD (WP); 3) Kord 07.50
Fiber Pot (Kord). In 2012, Buxus x ‘Green Velvet’ were potted from 5-cm plugs into #1
containers on 14 May with the same substrate mixture and evaluated through May 2013. Plants
received the same fertilizer as used in 2011 on 5 June, 2012. Container treatments in 2012 were:

99

1) Plastic; 2) WP; 3) Root pouch 15-20 month (RP) 4) Keratin pot (KR). A detailed description
of the containers is provided in Table 2.1 (Chapter 2).

Irrigation application and daily water use (DWU)
The irrigation was delivered by a solenoid-controlled overhead system. Nine Toro 570 Shrub
Spray Sprinklers (The Toro Company, Riverside, CA) were mounted on 0.66m high, 1.3 cm
diameter risers in each irrigation zone spaced 2.50 m apart. Each irrigation zone had four 90
degree emitters located at four corners of the beds with four 180 degree emitters placed in the
middle of the sides; two 360 degree emitters were placed at the center of irrigation zone. Each
irrigation zone is 4.5m long and 7.5m wide. All irrigation was directed into the block with a
2.44-m radius distance of throw. Distribution uniformity of each bed was measured at 0.8 or
greater during a period without wind. In 2011, two EC5 (Decagon Devices Inc., Pullman, WA,
USA) sensors were inserted into two containers for each zone to determined plant daily water
use (DWU); in 2012, two GS3 (Decagon Devices Inc., Pullman, WA, USA) sensors per zone
were used to determined DWU. The probes were inserted in the northeast side of the containers,
centered between plants and the container edge, to maximize the probe reading uniformity and
accuracy. The sensors were calibrated by correlating the datalogger reading with container
weight change during a substrate dry down cycle. The probe readings were recorded by a
datalogger (model CR1000, Campbell Scientific Inc., Logan, UT, USA) every 15 minutes.
Volumetric substrate moisture was measured 5 min after irrigation application (θAI), and
immediately before the next irrigation (θBI). The DWU was determined by the equation: DWU=
(θAI-θBI) x container volume. The container was saturated on the first day of experiment. The
irrigation was applied to replace total DWU back to the containers and was based on the average

100

DWU of two containers in each zone. Irrigation was split into two applications per day initiated
at 0700HR and 1900HR.

Plant growth index and biomass
Plant growth index (GI) was measured approximately every two weeks. GI was calculated
as GI= (height+width1+width2)/3, where the plant height was taken from the rim of the
container to the highest point of the plant, width1 was the width of the plant in the north to south
direction and width 2 was the width of the plant in the west to east direction using fixed pot
labels to maintain orientation. In 2011, the plants were harvested and separated into roots, stem,
and leaves on May 23. The plant materials were dried in a Partlow 1400 oven (The GRIEVE
Corporation, Round Lake, Illinois) at 73 °C for two weeks and then the weights were recorded.
In 2012, the plants were harvest on May 31 with the same methods used to determine dry weight.

Leachate EC, pH and root zone temperature
Electrical conductivity（EC）and pH was measured approximately every month using the
pour through method described by Yeager (2003). A plastic tray was placed under the container
30 minutes after irrigation was applied, then 200 ml reverse osmosis water was added to the
container, a bulb syringe was used to extract leachate from the tray and release it onto the sensor
of a Cardy Twin EC Meter and Cardy Twin PH Meter (Spectrum Technologies, Inc., Illinois
60585). Four of the fifteen replicate containers in each block were randomly selected at the first
measurement and repeatedly measured afterwards. The root zone temperature was measured by
thermistors (model 107-LC Campbell Scientific Inc., Logan, UT, USA) connected to the
datalogger. The probe was inserted between plants (in the center of the containers) and the

101

container edge into one randomly selected subreplicate container in each replicate. The
datalogger was programmed to record the temperature from each probe every 15 min.

Statistical analysis
Growth index, EC and pH were analyzed as repeated measurements using PROC MIXED
procedure of Statistical Analysis Software (SAS Version 9.2; SAS Institute, Cary, NC). When
significant at the 0.05 level, treatment means on each measurement day were separated using a t
test in the PDIFF option of the LSMEANS statement and the SLICING option of PROC MIXED
(α=0.05). Temperature and DWU were analyzed using PROC GLM procedure of SAS and,
when significant, means were separated using Tukey’s test at 0.05 significance level.

3. Results and Discussion
DWU
In 2011, the DWU of plants in WP and Kord containers was similar to that of Plastic containers
in the beginning of the season but generally higher than that of Plastic containers after day 50
(Figure 3.1). This can be partially explained by side wall chemical component changes resulting
from UV degradation and more evaporative surface of the WP and Kord containers (Chapter 2).
The seasonal daily average DWU of E. fortunei grown in WP, Kord and Plastic containers was
193, 119 and 30 ml, respectively. The plant DWU in WP containers was the greatest while DWU
in Plastic was the smallest. Similarly, Evans et al. (2010) reported that when irrigated as necessary,
plants grown in paper container use more water and have a lower irrigation interval than that of
Plastic containers. Additionally, they found that the rate of water loss through the container wall
was a major factor affecting water use.

102

In 2012, the seasonal trend of DWU of plant grown in WP, KP, RP and Plastic containers
was similar, high water use in the summer season and then decreased in the fall (Figure 3.2).
Generally, DWU of plants grown in Plastic containers was the highest compared to other
treatments in the summer season but similar to that of WP containers in the fall season. In terms
of seasonal means, among the treatments, plants grown in KR containers had the least water use
while plants in Plastic container had the highest water use. Plants grown in WP containers used
less water than that of Plastic containers, but were higher than that of RP containers. DWU of
Buxus in WP, Plastic, KP, and RP containers were 214.71, 294.68, 159.95, and 191.64 mL,
respectively. The difference in water usage of WP containers in 2011 and 2012 may be due to
changes in manufacturing of the pots (see Chapter 2).

Figure 3.1. Daily water use (DWU) of Euonymus fortunei grown in western pulp (WP), Kord fiber
(Kord) and Plastic containers from June 16, 2011 (Day 0) to Oct 26, 2011. All plants were irrigated
to replace total DWU back to the container.

103

Figure 3.2. Daily water use (DWU) of Buxus x 'Green Velvet' grown in western pulp (WP), keratin
(KR), Plastic and root pouch (RP) containers from June 23, 2012 (Day 0) to Oct 28, 2012. All
plants were irrigated to replace DWU back to the container.

Plant growth and biomass
The final GI of E. fortunei in WP, Kord and Plastic containers was 18.83 cm with no
difference between treatments. The leaf and root dry weights of plants grown in Plastic were
greater than that of WP and Kord containers while the dry stem weight between treatments was
similar (Table 3.1). The mortality rate of plants grown in WP, Kord and Plastic was 2, 2, and
13% on Oct 11, 2011 and increased to 52, 52, and 15% on Jun 6, 2012, respectively. Since there
was no irrigation supply for the hoophouses during winter, the higher mortality rate of plants
grown in WP and Kord containers after the winter could be attributed to faster desiccation of

104

substrate in fiber containers than Plastic containers, which may have also resulted in reduced root
and leaf dry weights of plants in WP and Kord containers.
The final GI of Buxus was 16.65 cm with no difference between container treatments. The
leaf dry weight of Buxus grown in KR containers was greater than that of those grown in WP
containers (Table 3.2); the stem and root dry weights were not different for any treatment.
In this experiment, the plants grown in KR containers performed similarly to Plastic
containers. Evans and Hensley (2004) reported that when irrigation was applied as needed, plants
grown in poultry feather containers had a greater growth than those in Plastic containers. The
poultry feather containers used in their experiment consisted of 15% kraft paper and 85%
processed feather fiber, which provided an available nitrogen resource to the plants. However,
there was no indication that the poultry feather component in KR contributed to plant growth in
the current experiment, which may be due to different keratin container constituents.

105

Table 3.1. Leaves, stem, and root dry weight of Euonymus fortunei grown in Plastic, Western
pulp (WP), and Kord containers on June 6, 2011.
Leaves weight
Container type
Stem weight (g) Root weight (g) Total Weight (g)
(g)
Plastic
WP
Kord
x

8.863ax
6.061b
3.806b

4.814a
5.190a
3.791a

27.822a
21.478b
17.358b

41.499a
32.729a
24.955a

Means with the same letter in the same column are not different (α=0.05)

Table 3.2. Leaves, stem, and root dry weight of Buxus x ‘Green Velvet’ grown in Plastic,
Western pulp (WP), Root pouch (RP) and Keratin (KR) containers on June 14, 2012.
Container type

Stem weight (g)

Root weight (g)

Total Weight (g)

Plastic
WP
KR
RP
x

Leaves weight (g)
11.197abx
10.402b
12.864a
10.559ab

4.043a
3.627a
4.344a
3.279a

9.935a
9.195a
8.297a
8.896a

25.175a
23.224a
25.505a
22.734a

Means with the same letter in the same column are not different (α=0.05)

106

Root zone temperature
In 2011, the seasonal root zone temperature in Plastic, Kord and WP containers was highest in
the summer and then decreased toward fall season (Figure 3.3). The average daily root zone
temperature was greater in Plastic containers than the Kord containers and the Kord containers
had higher temperature than the WP containers. Temperature differences of Plastic, Kord, WP
containers was also similar for maximum temperature and minimum temperature, but the
difference in average temperature between Plastic, Kord and WP containers was primarily due to
differences in maximum temperature. The average seasonal root zone temperature in Plastic,
Kord, WP containers were 22.43, 17.92, and 15.85 ° respectively. The seasonal maximum root
C,
zone temperature in Plastic, Kord, WP containers were 29.67, 22.31, and 18.93 ° respectively.
C,
The seasonal minimum root zone temperature in Plastic, Kord, WP containers were 13.67, 11.05,
and 9.23 ° The higher temperature in Plastic containers was likely due to carbon black additive
C.
in the plastic, which absorbs more heat from solar radiation than other colors.
In 2012, the seasonal trend of root zone temperature in Plastic, KP, WP, and RP containers
was similar to that of 2011. All containers had higher temperatures in the summer that gradually
decreased into the fall (Figure 3.4). Among treatments, Plastic containers had a higher daily
temperature than WP and RP, but it was similar to KR containers, and the results for maximum
temperature and minimum temperature was similar to that of average temperature. The average
seasonal substrate temperature in Plastic, KR, WP and RP containers were 22.13, 21.12, 20.12,
and 18.84 ° respectively. The seasonal maximum root zone temperature in Plastic, KR, WP
C,
and RP containers were 29.96, 31.40, 27.79 and 25.09 ° The seasonal minimum root zone
C.
temperature in Plastic, KR, WP and RP containers were 14.94, 13.07, 13.62 and 13.01 ° KR
C.
containers were made from bio Plastic resins and were a tan color, so the substrate temperature

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in KR was similar to Plastic containers. RP containers were also black, however, its porous
texture probably allowed better heat dissipation due to evaporative cooling.

Figure 3.3. Substrate temperature in Western Pulp (WP), Kord fiber (Kord) and Plastic containers
located at Horticulture Teaching and Research Center (Holt, MI) from July 20 (Day 0), 2011 to
Oct 27, 2011. Daily average temperature (A) daily maximum temperature (B), daily minimum
temperature(C)

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Figure 3.4. Substrate temperature in Western Pulp (WP), Plastic, keratin (KR) and Root Pouch
(RP) containers from June 10 (Day 0) to Oct 29 (Day 143), 2012. Daily average temperature (A),
daily maximum temperature (B), daily minimum temperature (C).

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Leachate EC and pH
In 2011, the seasonal average leachate EC and pH were 0.421 mS· -1 and 7.4 with no
cm
differences between treatments for any dates measured. In 2012, on day 57 and 85, the substrate
EC in KR containers was greater than in RP container (Figure 3.5). The substrate EC in WP and
Plastic containers were generally in the middle. This is an indication that there was likely more
rapid leachating from RP containers since the RP containers are made from more porous material.
Leachate pH from RP containers was generally higher than that of other containers; however, the
final leachate pH was similar between treatments.

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Figure 3.5. Leachate EC (ms· -1) and pH from Buxus x ‘Green Velvet’ grown in Western pulp,
cm
Keratin, Plastic and Root pouch containers on Experiment day 23, 42, 57, 85, 116 and 114 (day
0=May 14, 2012). Means with the same letter within the same date are not different (α=0.05)

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Conclusions
During 2011 and 2012, plant growth in all alternative containers was similar to those grown in
Plastic containers. This result indicates that the alternative containers do not negatively impact
plant growth.
In 2011, WP and Kord containers used 543.3% and 296.7% more water than that of Plastic
containers, which could be explained by the higher water vapor transmission rate (WVTR) of
WP and Kord containers than that of Plastic containers (Chapter 2). Similarly, Evans et al.
(2010) found more water was required to grow a geranium to marketable size in paper containers
than in plastic containers. They also reported that the rate of water loss through the wall plays a
major role in container water use. The mortality rate of E. fortunei grown in WP and Kord
containers was 2% in October 2011, however, the mortality rate of E. fortunei grown in WP and
Kord containers increased to 52%, higher than that of Plastic containers after being stored in a
hoophouse during winter of November 2011 through May 2012 with no irrigation. Conversely,
there were no Buxus lost to mortality in the 2012-2013 experiment. This suggests that growers
need to consider substrate moisture availability and plant water stress tolerance when WP and
Kord containers are used in climates where winter irrigation is not typical.
RP containers used less water than that of Plastic containers. However, its lower EC indicates
the possibility of leaching of nutrients from the container walls. Therefore using fabric containers
such as RP containers could potentially lead to more nutrient loss. The plants grown in KR
containers required the least amount of irrigation among all containers. This could be provide
another management technique for nursery growers where irrigation usage is limited.

112

LITERATURE CITED

113

LITERATURE CITED

Anand, R.., V. Sharanya, C.N. Murugalakshmi and K. Bhuvaneswari. 2007. Plastic waste- a
hazard to the environment. Everyman’s Sci. 131.
Evans, M. R. and D. L. Hensley. 2004. Plant growth in plastic, peat, and processed poultry
feather fiber growing containers. HortScience. 39(5): 1012-1014.
Hodges, A. W and J. J. Haydu. 2001. Competition in the horticultural container market in the
southeastern United States. Food and Resource Economics Department, Florida
Agricultural Experiment Station, Institute of Food and Agricultural Sciences, University
of Florida.
Lopez, R. G. and D. M. Camberato. 2011. Growth and development of ‘Eckespoint Classic
Red’poinsettia in biodegradable and compostable Containers. Horttechnology. 21(4):
419-423.
Thompson, R. C., C. J. Moore, F. S. vom Saal and S. H. Swan. 2009. Plastics, the environment
and human health: current consensus and future trends. Philos. Trans. R. Soc. Lond., B,
Biol. Sci. 364(1526): 2153-2166.
Teuten, E. L., J. M. Saquing, D. R. Knappe, M. A. Barlaz, S. Jonsson, A. Bjö S. Rowland, R.
rn,
Thompson, T. Galloway, R. Yamashita, D. Ochi, Y. Watanuki, C. Moore, P. Viet, T.
Tana, M. Prudente, R. Boonyatumanond, M. Zakaria, K. Akkhavong, Y. Ogata, H. Hirai,
S. Iwasa, K. Mizukawa, Y. Hagino, A. Imamura, M. Saha and H. Takada. 2009.
Transport and release of chemicals from plastics to the environment and to
wildlife. Philosophical Transactions of the Royal Society B: Biological
Sciences. 364(1526): 2027-2045.
Hopewell, J., R. Dvorak and E. Kosior. 2009. Plastics recycling: challenges and
opportunities. Philosophical Transactions of the Royal Society B: Biological
Sciences. 364(1526): 2115-2126.
Yeager, T.H. 2003. Implementation guide for container-grown plant interim measure. EDIS
Document ENH-895. Environmental Horticulture Department, Florida Cooperative
Extension Service, Institute of Food and Agricultural Sciences, University of Florda.

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CHATPER FOUR
CONCLUSIONS AND FUTURE DIRECTION OF CONTAINER NURSERY IRRIGATION
MANAGEMENT AND ALTERNATIVE CONTAINERS

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Woody Ornamental Irrigation Management
The aim of this project was to discover the impact of plant daily water use (DWU) based
irrigation scheduling on plant growth, runoff volume, runoff nutrient content, substrate electrical
conductivity (EC) and pH.
During the 2011 and 2012 experiment, the plant growth was similar between all irrigation
treatments for all taxa. The water volume applied daily averaged over the season was 79,825
L· -1 in 2011 and 164,912 L· -1 in 2012. The larger irrigation amount in 2012 may have
ha
ha
resulted from larger plant size and higher reference potential evapotranspiration rate (Figure 1.3,
Chapter 1). The daily water runoff volume averaged over the season was 45,457 L· -1 in 2011
ha
and 49,954 L· -1 in 2012. Warsaw et al. (2009a) used the same research site and experimental
ha
design as the current study to evaluate irrigation effects on runoff volume. In Warsaw’s research,
a daily 190,000 L· -1 irrigation rate was applied as the common nursery irrigation rate. The
ha
average runoff volume under this treatment was 114,000 L· -1 per day. Both irrigation and
ha
runoff volume in the current study was much lower than that of common nursery irrigation rate
in Warsaw’s research and would likely have been so if had a similar rate included in this study.
Similarly, Million at el. (2010) also reported that when comparing a plant demand based
irrigation scheduling with a daily 100,000 L·ha-1 irrigation rate, the plant demand-based
irrigation decrease irrigation amount and water runoff volume by 39% and 42% without
affecting the plant growth. Many growers water plants more than needed since they prefer the
risk of more leaching than the consequences of under watering (Yeager et al., 2010). These

116

results demonstrate that growers could irrigate their plants according to the need to reduce
irrigation amount and runoff without concerns about plant growth or quality.
Irrigation scheduling based on plant DWU not only reduced water runoff volume but could
also possibly reduce nutrient loss. In 2012, the daily seasonal average PO43--P load under 10075-75-75 treatment was 56 g·ha-1 which was less than 88 g·ha-1 under 100-75 treatment.
Similar to this result, Owen et al. (2008) performed an irrigation study containerized woody
ornamental crop Skogholm cotoneaster by decreasing leaching fractions (effluent/influent) from
0.2 to 0.1, finding that the P load was 64% less under 0.1 leaching fractions than that of 0.2.
Warsaw et al. (2009a) reported that when irrigation was based on plant daily water use (DWU),
The N and P loss in the effluent was reduced by 59% and 74% under the most conservative
irrigation treatment. Therefore, growers and the surrounding ecosystem could also benefit from
less nutrient leaving production areas by scheduling irrigation based on plant demand.
While scheduling irrigation based on plant DWU could be beneficial, there are certain
aspects that growers need to take into consideration when adopting such practice. The pour
through EC value of the substrate in current study was generally above recommended range 0.2
to 0.5 dS· -1 for container grown woody ornamentals in pine bark substrate fertilized with only
m
a CRF (Southern Nursery Association, 2007). This was a result of salt accumulation from the
fertilizer, however, there was no plant salt damage observed in the current study nor in previous
similar studies (Warsaw et al., 2009a, b). Since woody ornamentals have different salt tolerance
levels (Monk and Wiebe, 1961), container nursery growers that irrigate at zero leaching fraction
should monitor the substrate EC levels to avoid possible salt damage to the plant.

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The DWU, WUE and Kc of ten woody ornamental plants evaluated in this study will allow
nursery growers to group plants with similar water use into appropriate irrigation zone, therefore
conserve water and avoid over-watering or under-watering plants. Additionally, the method used
in this experiment can be applied to identify the DWU and Kc of more woody ornamentals in the
future.

Alternative Containers
The objective of this project was to look for alternative to plastic containers that are suitable
for nursery production. In order to achieve this aim, plant growth, water use and substrate
temperature in alternative containers and plastic containers were evaluated, and the physical
properties and biodegradability of the containers were tested using ASTM standards.
During 2011 and 2012, results of plant growth, water use, substrate temperature and
physical properties of alternative containers and plastic containers was obtained. During 2011
and 2012, plant final growth in all alternative containers was not different to those grown in
plastic containers. Evans and Hensley (2004) found that when irrigated according to plant needs,
the dry shoot weight of impatiens and vinca plants in poultry feather containers were greater than
that grown in peat and plastic containers. The results above indicate that when water supply is
sufficient, plants grown in biodegradable containers have similar or better growth than plants
grown in plastic containers. The mortality rate of Euonymus fortunei grown in Western pulp
(WP) and Kord fiber (Kord) containers was 2% at the end of October, 2011, however, the
mortality rate of E. fortunei grown in WP and Kord containers increased to 52% after being
stored in the hoophouse during winter of November 2011 through May 2012 with no irrigation.

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On the contrary, there were no Buxus x ‘Green Velvet’ lost throughout the experiment. This
indicates that growers could adopt alternative containers without affecting plant growth,
however, growers need to consider substrate moisture availability and plant water stress
tolerance when paper fiber containers are used in climates where winter irrigation is not possible.
In 2011, plants grown in WP and Kord containers used 543.3% and 296.7% more water than
those grown in Plastic containers, which could be explained by higher water vapor transmission
rate (WVTR) from alternative containers than that of Plastic containers (Chapter 2). Similarly,
Evans et al. (2010) found more water was required for geraniums to achieve marketable size in
paper containers than those grown in Plastic containers. They also reported that the rate of water
loss through the wall plays a major role in container water use. These results suggest growers
should consider irrigation budgets and water availability when adopting paper fiber containers.
Plants grown in low WVTR alternative containers, such as the keratin containers, generally
require similar or less water than those grown in plastic containers. The substrate temperature of
all alternative containers was lower than that of Plastic containers. The higher temperature of
substrate in Plastic containers was attributed to more heat absorption by the carbon black
additive used as UV stabilizer. Growers may use alternative containers to replace plastic
containers in the summer to achieve a more stable root zone temperature for the plants.
The physical properties of alternative containers differ from plastic containers according to
their components. All alternative containers had greater compression strength than that of Plastic
containers except Root pouch (RP) containers. Growers may experience transportation difficulty
with RP containers as the containers will easily deform, moreover, the decreased tensile strength
of RP containers after 2 months in the nursery could also result product damage during
transportation. In terms of compostability, WP and Kord containers passed biodegradation tests
119

when ground to a powder form but not in 1x 1 cm pieces. Since we do not have the formula of
the containers from the manufacturer, we could not conclude that WP and Kord containers are
compostable. Alternative containers are often cut into similar sized pieces when being disposed,
and they were not proven to be compostable under this common practice. All containers tested
passed the germination test, showing that the containers had no negative impact on seedling
growth.
The results stated above demonstrate that alternative containers do not have a negative impact
on plant growth when irrigated according to plant needs. However, the growers located in areas
with restricted water use or high water costs should consider alternative containers with low
WVTR such as Keratin containers. Growers should also choose the containers according to their
product commercial shelf life since containers, for example, WP, Kord and RP containers will
show signs of wear after being in the field for 12 month or shorter and, therefore, they are not
suitable for multi-season production.

Future Research
We conducted woody ornamental irrigation management and alternative container studies to
look for more sustainable practices for container nurseries. A container nursery that pursues
sustainable practices could combine the plant DWU based irrigation scheduling with the
adoption of alternative containers to reduce water use and minimize plastic waste environmental
impact.
Since both water and petroleum are valuable resource with increasing global demand,
growers that choose paper pulp based containers or fabric containers, such as Kord and WP
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containers, should balance the benefit of reducing plastic waste against more water use. Greater
irrigation use could result in more runoff effluent and nutrient loss (Warsaw et al, 2009).
Growers may select alternative containers with a smaller or similar water use to that of plastic
containers, such as KR containers, to further reduce irrigation amount and water cost.
Increasing environmental regulations and restrictions faced by nursery operations create the
challenge to growers to adopt sustainable practices while maintaining economic viability. Since
adopting alternative containers in container nursery production could potentially increase water
consumption, future research on nursery production could focus on greater efficiency of
irrigation and fertilization for production using alternative containers. Meanwhile, future
alternative container research should focus on material physical properties such as low WVTR,
high compression and tensile strength, and good water retention ability.

121

LITERATURE CITED

122

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ASTM. 2004. ASTM D6400-04 Standard specification for compostable plastics. ASTM
International, West Conshohocken, PA
ASTM. 2011. ASTM D6868-11 Standard specification for labeling of end items that incorporate
plastics and polymers as coating or additives with paper and other substrates designed to
be aerobically composted in municipal or industrial facilities. ASTM International, West
Conshohocken, PA
Evans, M. R. and D. L. Hensley. 2004. Plant growth in plastic, peat, and processed poultry
feather fiber growing containers. HortScience. 39(5): 1012-1014.
Evans, M. R., M. Taylor and J. Kuehny. 2010. Physical properties of Biocontainers for
greenhouse crops production. Horttechnology, 20 (3), 549-555.
Monk, R. W. and H. H. Wiebe. 1961. Salt tolerance & protoplasmic salt hardiness of various
woody & herbaceous ornamental plants. Plant Physiology. 36(4): 478.
Owen, J. S., S. L. Warren, T. E. Bilderback and J. P. 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.
Schuch, U.K. and D.W. Burger. 1997. Water use and crop coefficients of woody ornamentals in
containers. J. Amer. Soc Hort. Sci. 122(5):727-734
Southern Nursery Association. 2007. Best management practices: Guide for producing nursery
crops. 2nd Ed. Southern Nursery Association, Atlanta, GA.
Warsaw, A. L., R. F. Fernandez, B. M. Cregg and J. A. Andresen. 2009a. Container-grown
ornamental plant growth and water runoff nutrient content and volume under four
irrigation treatments. Production, HortScience. 44(6): 1573–1580.
Warsaw, A. L., R. F. Fernandez, B. M. Cregg and J. A. Andresen. 2009b. Water conservation,
growth, and water use efficiency of container-grown woody ornamentals irrigated based
on daily water use. HortScience. 44(5): 1308-1318.
Yeager, T., J. Million, C. Larsen and B. Stamps. 2010. Florida nursery best management
practices: past, present, and future. HortTechnology. 20(1): 82-88.

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