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NITROGEN FERTILIZATION AND SOIL CULTIVATION
UTILIZING HIGH PRESSURE WATER INJECTION

By

Douglas Edward Karcher

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

MASTER OF SCIENCE

Department of Crop and Soil Sciences

1997

ABSTRACT

NITROGEN FERTILIZATION AND SOIL CULTIVATION UTILIZING HIGH
PRESSURE WATER INJECTION

By

Douglas Edward Karcher

Water injection cultivation (WIC) was introduced in 1990 as a new method of
cultivating turfgrass soils. The Tom HydroJect’, the first WIC unit reaching the market,
uses 20 MPa water bursts cultivating at 15 cm depths while causing minimal surface
disruption. As with many new technologies, indirect WIC applications and complications
merit investigation. Studies were initiated to determine the effectiveness of applying
nitrogen fertilizer via WIC and examine the indirect benefits and detriments of WIC
technology on putting green and fairway turf. Injecting nitrogen resulted in several
beneficial turfgrass responses. Poa annua encroachment into an Agrostis palustris turf
did not differ significantly between turf receiving WIC and hollow tine cultivation after
three years of treatments. Frequent WIC of a turf containing a sand topdressing layer
overlying a finer-textured soil resulted in mixing of the layers at the interface, but finer-
textured soil was not blasted to the turfgrass surface.

To my parents, Harold and Joyce, whose continual love, guidance, and support have
made my graduate education possible.

iii

ACKNOWLEDGMENTS

I extend my deepest gratitude to Dr. Paul E. Rieke, my major advisor and research
committee chairman. His sincere interest in my graduate experience and unceasing
integrity are lessons that go beyond turfgrass soil science. These lessons will be with me
always in my future endeavors. A special thanks also to Dr. John N. Rogers III and Dr.
Joseph M. Vargas, for their time and contributions while participating on my research
committee.

This research project would not have been possible without support from the Toro
Company of Minneapolis, Minnesota. Their provisions of annual opportunities to
collaborate with Toro personnel and researchers abroad was a display of professionalism
that was much appreciated. Interaction with Dr. Jim R. Watson was always both
educational and motivational. I especially enjoyed working closely with HydroJect
engineers Mr. Marc Anderson, Mr. Robert Corner, and Mr. Dana Lonn. They almost
accomplished the feat of making me mechanically inclined.

Finally, I would like to thank my fellow graduate students and for their friendship
and support. Thank you Thom Nikolai for teaching me virtually every field research
technique I know, John Sorochan for keeping things anything but dull at the research
center, and Wendy Matig for your hours of unpaid assistance in the lab.

Those deserving of thanks who are not listed are certainly not forgotten and to
extend gratitude to everyone who enriched my graduate experience would be a thesis

itself.

iv

TABLE OF CONTENTS

List of Tables
Chapter One: Nitrogen Fertilization of Turfgrass Using High Pressure

Water Injection

Abstract

Introduction

Literature Review
Materials and Methods
Results and Discussion
Bibliography

Chapter Two: Water Injection Cultivation of a Sand Topdressed Putting Green

Abstract

Introduction

Literature Review
Materials and Methods
Results and Discussion
Bibliography

Chapter Three: Cultivation Effects on Poa annua Encroachment into a

Creeping Bentgrass Putting Green

Abstract

Introduction

Literature Review
Materials and Methods
Results and Discussion
Bibliography

65
65

68
69
72
89

Table

1.1.

1.2.

1.3.

1.4.

1.5. .

1.6.

1.7.

1.8.

1.9.

1.10.

1.11.

1.12.

1.13.

1.14.

LIST OF TABLES

Effect of nitrogen application method and rate on clipping yields of
a Poa annua fairway. 1994.

Effect of nitrogen application method and rate on clipping yields of
a Poa annua fairway. 1995.

Effect of nitrogen application method and rate on clipping yields of
an Agrostis palustris putting green. 1994.

Effect of nitrogen application method and rate on clipping yields of
an Agrostis palustris putting green. 1995.

Effect of nitrogen application method and rate on nitrogen content
of a Poa annua fairway. 1994 and 1995.

Effect of nitrogen application method and rate on nitrogen content
of an Agrostis palustris putting green. 1994 and 1995.

Effect of nitrogen application method and rate on quality of a Poa
annua fairway. 1994.

Effect of nitrogen application method and rate on quality of a Poa
annua fairway. 1995.

Effect of nitrogen application method and rate on quality of an
Agrostis palustris putting green. 1994.

Effect of nitrogen application method and rate on quality of an
Agrostis palustrr's putting green. 1995.

Effect of nitrogen application method and rate on color of a Poa
annua fairway. 1994.

Effect of nitrogen application method and rate on color of a Poa
annua fairway. 1995.

Effect of nitrogen application method and rate on color of an
Agrostis palustris putting green. 1994.

Effect of nitrogen application method and rate on color of an
Agrostis palustris putting green. 1995.

vi

10

12

13

14

16

18

19

20

21

23

24

26

27

1.15.

2.1.

2.2.

2.3.

2.4.

2.5.

2.6.

2.7.

2.8.

2.9.

2.10.

2.11.

3.1.

3.2

3.3.

3.4.

3.5.

3.6.

Effect of nitrogen application method and rate on wilting. 1994 and
1 995 .

Effect of cultivation treatment on the mixing of a sand topdressing
layer with underlying native soil. Samples collected 9/18/95.

Effect of cultivation treatment on the mixing of a sand topdressing
layer with underlying native soil. Samples collected 9/15/96.

Effect of cultivation treatment on quality of a sand topdressed putting
green.

Effect of cultivation treatment on moisture stress symptoms of a sand
topdressed putting green.

Effect of cultivation treatment on root weight density of a sand
topdressed putting green. 1996.

Effect of cultivation treatment on ball roll distance of a sand
topdressed putting green. 1994.

Effect of cultivation treatment on ball roll distance of a sand
topdressed putting green. 1995.

Effect of cultivation treatment on ball roll distance of a sand
topdressed putting green. 1996.

Effect of cultivation treatment on physical soil properties of a sand
topdressed putting green. 1995.

Effect of cultivation treatment on physical soil properties of a sand
topdressed putting green. 1996.

Effect of water injection cultivation on the mixing of a sand
topdressing layer with the underlying native soil.

Effects of cultivation treatment on Poa annua encroachment into a
creeping bentgrass putting green.

Effects of cultivation on quality of a creeping bentgrass putting
green. 1994.

Effects of cultivation on quality of a creeping bentgrass puffing
green. 1995.

Effects of cultivation on quality of a creeping bentgrass putting
green. 1996.

Effect of cultivation on ball roll distance of a creeping bentgrass
putting green. 1994.

Effect of cultivation on ball roll distance of a creeping bentgrass
putting green. 1995.

vii

28

45

46

49

51

52

53

54

55

57

58

60

73

74

76

77

79

80

3.7.

3.8.

3.9.

3.10.

Effect of cultivation on ball roll distance of a creeping bentgrass
putting green. 1996.

Effect of cultivation treatment on physical soil properties of a
creeping bentgrass putting green. 1995.

Effect of cultivation treatment on physical soil properties of a
creeping bentgrass putting green. 1996.

Effect of cultivation treatment on earthworm castings and biomass on
a creeping bentgrass putting green.

viii

81

84

85

86

CHAPTER ONE

Nitrogen Fertilization of Turfgrass Using
High Pressure Water Injection Cultivation.

ABSTRACT

Subsurface placement of nitrogen fertilizers have increased yields in the food and
forage industry. Minimal past research has evaluated subsurface placement of nitrogen
fertilizers in turfgrass, primarily due to the unavailability of equipment to apply materials
subsurfacely without causing considerable surface disruption. The introduction of water
injection cultivation in the early 1990’s made subsurface placement of soluble materials
possible. The HydroJect 3000’ uses a 20 MPa blast of water to cultivate turfgrass areas
while causing minimal surface disruption. Studies were initiated in 1994 to examine the
effects of injecting nitrogen with the HydroJect into an annual bluegrass (Poa annua L.
reptans) fairway and a ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) putting
green. Treatments included three rates of urea (fairway study- 1.2, 2.4, and, 3.6 g N rn'2
application"; putting green study-- 1.2, 3.4, and 4.8 g N rn‘2 application") either injected
or surface applied and were replicated four times in each study. Nitrogen was applied on
five dates during the 1994 growing season at approximately 24 day intervals. Plots
injected with urea had significantly higher clipping yields, nitrogen content in leaf tissue,
and color ratings than plots receiving surface applications on several evaluation dates.
These differences could have been caused by ammonia volatilization from surface

applications, even though plots were irrigated shortly after application. This theory was

tested by repeating the studies in 1995 using ammonium nitrate as the nitrogen source.
Ammonium nitrate was applied on six dates during the 1995 growing season. Results
fi'om the 1995 study were very similar to those recorded the previous year. Therefore, it
is likely that factors other than ammonia volatilization increase nitrogen efficiency when
applications are made via injection. Although injected plots had darker green color
ratings, they exhibited a striping pattern caused by the spacing of the injection nozzles
(7.5 cm) that reduced turf quality ratings. Striping lasted for approximately 10 days
following application and was less noticeable following succesive applications. During
both years, plots injected with nitrogen were less susceptible to wilt stress than those

receiving surface applications.

Introduction

Subsurface applications of nitrogen have proven to increase plant nitrogen use
efficiency in the food and forage crop industries. More efficient use of nitrogen through
better application methods has conserved energy and resources required for nitrogen
fertilizer synthesis. Rapid suburban growth and golf course construction has resulted in
increased nitrogen fertilizer use in the turfgrass industry during recent decades. More
efficient application methods, and the subsequent conservation of nitrogen in the turfgrass
industry, would save energy and reduce risk of environmental contamination.

Early agricultural fertilization was accomplished through broadcast applications.
Concerns of inefficient fertilizer use from broadcasting, especially nitrogen losses,
initiated extensive research efforts to study the efi‘ects of subsurface fertilizer placement
on plant growth. This research almost exclusively focused on food and forage production
with little literature available on subsurface fertilizer placement in turfgrass. The lack of
fertilizer placement research in turfgrass is partly the result of insufficient means to place
fertilizer below the soil surface in an established turfgrass stand. Equipment used for
subsurface placement of fertilizer in food and forage production would result in
considerable surface disruption on an established turfgrass stand. The recent
development of high pressure water injection as a turfgrass cultivation practice has made
subsurface placement of materials a possibility. The Toro HydroJect 3000“ uses a 20
MPa blast to inject water 10 to 20 cm below the soil surface while causing minimal
surface disruption (Murphy, 1994). Subsurface turfgrass fertilization is made possible by
dissolving fertilizer material and pumping it through the HydroJect. Previous research
conducted at Michigan State University demonstrated that the injection of dissolved

nutrients with the HydroJect was an effective application method (Miller, 1994).

The objective of this research was to determine if the application of nitrogen by
injection is an effective means of fertilizing turfgrass. A HydroJect 30000 was used to
inject nitrogen into an annual bluegrass (Poa annua L. reptans) fairway and a ‘Penncross’

creeping bentgrass (Agrosris palustris Huds.)

Literature Review

Past research on subsurface fertilization has focused heavily on food and forage
crop production. Mengel et al., in 1982, found that injecting nitrogen carriers below the
soil surface with commercial anhydrous knife equipment resulted in significantly higher
grain yields for conventional and no-till corn (Zea mays L.) compared to surface
applications. Nitrogen content of grain and leaves was consistently higher with injected
treatments than surface applications. Similar results were obtained by Stecker et al., in
1993, comparing the effects of knifing and broadcasting urea ammonium nitrate on no-till
corn. They found corn grain yields increased by 5 to 40% with subsurface nitrogen
placement. Nitrogen content of grain and leaves increased significantly when nitrogen
was injected. Comparable results have been obtained on no-till corn when nitrogen was
injected with pressurized nozzles similar to those used by the HydroJect (Howard and
Tyler, 1989). Increased yields, leaf nitrogen concentration, and nitrogen uptake by the
plant were obtained by injecting nitrogen rather than surface banding or broadcasting.
These results were attributed to a decreased potential for volatilization and/or
immobilization in the soil of nitrogen when injected. Subsurface placement of nitrogen
improved the production of no-till winter wheat (Triticum aestivum L.) (Fowler and
Brydon, 1989) and brome grass (Bromus inermis, Leyss) (Ogus and Fox, 1970).

Subsurface banding of nitrogen in a tall fescue (F estuca amndinacea Schreb)
forage crop, a cool season perennial species often utilized as a turfgrass, improved

nitrogen uptake, increased forage yields, and increased leaf nitrogen content compared to

surface applications (Lamond and Meyer, 1983). Raczkowski and Kissel (1989) obtained
similar results and hypothesized that treatment differences resulted fiom atmospheric
losses of nitrogen with the surface application. Both of these studies required non-
commercial application equipment to band nitrogen into established sod.

Most literature available on fertilizer placement in ttn'fgrass concerns turfgrass
establishment, i.e. fertilizer placement effects on seed germination or sod establishment
(Jackson and Burton, 1962; King and Skogley, 1969; King and Beard, 1972, Peacock and
Dudeck, 1982). This work has shown minimal differences in ttn'fgrass establishment
with regard to fertilizer placement.

When the HydroJect became available as a turfgrass management tool in 1990,
research concerning subsurface placement of fertilizer began to focus on established
turfgrass systems. Miller (1994) showed that the HydroJect could be utilized to
effectively inject P20, and K20. Murphy and Rieke (1992) found that nitrogen injection
in the late fall resulted in a more uniform green up the following spring when compared
to surface applications, and that nitrogen recovery was 34% greater with injection. Miller
and Rieke (1994) discovered that turfgrass injected with nitrogen had significantly higher
clipping yields than plots receiving surface applications. Murphy and Zaurov observed,
in a 1994 study, that greenhouse turfgrass plots receiving subsurface nitrogen injections
demonstrated higher clipping yields, greater root mass, higher nitrogen accumulation in
plant tissues, and higher water use rate efficiency than turfgrass receiving surface

applications of nitrogen.
Materials and Methods
The nitrogen injection studies were initiated in June 1994, at the Hancock

Turfgrass Research Center on the campus of Michigan State University to determine the

effects of injecting nitrogen with the HydroJect“ on fairway and putting green turfs.

Treatments included three rates of nitrogen, either injected or surface applied. The
nitrogen source used for all treatments was urea in 1994 and ammonium nitrate in 1995.
No supplemental fertilization was applied. Treatment differences observed in 1994 may
have been the result of ammonia volatilization from surface applied urea Ammonium
nitrate was used as the nitrogen source in 1995 to minimize treatment differences
possibly resulting from ammonia volatilization (Bandel et al., 1980). Nitrogen injections
were made with a HydroJect 3000 provided by the Tom Co. of Minneapolis. A nitrogen
solution was pumped from a holding tank to the intake line of the HydroJect and
subsequently injected into the soil. Injections were made with 20 MPa blasts that reached
average depths of 12 cm. The HydroJect was calibrated for nitrogen injection prior to
treatments. Surface applications were made using a C02 powered sprayer designed
specifically for small plot applications. Approximately 0.5 cm of water was applied to all
plots immediately following nitrogen fertilization.

The three nitrogen rates for the fairway study were 1.2, 2.4, and 3.6 g rn’2 per
application. A double rate was used for a late fall application on Nov. 8, 1994. Nitrogen
was applied on Jun. 27, Aug. 9, Sep. 1, Sep. 30, and Nov. 8 in 1994; and May 12, Jun. 6,
Jun. 30, Jul. 25, Aug. 18 and Sep. 12 in 1995. During each growing season, a total of 7.2,
14.4, and 21.6 g N m2 was applied for the low, medium, and high nitrogen rate
treatments. The fairway study was conducted on an 11-year old annual bluegrass turf
established on a fine-loamy, mixed, mesic Typic Hapludalf (67.8% sand, 19.1% silt, 13%
clay). The experimental area was mowed at 1.25 cm and maintained under typical
fairway management practices. Mowing was performed three times per week during the
majority of the growing season. Irrigation was applied daily unless the turf received
sufficient water from precipitation. Pesticides were applied on a curative basis and no
supplemental fertilization was applied during the study.

The three nitrogen rates for the putting green study were 1.2, 3.0, and 4.8 g m'2 per

application. A double rate was used for a late fall application on Nov. 8, 1994. Nitrogen

was applied on Jun. 27, Aug. 9, Sep. 1, Sep. 30, and Nov. 8 in 1994; and May 12, Jun. 6,
Jun. 30, Jul. 25, Aug. 18 and Sep. 12 in 1995. During each growing season a total of 7.2,
18.0, and 28.8 g N m‘2 was applied for the low, medium, and high nitrogen rate
treatments. The putting green study was conducted on a three-year old ‘Penncross’
creeping bentgrass green established on a modified sand (95.1% sand, 0.4% silt, 4.5%
clay) meeting USGA specifications. The experimental area was mowed at 0.5 cm and
maintained under typical putting green management practices. Mowing was performed
five times per week during the majority of the growing season. Irrigation was applied
daily unless the turf received sufficient water from precipitation. Pesticides were applied
on a curative basis and no supplemental fertilization was applied during the study.

Clippings were collected by mowing one pass lengthwise on each plot, an area
approximately 1.8 m2, with a walking reel mower at two week intervals. Clippings were
harvested on Jul. 14, Jul. 29, Aug. 15, Aug. 29, Sep. 12, and Oct. 7 in 1994; and May 15,
May 30, Jun. 12, Jun. 29, Jul. 10, Jul. 24, Aug. 14, Sep. 7, and Oct. 19 in 1995. Clippings
were collected following 3 to 5 days of growth. Clippings were dried at 60°C and
weighed to determine dry matter yield. Clippings were analyzed for nitrogen content on
a monthly basis using micro Kjeldahl techniques: Aug. 15 and Sep. 12, 1994; and May
15, Jun. 26, Aug. 7, Sep. 7, and Oct. 19, 1995.

Turfgrass quality and color ratings were taken approximately every 2 weeks
throughout the growing season. Quality ratings were based on turfgrass uniformity,
density, and color. Plots were ranked on a scale of l to 9, with 1 being dead turf, 6
minimum acceptable quality, and 9 uniform, dense, dark green turf.. A similar scale was
used for color ratings with 1 being brown turf, 6 acceptable color, and 9 dark green turf.
Quality and color ratings were taken on Jul. 14, Jul. 29, Aug. 15, Aug. 29, Sep. 12, Sep.
26, Oct. 10, Oct. 25, and Nov. 8 in 1994; and Apr. 21, May 8, May 19, Jun. 2, Jun. 16,
Jun. 29, Jul. 16, Aug. 9, Aug. 23, and Sep. 17 in 1995.

Wilt ratings were taken when noticeable drying had occurred over the
experimental area. Irrigation was turned off to exacerbate moisture stress symptoms
during periods of high evapotranspiration. A scale fi'om 1 to 9 was used with 1 being no
wilt, 6 moderate wilt, and 9 severe wilt. Due to an unusually wet summer, plots exhibited
sufficient wilt for rating only on the fairway study on Sep. 14 in 1994. Wilt ratings were
taken on Jul. 12 and Sep. 3 on fairway plots, and Sep. 25 on putting green plots in 1995.

A randomized complete block design was used as the error control design.
Treatments were replicated four times. A two-factor analysis of variance was calculated
for all data to indicate differences in application methods, differences in nitrogen levels,
and levels of interaction between the two factors. Application method means were
determined significantly different at probabilities s 0.05. Nitrogen rate means were
separated using Fisher’s protected least significant difference procedtn'e at the 0.05 level
of probability. Differences between application method means and among nitrogen rate
means are reported with 95 % confidence intervals for treatment mean differences
(F reund and Wilson, 1993). There were no factor interactions when the seasonal data

was averaged, so only main effects are reported.

Results and Discussion

Clipping yields

Clipping yield data for the fairway study are summarized in Tables 1.1 and 1.2.
On average, plots injected with nitrogen had mean annual clipping yields 1.3 :1: 1.9 g m“2
greater than plots receiving surface applications in 1994; and 1.7 :1: 1.0 g rn‘2 greater than
plots receiving surface applications in 1995. Injected plots had significantly greater (P <
0.05) clipping yields than surface application on one of six days clippings were collected
in 1994 and three of nine dates clippings were collected in 1995. Surface applied plots
had significantly greater (P < 0.05) yields than injected plots only on Sep. 7, 1995. Plots

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receiving the high nitrogen rate had mean annual clipping yields 3.0 :t 2.3 g m'2 greater
than the medium nitrogen rate and 4.7 i 2.3 g m’2 greater than the low nitrogen rate in
1994; 2.1 :l: 1.3 g m'2 greater than the medium nitrogen rate and 5.0 :t 1.3 g m’2 greater
than the low nitrogen rate in 1995. There were significant differences in clipping yields
(P < 0.05) among nitrogen rate treatments on three of six days clippings were collected in
1994 and seven of nine dates clippings were collected in 1995. ‘

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1.4. On average, plots injected with nitrogen had mean annual clipping yields 3.0 :t 0.9 g
m’2 greater than plots receiving surface applications in 1994; and 3.0 :t 2.1 g m'2 greater
than plots receiving surface applications in 1995. Injected plots had significantly greater
clipping yields (P S 0.05) than surface application on four of six dates clippings were
collected in 1994 and five of nine dates clippings were collected in 1995. Plots
receiving the high nitrogen rate had mean annual clipping yields 1.6 :l: 1.0 g m’2 greater
than the medium nitrogen rate and 3.4 :t: 1.0 g m“2 greater than the low nitrogen rate in
1994; and 3.8 :l: 2.6 g m‘2 greater than the medium nitrogen rate and 13.0 :I: 2.6 g m’2
greater than the low nitrogen rate in 1995. There were significant differences in clipping
yields (P S 0.05) among nitrogen rate treatments on four of six dates clippings were
collected in 1994, and all nine dates clippings were collected in 1995.
Nitrogen content

Nitrogen content data for the fairway study are summarized in Table 1.5. The
mean annual nitrogen content in plant tissue for plots injected with nitrogen was 0.6 :t: 0.3
g N 100 g" greater than plots receiving surface applications in 1994; and 0.1 :l: 0.2 g N
100 g" greater than plots receiving surface applications in 1995. Turf injected with
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dates clippings were analyzed in 1994 and only one of five dates that clippings were
analyzed in 1995. Turf receiving the high nitrogen rate had mean annual nitrogen
contents 0.4 i 0.4 g N 100 g’1 greater than plots receiving the medium nitrogen rate and

12

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15

0.8 :t 0.4 g N 100 g’I greater than plots receiving the low nitrogen rate in 1994; and 0.4 i
0.3 g N 100 g“ greater than plots receiving the medium nitrogen rate and 0.6 1: 0.3 g N
100 g‘1 greater than plots receiving the low nitrogen rate in 1995. There were significant
differences in nitrogen content (P S 0.05) among nitrogen rate treatments on both days
clippings were analyzed in 1994 and three of five dates that clippings were analyzed in

1 995.

Nitrogen content data for the putting green study are summarized in Table 1.6.

On average, plots injected with nitrogen had tissue nitrogen content 0.5 :l: 0.4 g N 100 g’l
greater than plots receiving surface applications in 1994; and 0.3 :1: 0.2 g N 100 g'1 greater
than plots receiving surface applications in 1995. Injected plots had significantly higher
nitrogen contents (P S 0.05) in plant tissues on both dates clippings were analyzed in
1994 and two of five dates in 1995. Plots receiving the high nitrogen rate had mean
annual nitrogen contents 0.7 :t 0.4 g N 100 g" greater than plots receiving the medium
nitrogen rate and 0.9 :l: 0.4 g N 100 g'1 greater than plots receiving the low nitrogen rate in
1994; and 0.3 i 0.2 g N 100 g'1 greater than plots receiving the medium nitrogen rate and
0.6 :l: 0.2 g N 100 g’1 greater than plots receiving the low nitrogen rate. There were
significant differences in nitrogen content (P S 0.05) among nitrogen rate treatments on
both dates clippings were analyzed in 1994 and four of five dates in 1995.

Nitrogen content in plant tissues ranged from 1.9 g N 100 g" on turf fiom surface
applied plots in the fairway study on Aug. 15, 1994 to 5.1 g N 100 g'l on turf from the
high nitrogen rate plots in the fairway study on Aug. 7, 1995. This nitrogen content range
is similar to ranges reported from previous studies involving nitrogen fertilization of turf.
Miller (1994) reported nitrogen contents in plant tissues ranging from 1.6 g N 100 g'l to
4.1 g N 100 g'1 in creeping bentgrass clippings receiving from 2.4 g N m’2 to 4.8 g N m‘z,
either injected or surface applied. Munsell and Brown (1939) reported nitrogen contents
in plant tissues ranging from 2.0 g N 100 g’1 to 4.5 g N 100 g" in Kentucky bluegrass
clippings receiving from 3.4 g N m’2 to 6.8 g N m’z.

16

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17

Quality ratings

Quality rating data for the fairway study are summarized in Tables 1.7 and 1.8.
On average, plots injected with nitrogen had a mean annual quality rating of 0.2 :I: 0.2
point higher than plots receiving surface applications in 1994; and 0.2 :l: 0.3 point higher
than plots receiving surface applications in 1995. Injected plots had significantly higher
quality ratings (P S 0.05) on three of nine days ratings were taken in 1994 and five of ten
days ratings were taken in 1995. Plots receiving surface applications ranked significantly
higher (P S 0.05) than injected plots only on the Apr. 21, 1995 rating. Plots receiving the
high nitrogen rate had mean annual quality ratings 0.4 :l: 0.3 point higher than the plots
receiving the medium nitrogen rate and 1.0 i 0.3 point higher than plots receiving the low
nitrogen rate in 1994; and 0.9 :l: 0.3 point higher than plots receiving the medium nitrogen
rate and 2.0 i 0.3 points higher than plots receiving the low nitrogen rate in 1995. There
were significant differences in quality (P S 0.05) among nitrogen rate treatments seven of
nine days ratings were taken in 1994 and on all ten days ratings were taken in 1995.

Quality rating data for the putting green study are summarized in Tables 1.9 and
1.10. On average, plots injected with nitrogen had a mean annual quality rating of 1.0 i
0.5 point higher than plots receiving surface applications in 1994; and 0.1 :t 0.2 point
higher than plots receiving surface applications in 1995. Injected plots rated significantly
higher in quality (P S 0.05) than plots receiving surface applications seven of nine dates
ratings were taken in 1994, and only on June 29, 1995. Plots receiving surface
application did not rank significantly higher in quality (P S 0.05) on any dates ratings
were taken. Plots receiving the high nitrogen rate had mean annual quality ratings 0.7 :1:
0.7 point higher than plots receiving the medium nitrogen rate and 2.0 :t 0.7 points higher
than plots receiving the low nitrogen rate in 1994; and 0.5 i 0.3 point higher than plots
receiving the medium nitrogen rate and 2.0 i 0.3 points higher than plots receiving the

low nitrogen rate in 1995. There were significant differences in quality (P S 0.05) among

18

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19

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21

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22

nitrogen rate treatments on seven of nine dates ratings were taken in 1994, and nine of ten
days ratings were taken in 1995.

Turf injected with nitrogen exhibited dark green stripes following the nozzle
pattern of the HydroJect (7.5 cm wide), which lowered turf quality ratings. The striping
appeared most noticeably at lower mowing heights and when the turf was nitrogen
starved prior to fertilization. The injection stripes appeared approximately 3 days
following treatment and usually faded within a week to 10 days. Striping was less
apparant following successive nitrogen applications and faded in a shorter period of time.
Turf managers may be able to apply nitrogen at half rates in two opposite directions to
avoid dark green stripes in the turf.

Color ratings

Average color rating values were determined for striped turf resulting from
nitrogen injection by rating the plots from a distance where the turf appeared as a uniform
color. Color rating data for the fairway study are summarized in Tables 1.11 and 1.12.
An average color rating value was determined for striped turf resulting from nitrogen
injection by rating the plots fi-om a distance where the turf appeared as a single color. On
average, plots injected with nitrogen had a mean annual color rating of 0.5 :1: 0.2 point
higher than plots receiving surface application in 1994; and 0.2 :1: 0.2 point higher than
plots receiving surface applications in 1995. Injected plots had significantly higher color
ratings (P S 0.05) on four of nine dates ratings were taken in 1994 and five of ten days
that ratings were taken in 1995. Plots receiving surface applications ranked significantly
higher in color (P S 0.05) than injected plots on the August 9, 1995 rating. Plots
receiving the high nitrogen rate had mean annual color ratings 0.5 :t 0.3 point higher than
plots receiving the medium nitrogen rate and 0.9 :t: 0.3 point higher than plots receiving
the low nitrogen rate in 1994; and 0.8 :1: 0.2 point higher than plots receiving the medium
nitrogen and 1.6 :t 0.2 points higher than plots receiving the low nitrogen rate in 1995.

There were significant differences in color (P S 0.05) among nitrogen rate treatments

23

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24

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25

eight of nine dates ratings were taken in 1994 and on all ten days that ratings were taken
in 1995.

Color rating data for the putting green study are summarized in Tables 1.13 and
1.14. On average, plots injected with nitrogen had a mean annual color rating of 1.3 :t
0.5 points higher than plots receiving surface application in 1994; and 0.4 :l: 0.3 point
higher than plots receiving surface applications in 1995. Injected plots had significantly
higher color ratings (P S 0.05) on all nine dates ratings were taken in 1994 and six of ten
days that ratings were taken in 1995. Plots receiving the high nitrogen rate had mean
annual color ratings 0.6 i 0.7 point higher than plots receiving the medium nitrogen rate
and 1.2 :l: 0.7 points higher than plots receiving the low nitrogen rate in 1994; and 0.6 :I:
0.3 point higher than plots receiving the medium nitrogen and 2.0 :t 0.3 points higher
than plots receiving the low nitrogen rate in 1995. There were significant difl‘erences in
color (P S 0.05) among nitrogen rate treatments seven of nine dates ratings were taken in
1994 and on all ten days that ratings were taken in 1995.
Wilt ratings

Wilt ratings were taken on Sep. 14, 1994, Jul. 12, 1995, and Sep. 3, 1995 on the
fairway study and Sep. 25, 1995 on the putting green study when noticeable drying had
occurred over the experimental area. Data fi'om these ratings are summarized in Table
1.15. Plots receiving surface applications of nitrogen had significantly more wilt severity
(P S 0.05) than injected plots on all dates that ratings were taken for both studies.

Plots in the fairway study receiving surface applications of nitrogen ranked 2.8 :l:
0.7 points higher in wilt severity on Sep. 14, 1994 than plots receiving injected nitrogen.
Plots receiving the medium nitrogen rate ranked 1.2 :t 0.9 points lower in wilt severity
than plots receiving the high nitrogen rate and 1.0 :t 0.9 point lower in wilt severity than
plots receiving the low nitrogen rate. The low and high nitrogen rates were not

significantly different in wilt severity (P s 0.05).

26

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27

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29

Plots in the fairway study receiving surface applications of nitrogen ranked 3.7 i:
0.9 points higher in wilt severity on Jul. 12, 1995 than plots receiving injected nitrogen.
There were no significant differences in wilt severity among nitrogen rate treatments.
There was evidence of an interaction in wilt severity (P = 0.08) between method of
application and nitrogen rate. Plots receiving surface applications of nitrogen increased
in wilt severity with increasing nitrogen rate. Injected plots did not exhibit this trend.

Plots in the fairway study receiving surface applications of nitrogen ranked 1.8 :t:
0.8 points higher in wilt severity than plots receiving injected nitrogen on Sep. 3, 1995.
Plots receiving the high rate of nitrogen ranked 2.0 i 1.0 points higher in wilt severity
than plots receiving the medium rate of nitrogen and 2.8 :I: 1.0 points higher in wilt
severity than plots receiving the low nitrogen rate. There was a significant interaction in
wilt severity (P S 0.05) between method of application and nitrogen rate. Plots receiving
surface applications of nitrogen increased greatly in wilt severity with increasing nitrogen
rate. Injected plots did not exhibit this trend.

Putting green plots receiving surface applications of nitrogen ranked 0.9 :l: 0.9
point higher in wilt severity than plots injected with nitrogen on Sep. 25, 1995. There
were no significant differences in wilt severity among nitrogen rate treatments, nor was
there any evidence of interaction between application method and nitrogen rate on the
putting green study.

Differences in wilt severity between nitrogen application treatments may be the
result of a deeper active root system for turf that is injected with nitrogen, although roots
were not measured in this study. Fox et. al, (1953) found that deeper rooting of Kentucky
bluegrass occurred in a silt loam soil when a favorable supply of nutrients was present at
all depths in the profile. Deep placement of nitrogen in a coarse textured soil has resulted
in more extensive root proliferation and enhanced sub-soil water utilization by wheat
(Sharma and Chaundry, 1984).

30

Increases in moisture stress symptoms with increasing rates of surface applied
nitrogen has been reported in several studies. Rieke and McElroy (1986) reported more
wilting on creeping bentgrass putting green turf on plots receiving high nitrogen rates
during summer months. Watschke and Waddington (1975) reported that ‘Merion’
Kentucky bluegrass wilted quicker and recovered slower as nitrogen rates were increased.
Turf growing in nitrogen fertile soils tends to develop shoots at the expense of roots,
which decreases the ability to extract moisture fiom lower soil depths. Increased leaf
canopy is also associated with turf receiving high nitrogen rates. Turf transpiration rates
increase with increasing leaf canopy on a per area basis. Consequently, turf receiving
high amounts of nitrogen depletes soil moisture and exhibits moisture stress symptoms
more rapidly than unfertilized turf. Significant nitrogen rate x application method
interactions on the fairway study were the result of nitrogen rate not afl‘ecting moisture
stress symptoms on turf injected with nitrogen. This turf may not exhibit increased
moisture stress typically associated with high nitrogen rates because of more effective
water uptake from lower soil depths. Enhanced water uptake by turf injected with
nitrogen was likely the result of a more active root system at lower depths in the soil
profile. Root system enhancement was probably caused by higher nitrogen
concentrations at lower soil depths (Fox et. al, 1953; Sharma and Chaundry, 1984) and/or
increased macropores at lower soil depths from the cultivation action of the injection
equipment (Murphy and Rieke, 1994).

Summary

On the majority of dates turf was evaluated, the nitrogen injection treatment
significantly increased clipping yields and quality ratings in the putting green study,
significantly decreased moisture stress symptoms in the fairway study, and significantly
increased plant tissue nitrogen content and turf color ratings in both studies during the
1994 growing season when compared to surface applications. These results suggest that
turf used injected urea more efficiently than surface applied urea. The increased

31

efliciency with injected urea could have been the result of decreased atmospheric losses
of nitrogen due to ammonia volatilization. Bowman and Paul (1990) found that 11.6 %
of urea applied to the thatch and surface soil of a Kentucky bluegrass turf was lost to
ammonia volatilization. Significant ammonia volatilization is possible, even when 2.5
cm of irrigation is applied to the turf immediately following nitrogen application
(Raczkowski and Kissel, 1989). Ammonium nitrate, which is much less susceptible to
volatilization, was used as the nitrogen source in 1995 to verify if treatment differences in
1994 resulted solely from ammonia volatilization of urea. In 1995, the nitrogen injection
treatment significant increased the plant tissue nitrogen content and color ratings in the
putting green study, and significantly increased clipping yields and decreased moisture
stress symptoms in both studies.

Factors other than ammonia volatilization are probably involved in increasing
nitrogen use efficiency of turfgrass injected with nitrogen compared to surface
application. There were no check plots (surface applied nitrogen plus water injection
cultivation) in these studies to separate the efi‘ects of nitrogen placement and water
injection cultivation. Positive turfgrass responses resulting from subsurface nitrogen
injection may be partially attributed to changes in soil physical properties resulting from
water injection cultivation. An increase in macropore space from nitrogen applied by
water injection cultivation may reduce denitrification losses compared to turf receiving
surface applied nitrogen. Mancino et. al, (1988) reported increasing denitrification losses
from a ‘Baron’ Kentucky bluegrass turf as air filled pores decreased.

Immobilization by soil microbes and/or localized denitrification may decrease as a
result of placing nitrogen below the soil surface, but it is not conclusive from these
studies. Another possible explanation of treatment differences is that turf used surface
applied nitrogen in a quick burst of growth shortly following application and became
nitrogen starved for a longer period of time prior to subsequent application compared to
turf injected with nitrogen. Bowman, et a1. (1990) found that all of the nitrogen that was

32

surface applied to a Kentucky bluegrass turf was depleted from the soil within 48 hours.
Rapid depletion of nitrogen was attributed to rapid absorption by turf with high root
length densities. Surface applied nitrogen is absorbed rapidly when turf has high root
length density, representing both a large absorbing surface and a very small mean
distance between roots. The uptake of injected nitrogen may be somewhat slower since
the nitrogen is localized in pockets not accessible to the entire turf root system and where
root length densities are lower than those immediately beneath the surface.
Measurements of nitrogen uptake with respect to time following applications were not
evaluated in this study.

Nutrient application using water injection cultivation equipment will benefit
compacted turfgrass areas, especially putting greens, by improving soil physical
properties. High pressure water injection cultivation has been shown to improve bulk
density, porosity, and saturated hydraulic conductivity (Murphy and Rieke, 1994).
Furthermore, subsurface injection of nitrogen may allow turfgrass managers to use less
expensive nitrogen sources while gaining several benefits typically associated with more
expensive slow release nitrogen sources. Turfgrass injected with nitrogen seemed to have
a longer response period, remaining darker in color than surface applications prior to
subsequent nitrogen applications. The turfgrass manager could apply nitrogen less
frequently when implementing subsurface injections. Nitrogen use efficiency should
increase since excess uptake is likely reduced with subsurface nutrient placement. The
potential for foliar burn normally associated with soluble nitrogen sources, which is
intensified by very dense turf on putting greens, would be virtually eliminated by
subsurface nutrient placement.

Subsurface nitrogen applications would be most effective on high maintenance
turf areas such as golf course putting greens. Striping fi'om the nozzle pattern could be
reduced by alternating injection directions each application, injecting in two directions

per application at a larger nozzle spacing, or using injection nozzles with a more

33

dispersed spray pattern. These results indicate that turfgrass mangers could reduce total
nitrogen inputs and irrigation requirements through subsurface injections of nitrogen.
These properties of subsurface nitrogen application may prove to be extremely benefical
as increased environmental awareness and water use restrictions will require managers to

maintain quality turf with fewer inputs.

BIBLIOGRAPHY

Bandel, V. A., S. Dzienia, and G. Stanford. 1980. Comparison of N fertilizers for no-till
corn. Agron. J. 72:337-341.

Bowman, D. C., and J. L. Paul. 1990. Volatilization and rapid depletion of urea spray-
applied to Kentucky bluegrass turf. J. Plant Nutr. 13:1335-1344.

Fowler, D. B., and J. Brydon. 1989. No-till winter wheat production on the Canadian
prairies: placement of urea and ammonium nitrate fertilizers. Agron. J. 81:518-524.

Fox, R. L., J. L. Weaver, and R. C. Lipps. 1953. Influence of certain soil profile
characteristics upon the distribution of roots of grasses. Agron. J. 45:583-589.

Freund, R. J ., and W. J. Wilson. 1993. Statistical Methods. Academic Press, Inc., San
Diego, CA.

Howard, D. D., and D. D. Tyler. 1989. Nitrogen source, rate, and application method for
no-tillage corn. Soil Sci. Soc. Am. J. 53:1573-1577.

Jackson, J. E., and Burton, G. W. 1962. Influence of sod treatment and nitrogen
placement on the utilization of urea nitrogen by coastal bermudagrass. Agron. J.
54:47-49.

King, J. W., and C. R. Skogley. 1969. Effect of nitrogen and phosphorus placement and
rates on turfgrass establishment. Agron. J. 61 :4-6.

King, J. W., and J. B. Beard. 1972. Postharvest cultural practices affecting the rooting
of Kentucky bluegrass sods grown on organic and mineral soils. Agron. J. 64:259-
262.

Lamond, R. E., and J. L. Moyer. 1983. Effects of knifed vs. broadcast fertilizer
placement on yield and nutrient uptake by tall fescue. Soil Sci. Soc. Am. J. 47: 145-
149.

Mancino, C. F., W. A. Torello, and D. J. Wehner. 1988. Denitrification losses from
Kentucky bluegrass sod. Agron. J. 80:148-153.

Mengel, D. B., D. W. Nelson, and D. M. Huber. 1982. Placement of nitrogen fertilizers
for no-till and conventional till corn. Agron. J. 74:515-518.

34

35

Miller, C. M. 1994. Turfgrass response to fertilization and cultivation using high
pressure water injection. M.S. thesis. Michigan State Univ., East Lansing.

Miller, C. M., and P. E. Rieke. 1994. Subsurface fertilization with high pressure water
injection. Proc. 64th Ann. Mich. Turf. Conf. 23:87-90.

Munsell, R. 1., and B. A. Brown. 1939. The nitrogen content of grasses as influenced by

kind, frequency of application, and amount of nitrogenous fertilizer. Agron. J.
3 1 :388-3 98.

Murphy, J. A. 1994. High pressure water injection and core cultivation of a compacted
putting green. Agron. J. 86:719-724.

Murphy, J. A., and P. E. Rieke. 1992. Evaluating additional management uses for high
pressure water injection. Agron. Abs. p.174.

Murphy, J. A., and D. E. Zaurov. 1994. Shoot and root growth response of perennial
ryegrass to fertilizer placement depth. Agron. J. 86:828-832.

Ogus, I.., and R. L. Fox. 1970. Nitrogen recovery from a soil profile by Bromus inermis.
Agron. J. 62:69-71.

Peacock, C. H., and A. E. Dudeck. 1982. A comparison of organic versus mineral
grown sod for turf establishment. In Agron. Abs. p.144.

Raczkowski, C. W., and D. E. Kissel. 1989. Fate of subsurface-banded and broadcast
nitrogen applied to tall fescue. Soil Sci. Soc. Am. J. 53:566-570.

Rieke, P. E., and M. T. McElroy. 1986. Turfgrass soil management report research
report - 1985. Proc. 56th Ann. Mich. Turf. Conf. 15:2.

Rieke, P. E., and C. M. Miller. 1992. Effect of fertilizer application with the HydroJect.
Proc. 62nd Ann. Mich. Turf. Conf. 21:12-14.

Shanna, B. R., and T. N. Chaudhary. 1984. Nitrogen uptake by wheat in relation to
water regime and depth of N placement in a loamy sand soil: Measurement and
model simulation. J. Soil Sci. 35:141-148.

Stecker, J. A., D. D. Buchholz, R. G. Hanson, N. C. Wollenhaupt, and K. A. McVay.
1993. Application placement and timing of nitrogen solution for no-till corn. Agron.
J. 85:645-650.

Watschke, T. L., and D. V. Waddington. 1975. Effect of nitrogen fertilization on the
recovery of ‘Merion’ Kentucky bluegrass from scalping and wilting. Agron. J.
67:559-563.

CHAPTER TWO

Water Injection Cultivation of a
Sand Topdressed Putting Green

ABSTRACT

Sand topdressing, an application of a thin layer of sand to the turfgrass surface, is
a popular putting green management practice. Following several years frequent sand
topdressing, many golf course putting greens have a sand layer of 5 cm, or greater,
overlying a finer textured soil. Some turfgrass managers have voiced concerns of
blasting finer-textured soil to the surface, possibly sealing surface pores, when water
injection cultivation (WIC) is exercised on these types of putting greens. A study was
initiated in August, 1994, to examine the effects of WIC and Hollow tine cultivation
(HT C) treatments on the mixing of a sand topdressing layer with the underlying native
soil. Treatments included three frequencies of WIC (weekly, biweekly, and monthly),
HTC twice per year, and a control. ‘Penncross’ creeping bentgrass (Agrostis paIustrr's
Huds.) sod was laid on a 5 cm layer of sand, overlying a loam soil, to represent a putting
green with a significant accumulation of topdressing sand. There were no differences in
soil mixing among cultivation treatments in September 1995. In September 1996 WIC
weekly plots had more sand and less clay in the underlying soil than HTC and control
plots. WIC weekly plots also had less sand in the topdressing layer. There was no
evidence of soil mixing beyond 2.5 cm above or below the topdressing sand-native soil

interface. These mixing characteristics are likely to benefit water percolation and root

36

37

penetration at the topdressing sand-native soil interface. Control plots exhibited
significantly more moisture stress symptoms than cultivated plots during periods of high
evapotranspiration. Although there were no differences in root mass densities among the
treatments, turf receiving cultivation treatments appeared to have more active roots within
the soil profile based on visual observation. The rolling action of the WIC equipment

resulted in a 6 to 10 percent increase in ball roll distance on the day of treatment.

38

Introduction

Sand topdressing is the application of a thin layer of sand to the surface of a
turfgrass area. This cultural practice has been utilized on putting greens since the early
days of turfgrass management at St. Andrews Golf Course in Scotland (Zontek, 1976).
Benefits from frequent sand topdressing of putting green turf include increased surface
uniformity and smoothness, modification of surface soil, improved turfgrass color, tighter
and finer textured turf, and dilution of the thatch layer (Beard, 1973). These benefits
have made sand topdressing a popular putting green cultural practice utilized by many
turfgrass managers. After several years of regular topdressing, a sand layer builds to a
point where it becomes the primary medium for root growth.

Golf course putting greens are subjected to high levels of traffic, which may cause
several problems. Soil compaction resulting from intense trafic negatively impacts
turfgrass health by decreasing oxygen difl‘usion, water infiltration and percolation rates.
Compaction has also been reported to decrease turfgrass shoot and root growth rates,
nitrogen use per unit area, and visual quality (Sills and Carrow, 1982). Hollow tine
cultivation (HT C) is ofien used in the spring and fall to relieve soil problems resulting
from compaction. Traditional core cultivation is normally avoided during the mid-season
because of disruption of the putting green surfaces interferes with play. These mid-
season months, however, are when traffic is at a maximum and so is the need for
cultivation. High pressure water injection cultivation (WIC) has gained popularity in
recent years as a method of cultivating putting greens while causing minimal surface
disruption, which makes it an ideal tool for mid-season cultivation. The Toro HydroJect
3000o blasts a 20 MPa jet of water 10 to 20 cm below the soil surface (Murphy and
Rieke, 1994). There is some concern whether using high pressure water injection to

cultivate putting greens with a significant sand topdressing layer blasts underlying native

39

soil to the surface of the putting green. If so, finer-textured soil blasted to the putting
green surface could possibly seal surface pores, negatively impacting soil physical
properties. Soil fines settling in surface macropores would likely decrease air-filled
porosity and increase the tortuosity of the surface soil. Oxygen diffusion and water
infiltration rates decrease with a decrease in air-filled porosity and an increase in
tortuosity (Hillel, 1982).

The objective of this study was to determine the effects of WIC and HTC on a
putting green that contains a significant sand layer overlying a native, finer-textured soil.
Cultivation treatments, which were initiated during the summer of 1994, included three

frequencies of WIC, HTC twice per year, and a control.

mm

Research regarding the mixing of soil layers as affected by cultivation has been
extremely limited. Previous research concerning putting green cultivation has almost
exclusively focused on physical properties of the bulk soil. Past sand topdressing
research has primarily regarded effects on thatch, microbial populations, and turfgrass
quality.

Conventional hollow tine cultivation is often practiced to improve infiltration
rates. Cultivation of a Kentucky bluegrass turf (Poa pratensis L.) growing on compacted
soil decreased runoff (Alderfer, 1954). Conversely, core cultivation has been attributed to
a decrease in infiltration, probably resulting from the creation of a compaction pan just
beneath the cultivation depth (Murphy et. al, 1993). Verti-Drain units with hollow tines
have reportedly loosened soil to depths of up to 20 cm to prevent compaction pan
development (Murphy and Rieke, 1989). Vertical mowing and hollow tine cultivation
treatments were both reported effective in reducing thatch (Murray and Juska, 1977).
Biweekly hollow tine cultivation of ‘Tifdwarf’ bermudagrass (Cynadon dactylon L. Pers.

40

x Cynadon transvaalensis Burtt-Davy) reduced thatch weight, and to a lesser extent,
thatch thickness (Smith, 1979). High pressure water injection cultivation increased
macropores relative to unheated soil and was as effective as hollow tine cultivation at
improving bulk density, porosity, and saturated hydraulic conductivity (Murphy and
Rieke, 1994).

Sand topdressing primarily functions to provide a firm, uniform putting surface
while diluting the thatch. Biweekly sand topdressing of a ‘Penncross’ creeping bentgrass
(Agrostis palustris Huds.) putting green provided a true, firm surface while providing
adequate thatch to cushion and lessen ball marks and reduce ball bounce (Murphy, 1983).
An autumn sand topdressing application improved spring recovery of a ‘Penncross’
creeping bentgrass putting green (Christians et al., 1985). Sand topdressing of a heavily
thatched creeping bentgrass green reduced the organic content of the thatch and
improved visual quality during summer months (F ermanian et al., 1985). In that study,
however, topdressed turf had greater incidences of diseases and annual bluegrass (Poa
annua L.) infestation. Four sand topdressings per year applied to three different
bermudagrass cultivars decreased the thatch thickness, but increased the combined
thickness of the thatch and mat layer (White and Dickens, 1984). Similarly, sand
topdressing increased mat and root weights of a zoysiagrass turf (Zoysiajaponica Steud.)
(Dunn, et al., 1995). Sand topdressing was demonstrated to have no effects on microbial
populations of ‘Penneagle’ creeping bentgrass putting greens (Robbeloth et al., 1987).

Materials and Methods

The sand topdressing study was conducted at the Hancock Turfgrass Research
Center on the Michigan State University campus. Creeping bentgrass putting green sod,
growing on a fine-loamy, mixed, mesic, Typic Hapludalf, was removed on 17 May, 1994.

Approximately five centimeters of topdressing sand (96% sand, 3% silt, and 1% clay)

41

was placed over the native soil to simulate a long term topdressing program. The putting
green was sodded on 27 May with ‘Penncross’ creeping bentgrass, provided by Hugget
Sod Farm, Marlene, MI, which was harvested from a sand soil similar to the sand used in
this study. The experimental area was mowed at 0.5 cm and maintained under typical
putting green management practices. Mowing was performed five times per week during
the majority of the growing season. Irrigation was applied daily unless the turf received
sufficient water fiom precipitation. Pesticides were applied on a curative basis.
Cultivation treatments were initiated when the sod had rooted down well, approximately
11 weeks following establsihment. Treatments included three frequencies of water
injection cultivation (WIC) (weekly, biweekly, and monthly), HT C in the spring and fall,
and a control. Water injection cultivation was accomplished with a HydroJect 3000’
provided by the Toro Company, Minneapolis, MN. The HydroJect was operated at the
closest nozzle spacing, approximately 7.5 cm by 2.5 cm. Hollow tine cultivations were
achieved with a Ryan Greensaire provided by the Ransomes America Corporation,
Lincoln, NE. Hollow tines were 1.0 cm in diameter and operated at a 7.5 cm by 5.0 cm
spacing. Cores were brushed in following cultivation and the remaining thatch was
removed.

Water injection cultivation treatments were initiated 16 Aug, 1994, and continued
until 29 Sep., 1994. The first HTC treatment was applied 13 Oct., 1994. Treatments
were applied from 15 May to 15 Oct. in 1995 and 17 May to 4 Oct. in 1996. Hollow tine
cultivation treatments were applied on the first and last treatment dates of both 1995 and
1996. A light sand topdressing (approximately 0.0032 m3 sand m‘z) was applied
approximately every three weeks throughout the study.

Turfgrass quality ratings were taken monthly throughout the growing season.
Quality ratings were based on turfgrass uniformity, density, and color. Plots were ranked
on a scale from 1 to 9 with 1 being dead turf, 6 minimum acceptable quality, and 9
uniform, dense, dark green turf. Quality ratings were taken on 7 Sep. and 10 Oct. in

42

1994, 11 May, 13 Jun., 1 Aug., and 7 Sep. in 1995, and 17 May, 24 Jun., 29 Jul., 30 Aug,
27 Sep., and 25 Oct. in 1996.

Wilt ratings were taken when noticeable drying occurred over the experimental
area on 8 Jul., 1996. The plots were dried down to exacerbate moisture stress symptoms
and two additional wilt ratings were taken on 9 Aug. and 17 Aug. in 1996. Ratings
values were based on a scale of 1 to 9 with 1 being no wilt, 6 moderate wilt, and 9 severe
wilt.

Golf ball roll measurements were taken weekly, on days of treatment in 1994 and
early 1995. Readings were taken on all plots prior to treatment, and immediately after for
only those plots receiving treatment. Golf ball roll was evaluated using a USGA
Stimpmeter (Radko, 1980). Three golf balls were rolled in two opposite directions to
obtain an average roll distance for each plot. Golf ball roll measurements were taken on
24 Aug., 31 Aug., 7 Sep., and 19 Sep. in 1994; 2 Jun., 12 Jun., and 19 Jun. in 1995; and
21 May, 28 May, 9 Jul., and 1 Aug. in 1996.

Soil samples were taken 18 Sep., 1995, at 2.5 cm intervals, to a depth of 12.5 cm
for particle size analyses. Some of these samples included the sand topdressing-native
soil interface, which increased the variability of the data. Sampling directly at the
interface was avoided in 1996 to decrease variability. Since the interface was easily
detectable, samples were collected at 0 to 2.5 cm and 2.5 to 5.0 em, both above and below
the topdressing-native soil interface. Soil samples were collected on 15 Sep. in 1996.
Particle size analyses were performed by the pipette method (Day, 1965). Soil textures
differing from control plot textures were assumed to be the result of cultivation treatment.

Undisturbed soil cores were taken in October of 1995 and 1996 to determine
saturated hydraulic conductivity, bulk density and pore size distribution. Soil cores were
extracted by pounding 7.5 cm by 7.5 cm aluminum cylinders into the soil, lifting the
cores containing turf and soil, and cutting of the thatch and verdure (Blake, 1963). Soil

cores were refiigerated at 4° C immediately upon excavation until laboratory analysis.

43

Saturated hydraulic conductivites were evaluated using the constant-head method
described by Klute (1963). Pore sized distributions were evaluated by breaking down
pore space into macropores and micropores. Macropores were determined by draining
saturated soil cores with a positive pressure of 0.4 MPa using the pressure chamber
method (V omocil, 1 963).

The soil profile in this study was constructed to simulate a golf course putting
green that has been on a light, frequent topdressing program for several years. The
putting green used in this study lacked the gradual accumulation of root mass and organic
matter that would normally occur with a light, frequent topdressing program.
Fortunately, Rutgers University had a research putting green with a significant sand
topdressing layer, accumulated over several years of light frequent applications,
overlying a finer textured soil. A two year cultivation study was conducted by Dr. James
Murphy on this putting green in 1994 and 1995 with water injection cultivation
treatments. Treatments on this study included WIC weekly, WIC triweekly, and a
control. Treatments were replicated four times. The WIC weekly treatment had been
applied 25 times and the WIC triweekly treatment had been applied 9 times prior to the
collection of soil samples. Soil samples were collected Jun. 28, 1996 from the Rutgers
study with the cooperation of Dr. Murphy and brought to Michigan State University for
particle size analysis. Soil textures in WIC plots statistically different from control plot
textures were assumed to be the result of cultivation treatment. These results were used
to help verify results obtained from the model sand topdressed putting green.

A randomized complete block design was used as the experimental model with
three treatments replications for the Michigan State Study. A randomized complete block
design with four replications was used as the experimental model for the Rutgers study.
A one factor analysis of variance was calculated for all data to indicate treatment
difi‘erences. Treatment means were determined significantly different at probabilities S

0.05. and separated using Fisher’s protected least significant difference procedure

(Freund and Wilson, 1993). Results are reported by constructing 95 % confidence

intervals for differences between treatment means.

Results and Discussion

Particle size analysis

Particle size analysis data for soil samples taken on 18 Sep., 1995 are summarized
in Table 2.1. There were no significant differences in percent sand or clay among any
cultivation treatments at any depth in 1995. The 1995 soil samples were taken after a 1.5-
year total of 7 WIC weekly treatments, 15 WIC biweekly treatments, 9 WIC monthly
treatments, and 3 HTC treatments were applied.

Particle size analysis data for soil samples taken on 15 Sep., 1996 are summarized
in Table 2.2. These samples were taken after a 2.5-year total of 48 WIC weekly
treatments, 27 WIC triweekly treatments, 15 WIC monthly treatments, and 5 HT C
treatments. There were no significant differences in percent clay or sand among any
cultivation treatmentsat 2.5 to 5.0 cm above, and below, the sand-native soil interface.

There were no significant differences in percent clay among cultivation treatments
in the O to 2.5 cm layer above the sand-native soil interface. However, there were
significant differences (P s 0.05) in percent clay at the 0 to 2.5 cm layer below the
interface and in sand content at the 0 to 2.5 cm layer both above and below the interface.
Significant differences in clay content on only one side of the sand-native soil interface
was probably the result of slight error in measurement causing a relatively large
experimental error and no significant treatment effects above the interface.

Water injection cultivation weekly samples contained 2.4 :1: 0.7 percent less clay
and 7.1 i 0.5 percent more sand than check samples at the 0 to 2.5 cm layer below the
sand-native soil interface. Water injection cultivation weekly samples contained 6.1 :1:
0.5, 5.3 :1: 0.5, and 3.5 :1: 0.5 percent more sand, respectively, than HTC, WIC monthly,

45

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47

and WIC biweekly samples at the 0 to 2.5 cm layer below the sand-native soil interface.
Water injection cultivation biweekly samples contained 3.6 :I: 0.5 and 2.6 i 0.5 percent
more sand, respectively, than check and HTC samples 0 to 2.5 cm below the sand-native
soil interface.

Check samples and HT C samples were not significantly different (P S 0.05) in
sand content at the 0 to 2.5 cm layer above the sand-native soil interface. Hollow tine
cultivation samples contained 5.1 :t: 1.0 and 2.9 i 1.0 percent more sand, respectively,
than WIC weekly and WIC biweekly samples at the 0 to 2.5 cm layer above the sand-
native soil interface. Check samples contained 4.8 i 1.0 and 2.6 :t: 1.0 percent more sand,
respectively, than WIC weekly and WIC biweekly samples at the O to 2.5 cm layer above
the sand-native soil interface. WIC monthly samples contained 4.0 :1: 1.0 percent more
sand than WIC weekly samples 0 to 2.5 cm above the sand-native soil interface.

These data suggest that significant mixing of the sand topdressing layer and
underlying native soil occurs after several treatments. Although soil textures among
cultivation were statistically different, their actual differences were small and need to be
watched over a long period of time. All detectable soil layer mixing took place within
2.5 cm of the sand topdressing-native soil interface. A larger percentage of topdressing
sand moved into the underlying soil than clay moved into the topdressing layer. These
layer mixing characteristics are considered beneficial in the soil immediately above and
below the interface. Abrupt soil texture changes impede water percolation (Hillel, 1982)
and root penetration. Casimaty et. al (1993) found that transplanting washed sod
increased rooting and infiltration compared to transplanting sod containing soil different
in texture fi'om the soil on site. Layer mixing by cultivation should alleviate detriments
associated with soil layering. There was no evidence of clay accumulating at the soil
surface with any cultivation treatment. Cultivation did not appear to play a role in sealing
surface pores of the sand topdressing layer with finer textured underlying soil in this
study. Turfgrass managers may find WIC beneficial when used in conjunction with the

48

initiation of a light, frequent sand topdressing program. Water injection cultivation
treatments could cause mixing at the interface of a sand topdressed green by
incorporating topdressing sand into the underlying soil and vice versa as long as soil
layers are compatible.

Quality ratings

Quality rating data for all rating dates are summarized in Table 2.3. Water
injection cultivation treatments decreased quality at the beginning of the study, probably
by damaging the root system of the recently laid sod. All WIC treatments ranked
significantly lower than the HT C and check treatments on 7 Sep., 1994, approximately
three weeks after treatments were initiated (as 3 mos. after sod was laid).

Turf quality ratings were lowest in 1995 due to an unusually stressful summer.
Hollow tine cultivated plots had significantly low quality on 11 May (as 5 mos. afier
treatment) and 13 Jun. (29 days afier first 1995 treatment) resulting from aerification
holes reducing turf uniformity. The weekly and biweekly WIC treatments had
significantly low quality on 1 Aug., 1995. Frequent WIC probably damaged an already
weak root system that was under stress because of weather extremes. Quality ratings
were still significantly low for the WIC weekly treatment on 7 September.

Quality ratings were initially low in 1996, resulting from a harsh summer the
previous year and a cold spring in 1996, but increased with improving weather
conditions. Frequent WIC treatments did not significantly (P S 0.05) lower turf quality
when weather conditions were more optimal 1996. The HTC treatment had significantly
low quality on 24 Jun. (38 days afier treatment) and 25 Oct. (16 days after treatment),
resulting fi'om aerification holes reducing turf uniformity. Check plots had significantly
low quality on 30 Aug. and 27 Sep. resulting from moisture stress symptoms when the

experimental area was dried down.

49

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50

Wilt ratings

Wilt rating data taken in 1995 are summarized in Table 2.4. The check treatment
had significantly increased moisture stress symptoms (P S 0.05) than all cultivation
treatments on the 8 Jul. and 17 Aug. rating dates. Check plots had significantly increased
moisture stress symptoms than the WIC weekly, WIC monthly, and HTC treatments on '
the 9 Aug. rating date. There were no significant differences in moisture stress symptoms
among turfs that received some type of cultivation treatment on all three dates that plots
were rated.

Soil samples were excavated from 2.5 to 7.5 cm and 7.5 to 15 cm in September,
1995 to evaluate a possible correlation between root mass density and moisture stress
symptoms. During sampling, a greater abundance of white roots, particularly in the
aerification channels, were apparent at lower soil depths in plots receiving frequent WIC
treatments and HTC treatment. However, there were no significant differences in root
mass density at either sampling depth (P S 0.05) among the treatments upon analysis
(Table 2.5). There was probably a greater mass of active roots at lower soil depths, but
root mass analysis could not distinguish between living and dead roots. Turf under
moisture stress probably had increased root turnover and therefore a combined root mass
density of living and dead roots not significantly different from non moisture stressed
turf. Cultivation treatments probably increased porosity and oxygen levels at greater soil
depths, encouraging root initiation (Hillel, 1982; Taiz and Zieger, 1991). These deep root
systems would be capable of extracting moisture at greater depths than more shallow
active roots of non cultivated turf.
Stimpmeter evaluations

Stimpmeter data are surmnarized for 1994, 1995, and 1996, respectively, in
Tables 2.6, 2.7, and 2.8. There were no differences in ball roll distance among the
treatments prior to application on any dates that plots were evaluated. Ball roll distance

was significantly low for the HTC treatment on Aug. 31, 1994. Treatment applications

51

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56

resulted in significantly increased ball roll distances for WIC treated plots on 12 Jun. in
1995, and 28 May and 1 Aug. in 1996. The HydroJect 3000’ has two rollers surrounding
the injection nozzles that function similar to traditional putting green rollers. This rolling
action increased ball roll distances on plots receiving WIC treatment, probably by
decreasing surface irregularities (Beard, 1997). Ball roll increases following WIC
treatment averaged 6 percent in 1994, 10 percent in 1995, and 8 percent in 1996. These
increases in ball roll distance are similar to those observed in studies evaluating
traditional greens rollers (Beard, 1997). Similar ball roll data was reported by Miller
(1994) where WIC treatment resulted in an immediately increase in ball roll distance that
averaged 22 percent.

Soil physical properties

Saturated hydraulic conductivity, porosity, and bulk density data are summarized
in Tables 2.9 and 2.10. There were no significant differences among cultivation
treatments for any soil property in 1995 and 1996. Saturated hydraulic conductivity and
porosity data were somewhat lower in 1996 than in 1995. A decrease in saturated
hydraulic conductivity could have been caused by an increase in root mass and organic
matter in macropore space. Lodge and Baker (1993) reported significant decreases in
infiltration rates of sand based root-zones probably due to the sealing off of the surface
pores with organic material. A decline in porosity could have resulted from settling of
the sand topdressing layer, compaction fi'om mowers and foot traffic, or possibly a
combination of both.

These results were somewhat surprising, and not typical for cultivation
treatments. Hollow tine cultivation and WIC treatments typically increase hydraulic
conductivity and porosity, and lower bulk density. Murphy and Rieke (1994) reported
that WIC was equal or superior to HTC in reducing soil bulk density, and increasing
porosity and saturated hydraulic conductivity. In another study, Murphy et. a1 (1993)

57

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59

reported a 3 percent decrease in bulk density with and 62 % increase in saturated
hydraulic conductivity with HTC.

Variability among treatments was high within the 5 soil cores extracted per plot.
This may have been the result of earthworm activity. Several earthworms surfaced from
check treatment soil cores following saturation. Earthworm burrowing may have
increased porosity and saturated hydraulic conductivity in check soil cores to a level not
significantly different fi-om cultivation treatment soil cores.

Particle size analysis (Rutgers University samples)

Particle size analysis data fi-om the Rutgers University cultivation study are
summarized in Table 2.11. Check samples had 2.7 :l: 0.2 and 0.6 :t 0.2 percent more sand
in the topdressing layer, respectively, than WIC weekly and WIC triweekly samples.
Water injection cultivation triweekly samples had 2.1 :t 0.2 percent more sand in the
topdressing layer than WIC weekly samples. Water injection cultivation weekly samples
had 1.2 :t 0.4 percent more clay in the topdressing layer than check samples. Check
samples had 4.1 :t 1.6 and 2.8 i 1.6 percent less sand, respectively, than WIC triweekly
and WIC weekly samples in the underlying native soil. There were no significant
differences among treatments in clay content in the underlying soil. This data correlates
fairly well with the data obtained from the constructed model sand topdressed putting
green.

Summary

Mixing of a sand topdressing layer and a finer-textured underlying soil became
significant after several WIC treatments. Water injection cultivation treatments had a
greater effect on the mixing of soil layers than the HTC treatment. Soil layer mixing was
not evident at distances greater than 2.5 cm from the sand topdressing-native soil
interface. These data were obtained from a model putting green constructed to represent
several years of sand topdressing and correlates well to data obtained from a Rutgers

University putting green study that had a significant sand layer fiom years of light,

60

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61

frequent topdressing. Turfgrass managers initiating a topdressing program may benefit
by supplementing it with WIC treatments. Light, frequent sand topdressing in tandem
with regular WIC treatments may provide a smooth uniform playing surface while
preventing the development of a zone with an abrupt change in soil texture that would
occur without cultivaition.

Frequent WIC treatments during periods of summer stress, and on young sod,
reduced turf quality. Stressed turf seemed to respond negatively to weekly and biweekly
WIC, possibly from damage to an already weakened root system. Turfgrass managers
should consider weather conditions and perhaps reduce WIC intensity when turfgrass
vigor is sub-optimal. For mature greens, one should evaluate carefully the effect of high
frequency of WIC to ensure there is not excessive injury to roots.

Plots receiving no form of cultivation had increased moisture stress symptoms
during periods of high evapotranspiration. This likely resulted from increased amounts of
active roots deeper in the soil profile for turf that received cultivation treatments. Greater
root mass densities could not be quantified by laboratory analysis. Root mass density
analysis did not distinguish between living and dead roots.

HydroJect treatments results in a 6 to 10 % increase in ball roll distance
immediately following treatment application. These increases are caused by the
smoothing action of the two rollers located on either side of the injection nozzles on the
HydroJect. Similar increases in ball roll distances have been reported in previous

HydroJect research as well as research evaluating traditional greens rollers.

BIBLIOGRAPHY

Alderfer, R. B. 1954. Effects of soil compaction on bluegrass turf. Penn. State College
Turfgrass Conf. 23:31-32.

Beard, J. B. 1997. Greens rollers help golf balls roll farther. Golf Course Manage.
65(1):49—53.

Beard, J. B. 1973. Turfgrass science and culture. Prentice-Hall, Inc., Englewood Cliffs,
NJ. p 494-495.

Blake, GR. 1965. Bulk density. p. 374-376. In D.D. Evans (ed.) Methods of Soil
Analysis. Part 1. Agron. Monogr. 9. ASA and SSSA, Madison, WI.

Casimaty, B. G., J. Neylan, and J. B. Beard. 1993. Effects of soil removal by post
harvest hydraulic washing on sod transplant rooting of a Kentucky bluegrass-
perennial ryegrass polystand and a creeping bentgrass monostand. Proc. Seventh Int.
Turfgrass Res. Conf. 7:850-856.

Christians, N. E., K. L. Diesburg, and J. L. Nus. 1985. Effects of nitrogen fertilizer and
fall topdressing on the spring recovery of Agrostis palustris Huds. (Penncross
creeping bentgrass) greens. Proc. of the Fifth International Turfgrass Research
Conference. 5:459-468.

Day, P. R. 1965. Pepette method of particle-size analysis. p. 552-561. In D.D. Evans
(ed.) Methods of Soil Analysis. Part 1. Agron. Monogr. 9. ASA and SSSA,
Madison, WI.

Dunn, J. H., D. D. Minner, B. G. Fresenburg, S. S. Bughrara, and C. H. Hohnstrater.
1995. Influence of core aerification, topdressing, and nitrogen on mat, roots, and
quality of ‘Meyer’ zoysiagrass. Agron. J. 87:891-894.

Fermanian, T. W., J. E. Haley, and R. E. Burns. 1985. The effects of sand topdressing
on a heavily thatched creeping bentgrass turf. Proc. of the F ifih Int. Turfgrass Res.
Conf. 5:439-448.

Freund, T.W., and W.J. Wilson. 1993. Statistical Methods. Academic Press, Inc., San
Diego, CA.

62

63

Murphy, J. A. 1986. Hollow and solid tine cultivation effects on soil structure and
turfgrass root growth. MS. Thesis. Michigan State Univ., East Lansing.

Hillel, D. 1982. Introduction to soil physics. Academic Press, Inc., San Diego, CA. p.
135-252.

Murphy, J .A. and RE. Rieke. 1994. High pressure water injection and core cultivation
of a compacted putting green. Agron. J. 86:719-724.

Klute, A. 1965. Laboratory measurement of hydraulic conductivity of saturated soil. p.
210-220. In D.D. Evans (ed.) Methods of Soil Analysis. Part 1. Agron. Monogr. 9.
ASA and SSSA, Madison, WI.

Lodge, T. A., and S. W. Baker. 1993. Porosity, moisture release characteristics and
infiltration rates of three golf green rootzones. J. Sports Turf Res. Inst. 69:49-58.

Miller, C. M. 1994. Turfgrass response to fertilization and cultivation using high
pressure water injection. M.S. thesis. Michigan State Univ., East Lansing.

Murphy, J. A., and P. E. Rieke. 1994. High pressure water injection and core cultivation
of a compacted putting green. Agron. J. 86:719-724.

Murphy, J. A., P. E. Rieke, and A. E. Erickson. 1993. Core cultivation of a putting green
with hollow and solid tines. Agron. J. 85: 1-9.

Murphy, J. W. 1983. Effect of topdressing medium and frequency on thatch
accumulation by Penncross bentgrass in golf greens. J. Sports Turf Res. Inst. 59:46-
50.

Murray, J. J. and F. V. Juska. 1977. effects of management practices on thatch
accumulation, turf quality and leaf spot damage in common Kentucky bluegrass.

Agron. J. 69:365-369.

Radko, A. M. 1980. The USGA Stimpmeter for measuring the speed of putting greens.
Proc. Third Int. Turfgrass Res. Conf. 3:473-476.

Robbeloth, E. K., C. S. Throssell, and R. F. Turco. 1987. Microbial ecology of
topdressing and topdressing created layers on bentgrass golf greens. p. 138. In
Agronomy abstracts. ASA, Madison, WI.

Sills, M. J ., and R. N. Carrow. 1982. Soil compaction effects on nitrogen use in tall
fescue. J. Amer. Soc. Hort. Sci. 107:934-937.

Smith, G. S. 1979. Nitrogen and aerification influence on putting green thatch and soil.
Agron. J. 71 :680-684.

Taiz, L., and E. Zieger. 1993. Plant Physiology. Benjamin Cummings Publishing
Company, Inc., Redwood City, CA. p. 365.

White, R. H. and R. Dickens. 1984. Thatch accumulation in bermudagrass as influenced
by cultural practices. Agron. J. 76:19-22.

Vomocil, J.A. 1965. Pore-size distribution. p. 300-314. In D.D. Evans (ed.) Methods of
Soil Analysis. Part 1. Agron. Monogr. 9. ASA and SSSA, Madison, WI.

Zontek, S. J. 1979. Is sand topdressing right for you? Golf Course Manage. (6):15-21.

CHAPTER THREE

Cultivation Effects on Poa annua Encroachment
into a Creeping Bentgrass Putting Green.

ABSTRACT

Core cultivation of putting greens is often practiced during the spring and/or fall,
coinciding with optimal conditions for PM annua L. reptans germination. Soil
disturbance from hollow tine cultivation (HT C) provides space and light, enhancing the
potential for germination of P00 annua. High pressure water injection cultivation (WIC)
is a relatively new technique developed to cultivate turf areas while causing minimal
surface disruption. This study was conducted to compare the effects of different
fi'equencies of HT C and WIC, and combinations of HTC and WIC on Poa annua
encroachment into a creeping bentgrass (Agrostis palustris Huds.) putting green growing
on a loamy sand soil (modified fine-loamy, mixed, mesic, Typic Hapludalf). The
experiment consisted of eight treatments: WIC weekly; WIC biweekly; WIC monthly;
HTC spring and fall; HTC spring, summer, and fall; HTC spring and fall and WIC
biweekly; and HTC spring and fall at a narrow tine spacing in combination with WIC
biweekly; and a control. A HydroJect 3000’ was used to apply WIC treatments. Poa
annua populations were counted in the spring and fall of 1994, 1995, and 1996.
Turfgrass quality, ball roll distance, soil physical properties, and earthworm populations

were also evaluated periodically. Poa annua populations were not affected by cultivation

65

66

treatments throughout the study. Populations decreased slightly with all treatments
during 1994 and 1995. A compaction treatment was initiated in 1996, which resulted in
slight increases in populations for all cultivation treatments. Surface disruptions in plots
receiving HTC treatments significantly decreased turfgrass quality for up to 21 days
following treatment. Ball roll distances on plots receiving WIC treatment increased 6 to
10 % immediately following treatment because of the rolling action the HydroJect.
Earthworm castings on the turfgrass surface were significantly decreased with weekly
WIC application. Spring and fall HTC treatments had significantly greater earthworm

biomass than the control treatment in the surface 30 cm of the soil.

67

Introduction

Poa annua L. reptans is a fine textured, cool-season turfgrass of high shoot
density that is well adapted to mowing heights under 1.25 cm. Although Poa annua can
provide a quality turf if properly maintained, it is never intentionally included in seed
mixtures and is generally considered a weed. Encroaching Poa annua, easily identified
by its lighter yellow-green color and prolific seed head formation, decreases the visual
and functional quality a creeping bentgrass (Agrostis palustris Huds.) putting green. Poa
annua is extremely prone to disease in hot, humid weather, which becomes apparent on
infested putting greens and fairways during mid-summer months (Beard, 1973).

Turfgrass researchers have been investigating controls for Poa annua since 1917
when it was noted that dense growing creeping bentgrasses were less susceptible to weed
infestation (Robinson, 1952). The demand by golfers for luxurious turf and all-season
good play resulted in increases in irrigation and closer mowing heights in the early
1960’s (Schery, 1968). These changing cultural practices gave Poa annua an ecological
boost to compete with fine fescue (Festuca spp.) and creeping bentgrass. Arsenate
containing herbicides were somewhat effective at reducing Poa annua populations (Kerr,
1968; Twombly, 1952), but these chemicals were taken off the market in the early
1970’s. Since then, turfgrass managers have been battling Poa annua infestations with
limited success. Putting green re-construction that includes soil sterilization has been the
most effective Poa annua control in recent years, but it is extremely costly and Poa
annua plants typically reappear within 3 to 5 years.

Putting green core cultivation, a cultural practice to relieve soil compaction, is
often utilized during cool periods of the growing season to limit both turfgrass stress and
disruption of play. These cooler periods are when germination of PM annua is most

favorable (Cockerham and Whitworth, 1967). It has been recognized that soil

68

disturbance from core cultivation may enhance Poa annua germination and increase
infestation severity (Schmidt and Shoulders, 1972; Bengeyfield, 1969; Youngner, 1968;
Beard, 1973). Water injection cultivation (WIC) was introduced in 1990 as an effective
means of cultivation while causing minimal surface disruptions (Murphy and Rieke,
1994). The use of WIC on creeping bentgrass putting greens may reduce Poa annua
infestations compared to traditional core cultivators during periods of favorable Poa
annua germination.

The objective of this research was to determine the efl‘ects of cultivation method
and frequency on Poa annua infestation of a creeping bentgrass putting green.
Treatments included three frequencies of WIC, two frequencies of hollow tine cultivation

(HTC), two combination treatments, and a control.

Literature Review

Poa annua research dates back to 1917, when Hartman and Damon found that
dense growing Rhode Island creeping bentgrass was resistant to invasion by weeds
(Robinson, 1952). Since then, a wealth of studies have followed investigating factors that
encourage, or discourage, Poa annua infestations.

Evans (1932) advised that maintaining sheep on a golf course may increase Poa
annua incidence through colonization of sheep scalds. Cockerham and Whitworth (I 967)
discovered that 16 °C was the optimal germination temperature for Poa annua seeds at
several different seed aging intervals. Koch (1968) discovered that Poa annua
germinated over a wide range of temperatures and there were hardly any limiting
temperatures (except frost) for germination under natural conditions.

Roberts (1986) demonstrated that Poa annua is often a major contributor to seed
banks of arable, as well as grassland soil. In that study, Poa annua germination from a
weed seed bank was consistently high throughout each of four years and highest

69

following soil disturbance. In a similar study, Roberts and Ricketts (1979) found that
Poa annua was one of the most frequent weed seed species found in a wide range of
agricultural soils.

Two studies conducted in the mid 1980’s investigated the effects of turfgrass
cultivation on pre-emergent herbicide efficacy and subsequent annual grass infestation.
Branham and Rieke (1986) found that neither cultivation method nor cultivation timing
had an effect on pre-emergent herbicide efficacy, and subseqent crabgrass invasion, on a
Poa annua var. reptans fairway. Similarly, Johnson (1987) found that core cultivation
timing had no effect on crabgrass invasion of a bermudagrass (Cynodon dactylon L.
Pets.) turf.

Schmidt and Shoulders (1972) discovered that turf receiving early summer
cultivations and twice-cultivated turf contained significantly higher amounts of Poa
annua than control plots. It was concluded that cultivation in late May to early June
provided an excellent seedbed, which coincided with the natural seeding of P00 annua.
Delaying cultivations until Poa annua seed production ceased reduced infestation.

Materials and Methods

This study was initiated in June, 1994 at the Hancock Turfgrass Research Center
at Michigan State University on a 4-year old ‘Penncross’ creeping bentgrass green
growing on a modified loamy sand soil (modified fine-loamy, mixed, mesic, Typic
Hapludalf). The experimental area was mowed at 0.5 cm and maintained under typical
putting green management practices. Plots were 4.6 m in length and 0.8 m wide. The
experiment consisted of the following eight treatments: Water injection cultivation
(WIC) weekly; WIC biweekly; WIC monthly; HTC spring and fall (HT CSF); HTC
spring summer and fall (HT CSSF); HTC spring and fall and WIC biweekly (HT CSFW);
and HTC spring and fall at a narrow tine spacing and WIC biweekly (HT CSF‘W); and a

70

control. Water injection cultivation was accomplished with a HydroJect 30000 provided
by the Toro Company, Minneapolis, MN. The HydroJect was operated at the closest
nozzle spacing, approximately 7.5 cm by 2.5 cm. Hollow tine cultivations were achieved
with a Jacobsen Aero-King" provided by Jacobsen Company, Racine, WI. Hollow tines
were 1.0 cm in diameter and operated at a 7.5 cm by 5.0 cm for treatments with normal
spacings and 5.0 cm by 2.5 cm for treatments narrow spacings. Cores were brushed in
following cultivation and the remaining thatch was removed.

Water injection cultivation treatments were initiated 7 Jun., 1994, and continued
until 27 Sep., 1994. Spring and fall HTC treatments were applied 9 Jun. and 13 Oct. in
1994. The summer HT C treatment was applied on 30 Aug. on appropriate plots.
Treatments were applied from 22 May to 3 Oct. in 1995 and 23 May to 10 Oct. in 1996.
Hollow tine cultivation treatments were applied on the first and last treatment dates of
1995 and 1996. Summer HTC teatrnents were applied on 28 Aug., 1995 and 7 Aug.,
1996 on appropriate plots.

Poa annua counts were made using a cormting grid to calculate population
percentages for each plot. Plant species were identified at each of 162 grid crosshairs per
count and two counts were made per plot. Counts were made in Jun. and Oct. in 1994,
and May and Oct. in both 1995 and 1996. Decreases in Poa annua populations during
1994 and 1995 prompted compaction treatments with a vibration roller in 1996 to
encourage Poa annua encroachment. Compaction treatments were made three times per
week from Jun. through Sep. with a Ryan Rollaire" (Ransomes America Corporation,
Lincoln, NE) applying approximately 50 kPa static pressure.

Turfgrass quality ratings were taken monthly throughout the growing seasons.
Quality ratings were based on turfgrass uniformity, density, and color. Plots were ranked
onascale flour 1 to9with 1 beingdeadturf,6minimumacceptable quality, and9
uniform, dense, dark green turf. Quality ratings were taken on 11 Jul., 20 Jul., 7 Sep. and

71

11 Oct. in 1994; 11 May, 14 Jun., 1 Aug., and 7 Sep. in 1995; and 23 May, 20 Jun., 25
Jul., 22 Aug., 25 Sep., and 23 Oct. in 1996.

Golf ball roll measurements were taken periodically, on days of treatment.
Readings were taken on all plots prior to treatment, and immediately after for only those
plots receiving treatment. Golf ball roll was evaluated using a USGA Stimpmeter
(Radko, 1980). Three golf balls were rolled in two opposite directions to obtain an
average roll distance for each plot. Golf ball roll measurements were taken on 11 Jul., 30
Aug., 8 Sep., and 20 Sep. in 1994; 25 May, 1 Jun., 8 Jun., and 15 Jun., and 22 Jun. in
1995; and 30 May, 14 Jun., and 21 Aug. in 1996.

Undisturbed soil cores were taken in October of 1995 and 1996 to determine
saturated hydraulic conductivity, bulk density and pore size distribution. Soil cores were
extracted by pounding 7.5 cm by 7.5 cm aluminum cylinders into the soil, lifting the
cores containing turf and soil, and cutting off the thatch and verdure (Blake, 1965). Soil
cores were refiigerated at 4° C immediately upon excavation until laboratory analysis.
Saturated hydraulic conductivites were evaluated using the constant-head method
described by Klute (1965). Pore size distributions were evaluated by breaking down pore
space into macropores and micropores. Macropores were determined by draining
saturated soil cores with a positive pressure of 0.4 MPa using the pressure chamber
method (V omocil, 1965).

Earthworm castings were counted on a few dates when a significant amount of
castings were noticeable on the experimental area. Casting counts were made on 1 Oct.,
1994, 6 Sep., 1995, and 17 Sep., 1996. Differences in castings numbers among the
treatments prompted earthworm biomass evaluations to find whether casting numbers
correlated with actual earthworm populations. Due to time constraints only the WIC
weekly, HTCSF, and control plots were sampled. Two soil samples with volumes of 25
cm by 25 cm in area by 30 cm deep were excavated per plot. The samples were sifted for

adult worms and then washed and screened for cocoons.

72

A complete randomized design was used as the experimental model with four
treatments replications. A one-way analysis of variance was calculated for all data to
indicate treatment differences. Treatment means were determined significantly different
at probabilities S 0.05 and separated using Fisher’s protected least significant difference
procedure (F reund and Wilson, 1993).

Results and Discussion

Poa annua counts

Poa annua encroachment data are summarized in Table 3.1. There were no
significant differences in percentage of P00 annua (P S 0.05) among any treatments at the
beginning of the study. Nor were were there any significant differences in percentage
Poa annua or total increase in Poa annua on any dates that counts were made. Turf plots
averaged 1.8 % on Jun, 1994 and increased to 2.6 % and 5.2 %, respectively, on the Oct.,
1994 and May, 1995 counting dates. Total increases in Poa annua percentages fell to 2.2
% on the Oct, 1995 counting date and 0.7 % on the May, 1996 counting date. These
results suggest that when turf is healthy and growing well at the time of cultivation, Poa
annua may not infest.

The experimental area received moderate, to little, traffic in 1994 and 1995. This
may explain why Poa annua plants were not significantly competitive in encroaching
into the creeping bentgrass. A vibrating compaction treatment (51 kPa static pressure)
was applied to the experimental area three times per week and irrigation rates were
increased in 1996. The Oct., 1996 counts revealed a 2.5 % increase in Poa annua since
the May, 1996 counting date.

Quality ratings

Quality rating data taken in 1994 are summarized in Table 3.2. The WIC weekly

and HTCSF*W treatments ranked significantly low in quality on the 11 Jul. rating date.

73

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75

The HTCSF*W plots ranked significantly lower in quality than all other treatments. Core
cultivation holes were still apparent on HTCSF‘W plots 32 days afier treatment. Hence,
there was a decreased rate of turf recovery from hollow tine cultivation with closer tine
spacing. The WIC weekly treatment ranked significantly lower in quality than HTCSF
and HTCSSF treatments. Weekly WIC may have damaged some turfgrass roots,
stressing the turf and lowering quality. Plots receiving HTCSSF treatments ranked
significantly lower in quality than all other treatments on the 7 Sep. rating date. The
summer hollow tine cultivation treatment was applied eight days prior to rating. Core
cultivation holes were still obvious, lowering turf uniformity and overall quality.

The 1995 quality rating data are summarized in Table 3.3. There were significant
differences among cultivation treatments on all four rating dates. The HTCSF“ W
treatment ranked significantly lower than all other treatments on the 11 May rating date,
due to slow turf recovery fiom the narrow tine spacing. Turf quality was significantly
low for the HTCSF‘W plots, even a little more than six months after treatment. All plots
receiving hollow tine cultivation ranked significantly lower in quality than the other
treatments on the 14 Jun. rating date. Core cultivation holes were still apparent 23 days
after treatment. The WIC weekly treatment ranked significantly lower than other
treatments on the 1 Aug. rating date. This was during a period of hot, humid weather
conditions and the turf was under substantial stress. Frequent WIC may have damaged
root systems of turf already weakened by high soil temperatures. Turf is slow to recover
from any injury during periods of high evapotranspiration. Effective cultivation practices
will cause some injury to turfgrass roots while modifying the soil. The HT CSSF
treatment ranked significantly lower than all other treatments on the 7 Sep. rating date
because of hollow tine cultivation treatment applied 10 days earlier. Cultivation holes
were very obvious, lowering turfgrass uniformity and overall quality.

Quality rating data for 1996 are summarized in Table 3.4. There were significant

differences in turfgrass quality among cultivation on five of six dates that ratings were

76

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78

taken. Plots receiving HTCSF‘W had significantly lower quality than all other
treatments on the 23 May rating date. This was the result of slow recovering turf
associated with narrow tine spacing. Although the 11 May rating was taken six months
after the last hollow tine cultivation treatment, HTCSF‘W plots were still exhibiting
detrimental affects from the treatment. The 5.0 by 2.5 cm tine spacing had decreased turf
density, along with the previously mentioned decreased uniformity. The HTCSF’W
treatment ranked significantly lower than the WIC weekly, WIC biweekly, HT CSFW,
and check treatments on the 20 Jun. rating date (28 days afier hollow tine cultivation
treatments). The HTCSSF treatment ranked significantly lower than all other treatments,
except the HTCSF*W treatment, on the 22 Aug. These differences occurred because of
visible core cultivation holes left from HT CSSF treatments 15 days earlier. Plots
receiving HTCSF‘W treatment still ranked significantly lower in quality than several
treatments on the 25 Sep. rating date, 49 days afier treatment. All treatments with a
hollow tine cultivation ranked significantly lower than other treatments on the 23 Oct.
rating date, again because of visible core cultivation holes 13 days after treatment.
Stimpmeter evaluations

Stimpmeter data are summarized for 1994, 1995, and 1996 in Tables 3.5, 3.6, and
3.7, respectively. Prior to treatment application, there were significant differences (P S
0.05) in ball roll distance among cultivation treatments on nine of twelve days ball roll
was evaluated.

There were no significant differences in ball roll distances among the treatments,
prior to application, on the first two evaluation dates in 1994. The HTCSSF plots had
significantly low ball roll distances on 8 Sep. because of surface disruption caused by the
summer hollow tine cultivatlons applied 9 days earlier. These plots still had significantly
lower ball roll distances than several other treatments on the 20 Sep. evaluation date, 21
days afier hollow tine cultivations. Plots receiving water injection cultivation had

significantly higher ball roll distances than other treatments, immediately following

79

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82

application, on all evaluation dates in 1994. On average, water injection cultivation
increased ball roll distance 10 % following treatment. The HydroJect 3000‘ has two
rollers surrounding the injection nozzles that function similar to traditional putting green
rollers. This rolling action increased ball roll distances on plots receiving WIC treatment,
probably by decreasing surface irregularities (Beard, 1997). Similar ball roll data was ‘
reported by Miller (1994) where WIC treatment resulted in an immediately increase in
ball roll distance that averaged 22 percent.

There were significant differences in ball roll distances among the treatments,
prior to treatment application, on all five evaluation dates in 1995. Plots that received
hollow tine cultivations had significantly low ball roll distances on 25 May because of
surface disruption caused by treatments 3 days earlier. Plots receiving hollow tine
cultivation treatment and no water injection cultivation treatment had significantly lower
ball roll distances than the other treatments on 1 Jun. These plots probably had lower ball
roll distances because the HydroJect rollers smoothed the surface disruptions caused by
hollow tine cultivation in plots with combination cultivation treatments. The HTCSF‘W
treatment had significantly higher ball roll distances than several other treatments on 8
Jun., 15 Jun., and 22 Jun. Several hollow tine cultivation treatments with narrow
spacings caused the turf to thin, based on visual observations, which supported longer
ball roll distances. Plots receiving water injection cultivation had significantly high ball
roll distances, immediately following application, on all dates except 15 Jun. in 1995. On
average, water injection cultivation increased ball roll distance 7 % following treatment.

On two of three evaluation dates in 1996, there were significant differences in ball
roll distances among treatments prior to treatment. The HTCSF‘W treatment had
significantly high ball roll distances on 30 May (7 days after hollow tine cultivation) and
21 Aug. Once again, increased ball roll distances were probably the result of thinning
turf caused by hollow tine cultivation with narrow tine spacing. The HTCSSF treatment

had significantly lower ball roll distances than all other treatments on 21 Aug. Decreased

83

ball roll distances for the HTCSSF treatment was the result of surface disruptions caused
by summer hollow tine cultivation 14 days earlier. Plots receiving water injection
cultivation had significantly higher ball roll distances than all other treatments,
immediately following application, on 30 May and 21 Aug. in 1995. On average, water
injection cultivation increased ball roll distance 6 % following treatment.

Soil physical properties

Saturated hydraulic conductivity, porosity, and bulk density data are summarized
in Tables 3.8 and 3 .9. There were no significant differences among cultivation treatments
for any soil property in 1995 and 1996. These results were somewhat surprising, and not
typical for cultivation treatments. Hollow tine cultivation and WIC typically increase
hydraulic conductivity and porosity, and lower bulk density. Murphy and Rieke (1994)
reported that WIC was equal or superior to HTC in reducing soil bulk density, and
increasing porosity and saturated hydraulic conductivity. In another study, Murphy et a1.
(1993) reported a 3 % decrease in bulk density and 62 % increase in saturated hydraulic
conductivity with HTC. Earthworm channels and occasional pieces of gravel were
observed in several samples and probably significantly increased the variability to a level
where differences among treatment means were undetectable.

Saturated hydraulic conductivity decreased substantially in 1996 (~ 600 %). This
was probably the result of compression of macropore space by the rolling treatment in
1996. The soil was not compacted from the rolling treatment, as bulk density did not
increase in 1996. However, macropore space decreased significantly in 1996 (as 80 %).
There was probably an increase in tortuosity as the macropore space decreased, resulting
in the decrease in saturated hydraulic conductivity.

Earthworm populations

Earthworm casting and biomass data are summarized in Table 3.10. There were

significant differences in cast numbers among treatments on all three dates casts were

counted. All treatments having a water injection cultivation component had significantly

 

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fewer earthworm casts than the check and hollow tine cultivation only treatments, with
the exception of the HTCSF‘W treatment on 1 Oct., 1994. The WIC weekly treatment
had significantly fewer castings than the HTCSFW, HTCSF, and HT CSF'W treatments
on 6 Sep., 1995. The WIC weekly treatment had significantly fewer castings than all
treatments with an HT C component on 17 Sep., 1996. Also on this date, WIC biweekly
and WIC monthly treatments had significantly less castings than treatments with only an
HTC component.

There was significantly more earthworm biomass in HT CSF plots than WIC
weekly or check plots (Table 3.10). Although there was 200 % less biomass in the WIC
weekly treatment than check treatment, variability was substantially high, reducing
statistical significance. These data suggest that earthworm casting numbers correlate
reasonably well with actual earthworm populations. Water injection cultivation
decreased earthworm populations in this study compared to treatments with a hollow tine
cultivation component. This may have been achieved by physical harm to the organisms
with the high pressure water streams, changes in the soil environment not conducive to
earthworm habitat, or a combination of both.

Summary

Cultivation method and frequency did not affect the P00 annua populations in this
study. A lack of traffic on the experimental area probably favored creeping bentgrass
growth during 1994 and 1995, resulting in no increase in Poa annua populations.

Turfgrass quality was reduced following hollow tine cultivations and turf
receiving cultivations with a narrow tine spacing was slower to recover. A hollow tine
spacing of 5.0 cm by 2.0 cm had a thinning effect on the turf after 3 treatment
applications. Weekly WIC reduced turf quality during periods of environmental stress.
Turfgrass managers should be aware of stressful conditions when using WIC and avoid
high frequency use when turfgrass vigor is sub-optimal.

Surface disruption from hollow tine cultivations reduced ball roll distances for up
to 21 days following treatment. Narrow tine spacing reduced turf density, based on visual
observations, after 3 applications, which probably increased ball roll distances. Water
injection cultivations resulted in a 6 to 10 % increase in ball roll distance immediately
following treatment application. These increases were caused by the smoothing action of
two rollers located on either side of the injection nozzles on the HydroJect. Similar
increases in ball roll distances have been reported in previous HydroJect research as well

as research evaluating traditional greens rollers.

Hollow tine cultivation increased and WIC decreased earthworm casting activity
when compared to check plots. Soil excavation and analysis revealed that earthworm
populations were significantly higher where hollow tine cultivation treatments had been
applied. Turfgrass managers may benefit from regular WIC by eliminating the need for
pesticide control of earthworm activity on putting greens, especially during a period of

increasing environmental awareness.

BIBLIOGRAPHY

Beard, J. B. 1973. Turfgrass: science and culture. Prentice-Hall, Inc., Englewood Cliffs,
NJ. p. 67-70.

Bengeyfield, W. H. 1969. Cultural systems on golf courses. Proc. First Int. Turfgrass
Res. Conf. 1:506-508.

Blake, GR. 1965. Bulk density. p. 374376. In D.D. Evans (ed.) Methods of Soil
Analysis. Part 1. Agron. Monogr. 9. ASA and SSSA, Madison, WI.

Branham, BE, and PE. Rieke. 1986. Effects of turf cultivation practices on the efficacy
of preemergence grass herbicides. Agron. J. 78: 1089-1091.

Cockerham, S.T., and J .W. Whitworth. 1967. Germination and control of annual
bluegrass. The Golf Superintendent. 35(5):]0, l4, 17, 4546.

Evans, T. W. 1932. Renovating golf greens; some practical suggestions for
greenkeepers. The J. Board Greenkeeping Res. 2(6):]81-182.

Freund, T.W., and W.J. Wilson. 1993. Statistical Methods. Academic Press, Inc., San
Diego, CA.

Johnson, B. J. 1987. Effect of core cultivation on preemergence herbicide activity in
bermudagrass. HortSci. 22(3):440-441.

Kerr, CF. 1968. Turf enemy number 1, Poa annua. Weeds Trees and Turf. 7(3):]3-16,
43.

Klute, A. 1965. Laboratory measurement of hydraulic conductivity of saturated soil. p.
210-220. In D.D. Evans (ed.) Methods of Soil Analysis. Part 1. Agron. Monogr. 9.
ASA and SSSA, Madison, WI.

Koch, W. 1968. Environmental factors affecting the germination of some annual
grasses. 9th Brit. Weed Control Conf. 1:14-19.

Murphy, J .A., and PE. Rieke. 1994. High pressure water injection and core cultivation
of a compacted putting green. Agron. J. 86:719-724.

89

90
Radko, A. M. 1980. The USGA Stimpmeter for measuring the speed of putting greens.
Proc. Third Int. Turfgrass Res. Conf. 3:473-476.

Roberts, HA. 1986. Persistence of seeds of some grass species in cultivated soil. Grass
and Forage Sci. 41:273-276.

Roberts, H.A., and ME. Rickettes. 1979. Quantitative relationships between the weed
flora afier cultivation and the seed population in the soil. Weed Res. 19:269-275.

Robinson, B. P. 1952. Stronger grasses, nitrogen, Poa annua answer. Golfdom.
26(7):66-67.

Schery, R. W. 1968. Bluegrass/bentgrass checks Poa annua. The Golf Superintendent.
36(10):32-34.

Schmidt, R. E., and J. F. Shoulders. 1972. Winter turf development on dormant
bermudagrass as influenced by summer cultivation and winter N fertilization. Agron.
J. 64:435-437.

Twombly, AR. 1952. Reduce Poa annua in greens. Golfdom. 26(7):67-69.

Vomocil, J .A. 1965. Pore-size distribution. p. 300-314. In D.D. Evans (ed.) Methods of
Soil Analysis. Part 1. Agron. Monogr. 9. ASA and SSSA, Madison, WI.

Youngner, VB. 1968. Vertical mowing-aerification and Poa annua invasion. Florida
Turf. 1(1): 1 , 6.

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