Effect of Herbicide-Organic Mulch Combinations on Weed Control and Herbicide Persistence ...

167 Pages·2011·1.89 MB·English

Effect of Herbicide-Organic Mulch Combinations on Weed Control and Herbicide
Persistence

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy
in the Graduate School of The Ohio State University

By
Upender Reddy Somireddy, M.Sc.
Graduate Program in Horticulture and Crop Science
******
The Ohio State University
2011

Dissertation Committee:
Professor S. Kent Harrison, Adviser
Professor John Cardina
Professor Mark Bennett
Professor Terrence Graham
Copyright by
Upender Reddy Somireddy
2011
Abstract

Integration of different weed control methods is essential to address the financial
as well as environmental concerns being faced by nursery and landscape industry.
Herbicide and mulch combinations have been suggested to achieve longer weed control
in nurseries and landscapes. Field and laboratory experiments were conducted to
determine the effects of herbicide formulations, mulch materials, depths of mulches, and
herbicide placement relative to mulches on herbicide efficacy and persistence. Two field
experiments were conducted, the first in the fall of 2006 and 2007 and the second in
spring of 2007 and 2008. Granular and liquid formulations of a trifluralin+isoxaben
mixture were applied alone and in combination with pine nuggets and hardwood mulch at
three depths, 3-, 6-, and 12-cm. Granular herbicides were applied alone (without mulch)
and above the mulch; and granular-pretreated mulches were also included. Liquid
herbicides were applied alone, over the mulch, under the mulch, or as herbicide-
pretreated mulches. Trifluralin and isoxaben in all formulations were applied at the rate
of 4.48 kg ai/ha + 1.12 kg ai/ha, respectively. Mulch alone treatments and untreated
control (no mulch, no herbicide) were also included. Visual weed control ratings and
weed fresh weight data were collected at 30, 60, 90, and 120 days after treatment (DAT)
for the spring experiment and at 180 and 210 DAT for the fall experiment. Visual ratings
were based on a scale of 0 (no control) to 10 (complete control), with 7 and above being
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commercially acceptable. Selected treatments from the spring experiment, including the
granular formulation alone, the liquid formulation alone, liquid formulation applied under
6-cm mulches, and the liquid formulation-treated mulches at 6-cm were used to
investigate herbicide persistence. Herbicide residue analysis using liquid chromatography
and bioassay studies using oats and radish were part of the herbicide persistence studies.
All the treatments involving 6-cm and 12-cm mulch with or without herbicides provided
efficacy ratings of above 7 in both experiments. Certain combinations of 3-cm mulch and
herbicides, such as granular formulation over 3-cm pine nuggets, liquid formulation
under 3-cm pine nuggets, and liquid formulation under 3-cm hardwood consistently
provided at efficacy ratings ≥ 7 at all evaluation dates in both studies. This could be due
to the longer residual activity of herbicides in those treatments. The time-course assay of
herbicide dissipation in soil indicated that herbicides applied under the mulch persisted
longer compared to herbicides applied alone. Results suggested that the persistence of
herbicides largely depended on the physico-chemical properties of herbicides and
mulches, as well as soil moisture and temperature. Weed control with greater mulch
thickness could be largely due to the physical inhibition of weed germination and growth
by the mulch, whereas at lower mulch thickness, the addition of herbicides to the mulch
treatments was necessary to provide weed control equivalent to the thick mulch layer.
Mulches applied at the 12-cm depth are expensive and can be detrimental to health of
desirable plants, even though it provided almost complete weed control. Depth of
mulches could be reduced to 3-cm from commercially recommended depths of 5- to 8-cm
when herbicides were combined with mulches.
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Acknowledgements

I would like to thank my advisor Dr. S. Kent Harrison for his invaluable guidance
and intellectual support. I would like to thank Dr. John Cardina for the encouragement
and guidance to finish my Ph.D. program. It is not possible without the help, support and
guidance of Drs. Harrison and Cardina. I would like to thank Dr. Terry Graham for
agreeing to serve as committee member and helping me in herbicide residue analysis.
Thanks to Dr. Mark Bennett for agreeing to serve as committee member and providing
feedback on my dissertation.

I would like to express my sincere gratitude to Dr. Hannah Mathers for giving me
opportunity to pursue Ph.D. program and providing me guidance and financial support.
My special thanks to Mathers lab members: Luke Case and Kyle Daniel for their help in
set up field experiments as well as in data analysis. I would also like to thank other
current and former members of Mathers lab, Alejendra Acuna, Dania Rivera, Jason
Parish, Cheryl, Denise Johnson, Phoebe Gordon, and Michele Bigger. I would also like to
thank Tara Daniel for the constant encouragement and support during my Ph.D. program.

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Thanks to Mark and Glenn of Waterman farm, and green house coordinators,
Dave and Jim for their help in field and green house studies. I would also like to thank
Elaine Grassbaugh for her help in my bioassay study, and Sourav Chakraborty, Stephen
Opiyo, and Jiye Chang of plant pathology department for their help with chemical
analysis.

I would also like to thank Dr. David Gardener and his lab group, Aneta
Studzinska and Ed Nangle for their help and support with herbicide extraction. I am also
thankful to rest of the HCS faculty, staff and students who made my stay at OSU more
enjoyable and less painful.

Finally, I would like to thank my family and friends for their constant support and
encouragement to successfully finish my studies at OSU.

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Vita

2000 ............................................................ B.Sc. Agriculture. A.N.G.R. Agricultural
University, Hyderabad, India
2003 ............................................................ M.Sc. Agronomy, A.N.G.R. Agricultural
University, Hyderabad, India
2004 ............................................................ Farm Supervisor, Mahyco Research
Foundation, Hyderabad, India
2005 ............................................................ Junior Research Fellow, A.N.G.R.
Agricultural University, Hyderabad, India

2006 ............................................................ Production Executive, Monsanto India Ltd.
Sathupally, Khammam, India

June, 2006 to present ................................... Graduate Research Associate, Department
of Horticulture and Crop Science, The Ohio
State University

Fields of Study

Major Field: Horticulture and Crop Science

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Table of Contents
Page #

Abstract…………………………………………………...…………………….................ii
Acknowledgements……………………………………………………….……………....iv
Vita……………………………………………………………………………………......vi
List of Tables……………………………………………………………………...…….. ix
List of Figures……………………………………………………………………………..x
Chapter 1: Literature Review
Impacts of weeds on crop production……………………………………..1
Weed management methods……………………………………............... 3
Herbicide disadvantages…………………………………………. ………9
New innovations for weed management…………………………. ……..14
Organic mulches………………………………………………….……...18
Allelopathy……………………………………………………………… 21
Herbicide and mulch combinations…………………………………….. 22
Literature Cited……………...…………….……………………………..27

Chapter 2: Effect of spring applied herbicide-organic mulch combinations
on weed control

Introduction………………………………………………………………38
Materials and Methods…………………………………………………...44
Results and Discussion…………………………………………………..46

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Page #

Literature Cited…………………………………………………………………..70

Chapter 3: Effect of fall applied herbicide-organic mulch combinations on
weed control

Introduction………………………………………………………………74
Materials and Methods…………………………………………………...80
Results and Discussion…………………………………………………..83
Literature Cited…………………………………………………………..96

Chapter 4: Effect of herbicide-organic mulch combinations on herbicide
persistence in soil

Introduction……………………………….…………………………….102
Materials and Methods……………………………………………….…105
Results and Discussion…………………………………………………111
Literature Cited…………………………………………………………127

Chapter 5: Summary and conclusions………………………………………………….131

Literature Cited…………………………………………………………………………135

Appendix A: Wooden boxes used to treat mulches…………………………………….153
Appendix B: Wooden boxes used to apply mulches in the field……………………….154
Appendix C: Resulsts of orthogonal analysis for spring……………………………….155
Appendix D: Resulsts of orthogonal analysis for fall…………………………………..156

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List of Tables

Table Page #
1.1 Preemergence herbicides labeled for weed control in
ornamental crops (Kuhns et al. 2007)……………………………………………..7

2.1 Weed fresh weight (g) and visual ratings of herbicide, mulch, and
herbicide-mulch combined treatments in 2007 and 2008…………………….…58

2.2 Weed fresh weight (g) and visual ratings of herbicide, mulch, and
herbicide-mulch combined treatments in 2007 and 2008……………………..…60

2.3 Weed fresh weights (g) of herbicide, mulch, and herbicide-mulch
combined treatments at different DAT in 2008………………………………….62

2.4 Efficacy ratings of herbicide, mulch, and herbicide-mulch combined
treatments at different days after treatments (DAT) in 2007…………………….64

2.5 Weed fresh weights (g) of herbicide, mulch, and herbicide-mulch
combined treatments at different DAT in 2007……………...……..……………66

3.1 Weed efficacy ratings of fall applied mulch, herbicide, and mulch
and herbicide combined treatments for experiments initiated
in fall 2006 and 2007…………………………………………………………….92

3.2 Weed fresh weights (g) of fall applied mulch, herbicide, and mulch
and herbicide combined treatments for experiments initiated
in fall 2006 and 2007…………………………………………………….………94

4.1 Parameter values from exponential decay and sigmoid growth
curves…………………………………………………………………...………126

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