Integrated Management of Dollar Spot Disease of Creeping Bentgrass Using Soil Conditioners

Eslin Duygu Oztur

A Thesis

presented to

The University of Guelph

In partial fulfilment of requirements for the degree of

Master of Science

Plant Agriculture

Guelph, Ontario, Canada

ABSTRACT

INTEGRATED MANAGEMENT OF DOLLAR SPOT DISEASE OF CREEPING BENTGRASS USING SOIL CONDITIONERS

Eslin Duygu Oztur Advisor: University of Guelph, 2020 Dr. Katerina Serlemitsos Jordan

Dollar spot, caused by the fungus Clarireedia jacksonii, can lead to considerable damage to creeping bentgrass (Agrostis stolonifera L.) on golf course greens. This one-year study assessed management strategies that integrated soil conditioners

(fish emulsion, fish hydrolysate, worm castings, and spent mushroom compost) with a rolling treatment to reduce dollar spot severity. None of the soil conditioners reduced dollar spot in the greenhouse or field studies, nor was there any improvement in turf color, clippings, root dry weight or tissue N content. The rolling treatment had a significant effect on turf color and reduced dollar spot severity at one location and only when disease pressure was high. The results indicated that the use of soil conditioners would not be a recommended practice for dollar spot when disease pressure is high but rolling could be included as a management practice to suppress dollar spot.

DEDICATION

I dedicate this thesis to my beloved mother Aysegul Kivanc, whose profound love, support and encouragement made it possible for me to complete this work. I admire the effort and sacrifice you made for my career in supporting my study abroad. You gave me the strength to make it through another day. Without you and your support, I would not have had the perseverance I needed to achieve this challenge.

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ACKNOWLEDGEMENTS

I am grateful to everyone who supported me during my tough times here in Canada. Firstly, I’d like to thank my advisor Katerina Serlemitsos Jordan who accepted me as a Master’s student and gave me this opportunity to pursue my dreams in Plant Pathology. Her teaching style and immense knowledge of plant pathology made a strong impression on me and I move forward carrying positive memories with me. Her guidance helped me throughout my research and writing process of this thesis. I would like to again express my profound gratitude to my advisor that her door was always open to me whenever I ran into trouble as a self-funded student.

Special thanks to John Watson for his invaluable assistance in the field, advising me on calculations and data collection during the experiment stage of my study. His guidance, recommendations and comments during the study are whole-heartedly appreciated as he enabled me to learn the ropes of scientific research. I am also appreciative of his patience.

I am also grateful to all of my lab group with whom I had pleasure to work; Karen Francisco, Vighnesh Sukhu, Conor Russell and Clyde Yan.

I would also like to thank my committee members, Eric Lyons and Cheryl Trueman for their valuable guidance and input for this project.

I would like to express my deepest appreciation to Michelle Edwards who helped me to understand statistics during my study and I could not have done the analyses without her assistance.

I would also like to thank Dr. Tevfik Inan for his endless patience to support me through the compilation process of my thesis

Lastly, very special thanks to my family; my mom, my dad, my grandma and my aunt for their total support through video calls all days and nights. Even though we were so far away from each other, you were always close to my heart.

TABLE OF CONTENTS

1 İçindekiler

ABSTRACT ...... ii

DEDICATION ...... iii

ACKNOWLEDGEMENTS ...... iv

TABLE OF CONTENTS ...... v

LIST OF TABLES ...... viii

LIST OF FIGURES ...... x

LIST OF ABBREVATIONS AND ACRONYMS ...... xiii

LIST OF APPENDICES ...... xiv

1 Review of Literature...... 1

1.1 General Introduction...... 1

1.2 Importance of the Turfgrass Industry ...... 3

1.3 Creeping Bentgrass ...... 4

1.4 Dollar Spot Disease ...... 4

1.4.1 Biology of Dollar Spot Pathogen ...... 5

1.4.2 Epidemiology and Disease Cycle ...... 7

1.5 Symptomology of Dollar Spot ...... 8

1.6 Management of Dollar Spot ...... 9

1.6.1 Host Resistance ...... 9

1.6.2 Chemical Control ...... 9

1.6.3 Cultural Control ...... 11

1.6.4 Biological Control ...... 15

1.7 Organic Fertilizers and Soil Conditioners ...... 18

1.8 The Effect of Soil Quality and Health on Disease Suppression ...... 24

1.9 Project Rationale ...... 27

1.10 Research Hypothesis and Objectives ...... 29

2 Materials and Methods ...... 30

2.1 Greenhouse Studies ...... 30

2.1.1 Preparation and Growth Conditions of Plants Materials...... 30

2.1.2 Experimental Design...... 32

2.1.3 Preparation and Application of Soil Conditioners ...... 32

2.1.4 Fungicide Application...... 37

2.1.5 Pathogen Inoculum Preparation ...... 37

2.1.6 Inoculation Protocol ...... 38

2.1.7 Data Collection...... 40

2.1.8 Statistical Analyses ...... 42

2.2 Field Studies ...... 43

2.2.1 Site Descriptions ...... 43

2.2.2 Preparation and Application of Soil Conditioners ...... 43

3 Results ...... 50

3.1 Greenhouse Study 1 ...... 50

3.1.1 The Effects of Soil Conditioner Treatments on Dollar Spot Severity ....50

3.1.2 The Effects of Soil Conditioner Treatment on AUDPC ...... 52

3.1.3 The Effects of Soil Conditioner Treatments on Turf Color ...... 52

3.1.4 The Effects of Soil Conditioners on Root Dry Weight ...... 55

3.1.5 The Effects of Soil Conditioners on Clipping Yield ...... 57

3.1.6 The Effects of Soil Conditioner Treatments on Tissue Nitrogen Concentration of Creeping Bentgrass ...... 58

3.2 Greenhouse Study 2 ...... 60

3.2.1 The Effects of Soil Conditioner Treatments on Dollar Spot Severity ....60

3.2.2 The Effects of Soil Conditioner Treatments on AUDPC ...... 63

3.2.3 The Effect of Soil Conditioner Treatments on Turf Color ...... 64

3.2.4 The Effects of Soil Conditioners on Root Dry Weight ...... 66

3.2.5 The Effects of Soil Conditioner Treatments on Clipping Yield ...... 68

3.2.6 The Effects of Soil Conditioner Treatments on Tissue Nitrogen Concentration of Creeping Bentgrass ...... 69

3.3 Field Study 1 ...... 71

3.3.1 GRS 1 (Guelph Research Station 1) Trial...... 71

3.4 Field Study 2 ...... 79

3.4.1 GRS 2 (Guelph Research Station 2) Trial...... 79

4 Discussion...... 89

4.1 Greenhouse Studies ...... 89

4.1.1 Field Studies ...... 95

5 Conclusion ...... 102

REFERENCES...... 106

APPENDICES ...... 128

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LIST OF TABLES

Table 2.1: Chemical and physical analyses of fertilizer treatments ...... 35

Table 2.2: Application rates for soil conditioner treatments in the first and second greenhouse study for 14-week period, 2019...... 36

Table 2.3: Application rates of soil conditioner treatments in field studies, 2019...... 45

Table 3.1: The effects of soil conditioner treatments on dollar spot severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 ...... 51

Table 3.2: The effect of soil conditioner treatments on turf color severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height of cut (6mm) in GH Study 1 in Guelph, ON, in 2019 ...... 54

Table 3.3: The effects of soil conditioner treatments on root dry weight (ash free) in the 0-5, 5-10 and 10 + cm depth in creeping bentgrass ‘Penn A-4’ grown on 100:0 sand-based root zone maintained as fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 ...... 56

Table 3.4 The effects of soil conditioners on dollar spot severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height (6mm) in GH study 2 in Guelph, ON, in 2019 ...... 62

Table 3.5 : The effects of soil conditioner treatments on turf color severity in ‘Penn A- 4’ creeping bentgrass maintained at fairway height (6mm) in GH study 2 in Guelph, ON, in 2019 ...... 65

Table 3.6 :The effects of soil conditioner treatments on root dry weight (as free) in the 0-5 cm, 5-10 and 10+ cm depth in creeping bentgrass ‘Penn A-4’ grown on 100:0 sand-based rootzone maintained as fairway height of cut (6mm) in GH study 2 in Guelph, ON, in 2019 ...... 67

Table 3.7: The effects of soil conditioner treatments on dollar spot severity in ‘Penn A-4’ creeping bentgrass putting greens at the GUELPH RESEARCH STATION 1 location, Guelph, ON, in 2019 ...... 73

Table 3.8: The effects of soil conditioner treatments on turf color in ‘Penn A-4’ creeping bentgrass putting greens at the GUELPH RESEARCH STATION 1 location in Guelph, ON, in 2019 ...... 76

Table 3.9: The effects of soil conditioner treatments on Normalized Difference Vegetation Index (NDVI) in creeping bentgrass ‘Penn A-4’ putting greens at GUELPH RESEARCH STATION 1 location, in Guelph, ON, in 2019 ...... 78

Table 3.10: The effects of soil conditioner treatments on dollar spot severity in ‘007’ putting greens at GUELPH RESEARCH STATION 2 location, Guelph, ON, in 2019 ...... 81

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Table 3.11: The effect of soil conditioner treatments on turf color in ‘007’ creeping bentgrass putting greens at GUELPH RESEARCH STATION 2 location in Guelph, ON, in 2019 ...... 86

Table 3.12: The effects of soil conditioner treatments on Normalized Difference Vegetation Index (NDVI) in creeping bentgrass ‘007’ putting green at GUELPH RESEARCH STATION 2 location in Guelph, ON, in 2019 ...... 87

LIST OF FIGURES

Figure 2.1: A) Seeding creeping bentgrass in 100:0 (%100 sand and 0% soil) sand root zone material in PVC tube, B) Mixing creeping bentgrass seed with siliceous sand, C) Top dressing the creeping bentgrass seed filled with 100:0 siliceous sand, D) Preparation of seedbed by lightly rolling each pot ...... 31

Figure 2.2: Brewing Aerated Worm Casting Tea ...... 32

Figure 2.3: Drying Kentucky Bluegrass seed inoculated with C. jacksonii in a laminar flow hood for 48 h ...... 38

Figure 2.4: Sprinkling seed inoculum on the surface of the pot using scoopula...... 39

Figure 2.5: C. jacksonii infested seeds on the surface of the pots ...... 39

Figure 2.6: PVC tubes covered with the resealable bags ...... 40

Figure 2.7: The first visible white cottony mycelium on the leaf blades of creeping bentgrass, one week after inoculation ...... 42

Figure 3.1: The effects of soil conditioners on area under disease progress curve (AUDPC) on dollar spot disease on creeping bentgrass ‘Penn A-4’ maintained at fairway height of cut (6mm) for rating between July 3 to August 14 in first greenhouse study in Guelph, ON, in 2019. Pots were inoculated with C. jacksonii on June 25 and the first symptoms began to appear on July 3. AUDPC was calculated for each treatment using the equation: AUDPC = Σni-1i=1 ([yi + y(i + 1)] / 2) (t(i+1) - ti), where i is the order index for the times, and ni is the number of times (Campbell and Madden, 1990). Chlorothalonil was applied the day before the soil conditioner applications with 14 days intervals. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05)...... 52

Figure 3.2: The effects of soil conditioner treatments on dry weight of clippings in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019. The application of soil conditioner treatments began on 14 May, then pots were inoculated with C. jacksonii on 25 June. The clippings were collected at the end of the study on 22 August 2019. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05)...... 57

Figure 3.3: The relationship between tissue N concentration and clipping dry weight of creeping bentgrass ‘Penn A-4’ maintained as fairways height of cut (6mm) in GH 1 in Guelph, ON, in 2019...... 58

Figure 3.4: The effects of soil conditioners on N leaf tissue concentration of creeping bentgrass ‘Penn A-4’ clippings maintained as fairways height of cut (6mm) in GH 1 in Guelph, ON, in 2019. The clippings were collected in the end of the study. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method. (≤0.05) ...... 59

Figure 3.5: The relationship between tissue N concentration and AUDPC of creeping bentgrass ‘Penn A-4’ maintained as fairways height of cut (6mm) in GH 1 in Guelph, ON, in 2019...... 60

Figure 3.6: The effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) for rating between 30 September and 11 November in GH study 2 in Guelph, ON, in 2019. Pots were inoculated with C. jacksonii on 23 September and the first symptoms began to appear on 30 September. AUDPC was calculated for each treatment using the equation: AUDPC = Σni-1i=1 ([yi + y (i + 1)] / 2) (ti+1) - ti), where yi is the disease severity at the ith rating date, ti is the day of the ith rating and n is the total number of evaluation (Campbell and Madden, 1990). Chlorothalonil was applied the day before the soil conditioner treatments at 14-day intervals. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05) ...... 63

Figure 3.7: The effects of soil conditioner treatments on dry weight of clippings in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) in GH study 2 in Guelph, ON, in 2019.The application of soil conditioner treatments began on 12 August, then pots were inoculated with C. jacksonii on September 23. The clippings were collected at the end of the study on 12 November. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05)...... 68

Figure 3.8: The relationship between tissue N concentration and clipping dry weight of creeping bentgrass ‘PennA-4’ maintained as fairways height of cut (6mm) in GH 2 in Guelph, ON, in 2019...... 69

Figure 3.9: The effects of soil conditioner treatments on N leaf tissue content of creeping bentgrass ‘Penn A-4’ clippings maintained as fairway height of cut (6mm) in GH 2 study in Guelph, ON, in 2019. The clippings were collected in the end of the study. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05) ...... 70

Figure 3.10: The relationship between tissue N concentration and AUDPC dollar spot on creeping bentgrass ‘Penn A-4’ maintained as fairways height of cut (6mm) in GH 2 in Guelph, ON, in 2019...... 71

Figure 3.11: The effects of soil conditioner treatments on area under disease progress curve (AUDPC) of dollar spot disease in creeping bentgrass ‘Penn A-4’ for rating between 2 August and 13 September at the GUELPH RESEARCH STATION 1 location in Guelph, ON, in 2019. Plots were inoculated with C. jacksonii on 23 July and the first symptoms began to appear on 2 August. AUDPC was calculated for each treatment using the equation: AUDPC = Σni-1i=1 ([yi + y(i + 1)] / 2) (ti+1) - ti), where yi is the disease severity at the ith rating date, ti is the day of the ith rating and n is the total number of evaluation (Campbell and Madden, 1990). Vertical bars represent the standard errors of the mean. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05) ...... 74

Figure 3.12: The effects of rolling treatment across days affected by soil conditioner treatments on dollar spot severity in creeping bentgrass ‘007’ putting greens at GUELPH RESEARCH STATION 2 location, Guelph, ON, in 2019. Rolling was performed 3x week (Monday, Wednesday and Friday), started on 8 August after inoculation and ended on 14 September in 2019. Plots were inoculated with C. jacksonii on 23 July. 10 DAI refers to 2 August. Bars with the same letter for each soil conditioner treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05)...... 82

Figure 3.13: The effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot disease in creeping bentgrass ‘007’ for rating between 2 August and 13 September at GUELPH RESEARCH STATION 2 location in Guelph, ON, in 2019. Plots were inoculated with C. jacksonii on 23 July and the first symptoms began to appear on 2 August. AUDPC was calculated for each treatment using the equation: AUDPC = Σni-1i=1 ([yi + y (i + 1)] / 2) (ti+1) - ti), where yi is the disease severity at the ith rating date, ti is the day of the ith rating and n is the total number of evaluation (Campbell and Madden, 1990). Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05)...... 83

Figure 3.14: The effects of rolling treatment in creeping bentgrass ‘007’ turf color at GUELPH RESEARCH STATION 2 location in Guelph, ON, in 2019. Rolling performed 3x week (Monday, Wednesday and Friday) was started on 8 August after inoculation and ended on 14 September in 2019. Plots were inoculated with C. jacksonii on 23 July. The turf color was visually rated on the estimation scale, with 9 representing the darkest green color, 6=minimum acceptable color, 1= completely straw-brown color turf using National Turfgrass Evaluation Protocol (NTEP) rating system. Bars with the same letter for each soil conditioner treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05)...... 84

Figure 3.15: The effects of rolling treatment on NDVI values in creeping bentgrass ‘007’ on each rating dates at GUELPH RESEARCH STATION 2. The arrows show the significant rolling treatment effect. Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) ...... 88

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LIST OF ABBREVATIONS AND ACRONYMS a.i.- active ingredient

AUDPC - area under disease progress curve

ANOVA - analyses of variance

AWCT- aerated worm casting tea

DAI - days after inoculation

DI - deionized water

FE - fish emulsion

FH - fish hydrolysate

GH= greenhouse

GRS - Guelph Research Station

LOI - loss on ignition

N - nitrogen

NTEP - National Turfgrass Evaluation Protocol

NDVI= Normalized Difference Vegetation Index

PVC - polyvinyl chloride

PDA - potato dextrose agar

SMC - spent mushroom compost

SOM - soil organic matter

USGA - United States Golf Association

WC - worm castings

WIN= water insoluble nitrogen

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LIST OF APPENDICES

Appendix Table A1. 1: Proc mixed variance analyses results of the effects of soil conditioner treatments on dollar spot severity in creeping bengtrass ‘Penn A-4’ maintained at fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 .. 128

Appendix Table A1. 2: Proc mixed variance analyses results of the effects of soil conditioner treatments on turf color in creeping bengtrass ‘Penn A-4’ maintained at fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 ...... 128

Appendix Table A1. 3: Proc mixed variance analyses results of the effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot in creeping bentgrass ‘Penn A-4’ maintained at fairway height of cut (6mm) in GH study 1, Guelph, ON in 2019 ...... 128

Appendix Table A1. 4 :Proc mixed variance analyses results of the effects of soil conditioner on dry weight of clippings in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 ...... 128

Appendix Table A1. 5 : Proc mixed variance analyses results of the effects of soil conditioner treatments on root dry weight (ash free) in the 0-5, 5-10 and 10 + cm depth in creeping bentgrass ‘Penn A-4’ grown on 100:0 sand-based root zone maintained as fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 . 129

Appendix Table A1. 6 :Proc mixed variance analyses results of the effects of soil conditioner on N leaf tissue content of creeping bentgrass ‘Penn A-4’ clippings maintained as fairways height of cut (6mm) in GH study 1 in Guelph, ON, in 2019 129

Appendix Table B2. 1: Proc mixed variance analyses results of the soil conditioner treatments on dollar spot severity in creeping bengtrass ‘Penn A-4’maintained at fairway height (6mm) in GH study 2 in Guelph, ON, in 2019 ...... 130

Appendix Table B2. 2 :Proc mixed variance analyses results of the effects of soil conditioner treatments of creeping bentgrass ‘Penn A-4’on turf color on fairways in GH study 2, Guelph, ON in 2019 ...... 130

Appendix Table B2. 3: Proc mixed analyses results of the effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot in creeping bentgrass ‘Penn A-4’maintained as fairway height of cut (6mm) in GH study 2, Guelph, ON in 2019 ...... 130

Appendix Table B2. 4: Proc mixed variance analyses results of the effects of soil conditioner treatments on dry weight of clippings in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) in GH study 2 in Guelph, ON, in 2019 . 131

Appendix Table B2. 5: Proc mixed variance analyses results of the effects of soil conditioner treatments on root dry weight (ash free) in the 0-5 cm, 5-10 cm and 10+ cm depth in creeping bentgrass ‘Penn A-4’ grown on 100:0 sand-based root zone maintained as fairway height of cut (6mm) in GH study 2 in Guelph, ON, in 2019 . 131

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Appendix Table B2. 6: Proc mixed variance analyses results of the effects of soil conditioner treatments on N leaf tissue content of creeping bentgrass ‘Penn A-4’ clippings maintained as fairway height of cut (6mm) in GH study 2 in Guelph, ON, in 2019...... 131

Appendix Table C3. 1: Proc mixed variance analyses results of the effects of soil conditioner treatments on dollar spot severity in creeping bengtrass ‘Penn A-4’putting greens at GUELPH RESEARCH STATION 1, Guelph, ON, in 2019 ...... 132

Appendix Table C3. 2: Proc mixed variance analyses results of the effects of soil conditioner treatments on turf color in creeping bengtrass ‘Penn A-4’color putting greens at GUELPH RESEARCH STATION 1 in Guelph, ON, in 2019 ...... 132

Appendix Table C3. 3: Proc mixed variance analyses results of the effects of soil conditioner treatments on area under disease progress curve (AUDPC) in creeping bentgrass ‘Penn A-4’at GUELPH RESEARCH STATION 1 putting greens, Guelph, ON in 2019 ...... 133

Appendix Table C3. 4: Proc mixed variance analyses results of the effects of soil conditioner treatments on NDVI (Normalized Difference Vegetation Index) in creeping bentgrass ‘Penn A-4’putting greens at GUELPH RESEARCH STATION 1 in Guelph, ON, in 2019 ...... 133

Appendix Table C3. 5: Proc mixed variance analyses of the effects of soil conditioner treatments on Soil Organic Matter (SOM) in creeping bentgrass ‘Penn A- 4’at GUELPH RESEARCH STATION 1 putting greens, Guelph, ON in 2019 ...... 134

Appendix Table C3. 6: Proc mixed variance analyses of the effects of soil conditioner treatments on Soil Aggregate Stability in creeping bentgrass ‘Penn A-4’at GUELPH RESEARCH STATION 1 putting greens, Guelph, ON in 2019 ...... 134

Appendix Table D4. 1: Proc mixed variance results of the effects of soil conditioner treatments on dollar spot severity in creeping bentgrass ‘007’ at GUELPH RESEARCH STATION 2 putting greens, Guelph, ON, in 2019 ...... 135

Appendix Table D4. 2: Proc mixed variance results of the effects of soil conditioner treatments on turf color in creeping bengtrass ‘007’ putting greens at GUELPH RESEARCH STATION 2 in Guelph, ON, in 2019...... 135

Appendix Table D4. 3: Proc mixed variance results of the effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot disease in creeping bentgrass ‘007’ at GUELPH RESEARCH STATION 2 putting greens, Guelph, ON in 2019 ...... 136

Appendix Table D4. 4: Proc mixed variance analyses of the effects of soil conditioner treatments on NDVI (Normalized Difference Vegetation Index) in creeping bentgrass ‘007’ at GUELPH RESEARCH STATION 2 putting greens, Guelph, ON, in 2019 ...... 136

Appendix Table D4. 5: Proc mixed variance analyses of the effects of soil conditioner treatments on Soil Organic Matter (SOM) in creeping bentgrass ‘007’ at GUELPH RESEARCH STATION 2 putting greens, Guelph, ON, in 2019 ...... 137

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1 Review of Literature

1.1 General Introduction

Dollar spot is a destructive fungal disease that is known to attack most turfgrass species, particularly creeping bentgrass (Agrostis stolonifera L.), on golf course putting-greens, bowling greens, closely mown fairways, and home lawns. Dollar spot, which is considered to be the most economically significant turfgrass disease in Canada and the United States (Powell et al., 2000), causes high risks and maintenance costs for both cool- and warm-season turfgrass species (Smiley et al., 2005). The causal pathogen of the disease was formerly named as Sclerotinia homoeocarpa F. T. Bennett (Bennett, 1937; Dernoeden, 2013; Goodman and Burpee, 1991); however, recent research on the genetic identity of the pathogen has caused dollar spot to be reclassified as a new genus, Clarireedia gen. nov. Clarireedia jacksonii C. Salgado, L.A. Beirn, B.B. Clarke, & J.A. Crouch sp. nov. is one of the four Clarireedia species designated and causes dollar spot disease on C3 grass hosts around the globe (Aynardi, et al., 2019; Salgado-Salazar et al., 2018).

The fungus survives in infected grass tissues and is distributed locally when mycelium grows from a diseased leaf to a healthy leaf (Fenstermacher, 1980; Walsh et al., 1999). Salgado-Salazar et al. (2018, p.769) give the morphological description of C. jacksonii as “colonies fast-growing, cottony, front white to off-white with light brown spots, back white to off-white, later collapsing and turning tan to brown”.

In Ontario, disease progress is accelerated by high humidity and temperatures above 20 ˚C (Kerns, 2018). The dollar spot fungus overwinters as dormant mycelium in infected plants or as stromata formed on the lesions from previous epidemics. When conducive conditions such as continuous leaf wetness and night temperatures of over 10 ˚C occur, the fungus grows on the surface to penetrate the leaf blade (Walker, 2017).

Turfgrass is subject to various management practices, including irrigation, mowing, and the use of fungicides, insecticides, and fertilizers (Jo et al., 2008). Although there are various cultural management methods of dollar spot such as providing turf with sufficient nitrogen fertility, displacing leaf wetness, and planting

resistant cultivars (Putman & Kaminski, 2011), the most successful strategy for dollar spot management has been the application of chemical fungicides, which are often required throughout the growing season (Walsh et al., 1999). However, these frequent fungicide inputs have resulted in resistance of the pathogen to various groups of chemicals (Detweiler et al., 1983; Warren et al., 1974). The use of pesticides is also discouraged because of environmental concerns, various health risks, and additional costs (Boulter et al., 2002; Zhou & Boland, 1998). More money is spent on chemicals to manage dollar spot than any other turf diseases (“Dollar Spot of Turfgrasses in Georgia: Identification and Control”, 2016). In southern Ontario and the United States, the annual cost of fungicide applications often exceeds $170 per ha, making management of dollar spot more costly than any other disease on golf courses (Goodman & Burpee, 1991; Zhou & Boland, 1998).

Several biological control strategies have been investigated, including the fungal and bacterial, and these have been shown to be less effective than fungicides. Many natural products such as composts, sewage sludge, organic fertilizers and manure-based preparations are colonized by mixtures of microorganisms that restrict the development of the disease pathogens (Kenna & Snow, 1999). The applications of antagonistic, sewage sludge materials, natural organic fertilizers and manure composts in field studies have indicated inconsistent results for the reduction of dollar spot in creeping bentgrass (Couch, 1995; Goodman & Burpee, 1991; Kenna & Snow, 1999). Top-dressing with compost has also been shown to suppress dollar spot, depending on the rate of application and type of compost though the efficacy of this method varied considerably (Noble & Coventry, 2005; Walsh et al., 1999).

In addition, composts have been used successfully to provide faster turfgrass establishment, improved color, increased rooting, and less need for fertilizer and irrigation (Landschoot, 1996). Spent mushroom compost containing antagonistic microorganisms that interfere with the activity of plant pathogens (Davis et al., 2005) and the applications of spent mushroom compost on turfgrass have resulted in an increase in soil water retention and a decrease in surface hardness (Landschoot, 2016). Fertilization with organic amendments is associated with increased soil nutrient statues and organic matter (Liang et al., 2012). As a result of this, soil

amendments enhance soil microbial activity (Gomiero et al., 2011). Composts have been shown to add active microbial components to soils and to activate the microbes already present in the soil (Nelson, 1996).

Nitrogen fertility management and dew displacement are considered key cultural management practices for suppressing dollar spot (Dernoeden, 2013). Nitrogen deficiency is an important contributing factor to the prevalence of dollar spot, and fertilizing is one of the cultural practices that can diminish its severity (Christians, 2011). In one study, activated sewage sludge suppressed the dollar spot pathogen more effectively than inorganic nitrogen sources (Nelson and Boehm, 2002). Ultimately, combining cultural practices into a fungicide program is expected to provide an effective disease management (Dernoeden, 2013).

The intensive search for the reduced reliance on synthetic pesticides has led to the development of alternative amendments to be used in disease suppression. For example, the use of by-products from the fish industry have proven to be beneficial for plant health and growth (Abbasi, 2011) and amending soils with fish meal or fish waste has been reported to suppress pathogen populations (Akhtar and Mahmood, 1995; Wilhelm, 1951). The application of fish emulsion has also been reported to provide more than 90% control of cucumber damping-off disease caused by Rhizoctonia solani and Pythium aphanidermatum (Abbasi et al., 2004).

To date, various degrees of beneficial effects of soil amendments, conditioners and fertilizers on suppression of dollar spot in turfgrass have been identified. Yet, further investigation into the use of these products is in strong demand to determine more cost-effective, self-sustaining and environmentally-friendly management tools and strategies for managing turfgrass diseases (Walsh et al., 1999).

1.2 Importance of the Turfgrass Industry

The establishment of lawn area called greens in European villages dates back to Middle Ages; however, the modern turfgrass industry began to expand as the industrial development in the United States after World War II resulted in a rapid growth in the economy (Emmons and Ross, 2014 p.2-3). Improved living conditions

allowed people to demand more recreational activities such as golf, which stimulated the development of many turf products in the 1950’s (Emmons and Ross, 2014 p.2- 3). The turfgrass market has developed since then due to a strong demand for environmental benefits, commercial properties and recreation facilities in the urban landscape (Chawla et al., 2018). The turfgrass industry comprises diverse segments and various business and public sector operations (Tsiplova et al., 2008). The turf industry mainly includes athletic fields, golf courses, sod production, lawn care and landscape and golf course architecture (Mathew et al., 2016).

1.3 Creeping Bentgrass

Creeping bentgrass (A. stolonifera L.) is a cool season perennial lawn grass widely used in golf course putting greens, fairways and tees in Canada (Goodman & Burpee, 1991). The optimum mowing height of creeping bentgrass ranges from 3.0 mm to 12.7 mm (Reicher, 2004; Reynolds, 2014). Some cultivars can maintain canopy cover and playability at mowing heights of 2.5 mm (Christians et al., 2017). It is characterized with fine and bright texture, and dense growth due to spreading through stolons (Bonos et al., 2006; Shelton, 2017). New cultivars with tiller higher density have become very popular as they are tolerant of low mowing heights and contribute to decreasing annual bluegrass encroachment due to their aggressive growth habit (Christians et al., 2017).

1.4 Dollar Spot Disease

Dollar spot is a persistent and problematic disease that affects common turfgrass species including Agrostis, Festuca, Lolium, Poa, Cynodon, and Zoysia genera grown for golf courses sport fields and residential lawns (Smiley et al., 2005).

As Smith et al. (1989) state, the prevalence of high humidity, heavy dew promoted by cool nights, and a temperature range of 15 to 25˚C favor dollar spot outbreaks. Creeping bentgrass is predominantly used on golf courses due to its dense growth, high quality playing surface and its tolerance to low mowing (Jones et al., 2007; Sheared, n. d.). Most Canadian turfgrass managers rely on repeated applications of fungicides to manage dollar spot (Nelson & Boehm, 2002). However, replacing fungicides with more sustainable alternatives has been suggested because

of environmental and health concerns, development of resistant pathogen populations, and low budgets of golf facilities that are severely influenced by fungicide costs they have to spend on controlling dollar spot (Boulter et al., 2002). For an 18-hole golf course with 10-12 ha of fairways, the cost of a single preventative fungicide application ($2,000 to $5,000) is almost equal to the cost of golf course maintenance of each year including labour and material such as top dressing (Moeller, 2014). In the northern United States, golf courses invest 60 to 75 percent of their budget in disease management (Mulhollem, 2018).

1.4.1 Biology of Dollar Spot Pathogen

Recent studies on identification and characterization of the fungus have documented the reclassification of the fungus (Salgado-Salazar et al., 2018) since it was first described by Bennet (1937). Dollar spot was first reported in 1927 by John Monteith who referred to it as ‘small brown patch’ and defined symptoms as straw- colored spots that are not larger than a silver dollar (Monteith, 1927). To avoid the confusion with ‘large brown patch’ which is caused by the fungus Rhizoctonia solani, the disease was later renamed as ‘dollar spot’ (Monteith & Dahl, 1932). The causal agent of dollar spot was identified as a Rhizoctonia monteithiana, a new species, by Bennett (Bennet, 1935); however, two years later, based on further investigations, the fungus was described as the ascomycete Sclerotinia homoeocarpa (Bennet, 1937). Four isolate types were identified: namely, one ‘perfect strain’, producing ascospores and conidia, one ‘ascigerous strain’, producing both ascospores and microconidia, and two ‘non-sporing strains’ (Bennet,1937). After Bennett had classified the fungus in the genus Sclerotinia (Bennett, 1937; Salgado-Salazar et al., 2018), Whetzel (1945) researched on the family of Sclerotinia and reported that the fungi in the genus Sclerotinia produce apothecia from tuberoid sclerotia, a distinctive feature not shared by S. homoeocarpa. It was concluded from this morphological trait that S. homoeocarpa was akin to species such as Rutstroemiaceae and Lambertella (Whetzel, 1945). Nevertheless, Whetzel’s proposition that S. homoeocarpa was a species of Rutstroemia never resulted in reclassification of the fungus (Salgado- Salazar et al., 2018). In the following years, the fungus was reported to exist in the vegetative state without reproductive structures until 1973, when ascospores were observed from S. homoeocarpa isolated from turfgrasses in the UK (Jackson, 1974).

Although the number of Sclerotinia species in the literature exceeded 250 by the end of 1970s, the taxonomic placement of S. homoeocarpa remained confusing and formal classification of the fungus was deferred until 1990s (Kohn, 1979a, 1979b). The molecular technologies used in the 1990s to determine the taxonomic identity of S. homoeocarpa also brought about contradictory outcomes; therefore, the dollar spot fungus was referred to as S. homoeocarpa despite the fact that it does not exhibit the characteristics of a true Sclerotinia species (Salgado-Salazar et al., 2018).

Aiming to resolve the identity of the dollar spot fungus using modern DNA sequence techniques, Salgado-Salazar et al. (2018) found that the fungi that cause dollar spot disease belong to neither the genus Sclerotinia nor Rutstroemia. Their study led to the establishment of a new genus, which described as Clarireedia gen. nov. The data obtained through molecular phylogenetic analyses demonstrated four species within this genus, separated based on their geographic distributions and host preference: C. homoeocarpa comb. nov (United Kingdom), C. bennettii sp. nov. (United Kingdom), C. jacksonii sp. nov. (United States) and C. monteithiana sp. nov. (United States), all of which were found to be capable of causing dollar spot disease (Salgado-Salazar et al., 2018). Salgado-Salazar et al. (2018) report that primarily two Clarireedia species cause disease on the majority of turfgrass species in the United States: C. jacksonii, which is especially virulent on cold-season turfgrass species, and C. monteithiana C. Salgado, L.A. Beirn, B.B. Clarke, & J.A. Crouch sp. nov, which is found on warm-season turfgrass hosts. Aynardi et al. (2019) found that C. jacksonii became more virulent at 25 ˚C and 30 ˚C than C. monteithiana.

Previous and current studies on the pathogens associated with symptoms of dollar spot have widely investigated the diversity of the causal organisms of the disease (Aynardi et al., 2019; Baldwin and Newell, 1992; Espevig et al., 2017; Salgado-Salazar et al., 2018). Although the only official name for the causal agent of dollar spot disease used in the literature until 2018 was Sclerotinia homoeocarpa, we will use the new name Clarireedia jacksonii, the species named by Salgado-Salazar et al. (2018), whose research findings showed that C. jacksonii is one of the most widespread incitants of dollar spot disease with a host preference of creeping bentgrass.

1.4.2 Epidemiology and Disease Cycle

Dollar spot poses a significant threat to many turfgrass species including A. stolonifera (Smiley et al., 2005). Dollar spot occurs in two seasonal epidemics in the northern United States, one from May to late July and the other one from mid-August through October (Powell & Vargas, 2001). The disease can cause an outbreak at almost any time of the year in the southern United States (Dernoeden, 2013). In the Maritimes and Southern Ontario, the disease prevails from early June to late October (Manoharan, 2013).

The ideal temperature range for dollar spot development is from 15˚C to 27˚C; however, maximum pathogenicity occurs when temperatures are between 21˚C and 27˚C and atmospheric humidity is above 85% (Endo, 1963; Walsh et al., 1999). Temperature and prolonged leaf wetness strongly influence infection by dollar spot pathogen (Smiley et al., 2005). The favorable temperatures combined with the long periods of dew or improper irrigation from late afternoon through the evening also increase the chances of the mycelia growth on leaf blades (Shelton, 2017; Smiley et al., 2005). Disease occurrence can also be seen following cool night time temperatures in early and late summer, as this leads to heavy morning dew (Shelton, 2017; Walsh et al., 1999).

The dollar spot fungus overwinters as stromata and as dormant mycelia in infected plant debris (Smiley et al., 2005; Venu et al., 2009). The presence of thatch may be a source of inoculum for pathogen to grow when the conditions are favorable (Smith et al, 1989). Since spore production is believed to be rare or not likely in North America under field conditions, the dissemination of pathogen may be through direct movement of inoculum with the mechanical or physical movement on diseased leaf blades (Horvath et al.; Vargas, 2005; 2007; Walker, 2017). Therefore, the pathogen is distributed through the spread of infected leaf tissues by people, animals, equipment, water or wind (Walker, 2017). In close proximity, the distribution of the pathogen occurs when mycelium grows from infected leaves to healthy leaves. Direct movement of the pathogen through mycelium or spread of infested plant tissues can act as a primary source of inoculum (Horvath, 2009; Vargas, 2005). Following prolonged leaf wetness, a white cobweb-like mycelium develops and can

be distinctly observed in morning dew. At this point, the fungus directly penetrates into the leaf blade and can cause infection that results in the formation of a lesion (Walker, 2017). The penetration occurs either through wounded leaves created by mowing or other factors or through natural openings such as stomata (Smiley et al., 2005). Following penetration, the pathogen secretes oxalic acid that causes necrosis (Venu et al., 2009).

Inadequate nitrogen in the plant appears to be an important factor in propagation of the pathogen as turfgrasses grown at low nitrogen fertility are more susceptible to the dollar spot pathogen infection (Allen et al., 2005). Under lower nitrogen fertility, there is a greater amount of senescent foliage compared with turfgrasses grown under higher nitrogen fertility, and senescent foliage acts as an energy source for the pathogen, increasing the spread of the fungus to disinfected plant tissues (Allen et al., 2005).

1.5 Symptomology of Dollar Spot

Symptoms of dollar spot vary with turfgrass species and management practices (Dernoeden, 2013). The chlorotic lesions first appear on individual leaves and when the disease progresses, lesions may become water soaked and ultimately tan or completely bleached in color (Smiley et al., 2005).

On golf course putting greens, lesions appear as small, circular, sunken, straw- colored patches that range in size from 5.0 to 7.5 cm in diameter (Walker, 2017; Walsh et al., 1999). During early spring, areas of initial infection in creeping bentgrass may have a reddish color (Dernoeden, 2013). A brown border surrounding the lesions frequently appears in an hourglass shape, being narrower in the middle than at the top (Allen et al., 2005). As disease becomes severe, necrotic patches combine together and form larger areas of straw-colored turf ranging from 6 to 12 cm in diameter (Couch, 1995). The pattern of patches shows tan bands across the leaf blade in closely mown turf at or below 1.25 cm (Beckley, 2018).

1.6 Management of Dollar Spot

1.6.1 Host Resistance

The research data regarding the susceptibility of turfgrass cultivars to dollar spot disease including creeping bentgrass is well documented (National Turfgrass Evaluation Program). Recent advances in turfgrass breeding have demonstrated that resistant cultivars of creeping bentgrass ‘Declaration’, ‘Barracuda’, ‘Luminary’, ‘13M’, ‘Landmark’ and ‘Memorial’ exhibited resistance to dollar spot disease (Skorulski, 2014). Murphy et al. (2016) showed that the cultivar ‘Declaration’ provided excellent disease control (< 3 infection centers m-2) among six resistant bentgrass cultivars, which resulted in three to five fungicide applications against dollar spot. In contrast, more (six to nine) fungicide applications were required for “Independence” for moderate disease control. It was concluded that cultivar was less important than timing of first application of fungicide to reduce number of applications needed (Murphy et al., 2016). In addition, although creeping bentgrass cultivars exhibit varying degrees of dollar spot susceptibility, utilizing a more resistant variety does not eliminate the disease but contributes to reduced onset of the disease, severity of the infection, and fungicide applications (Skorulski, 2014).

1.6.2 Chemical Control

The most common way to control pests on a golf course is the application of chemicals (Cropper, 2009). The first contact fungicides used to control dollar spot were cadmium and mercury-based products; however, as reported in the late 1960s by Cole et al. (1968), those chemicals failed to suppress the disease 20 years after this heavy metal-based fungicide was introduced (Ferstenmacher, 1980). These contact fungicides have become insensitive to dollar spot pathogen and they are no longer commercially available (Dernoeden, 2013). There are many fungicides labelled to control dollar spot disease including those classified as aromatic hydrocarbons, benzimidazoles, carboxamides, nitriles, Quinone outside inhibitors (QoIs), dicarboximides, demethylation inhibitors (DMIs), and phenylpyrroles (Latin, 2012). Benzimidazole type systemic fungicides labelled for dollar spot were released to replace heavy metal-based fungicides (Christians, 2011). Similarly, development of resistance to benzimidazole fungicides was reported as early as in the 1960s

(Cole et al., 1968; Massie et al., 1968). The persistent nature of disease that leads to repetitive use of fungicides through the growing season increased the resistance potential of populations of dollar spot pathogen to systemic fungicides (Latin, 2012). Systemic fungicides, including DMIs such as metconazole and propiconazole, dicarboximides such as iprodione and vinclozolin, strobilurins such as pyraclostrobin, benzimidazoles such as thiophanate-methyl, and succinate dehydrogenase inhibitors such as boscalid, became available for dollar spot control in 1970s (Latin, 2012; Warren et al., 1977). However, dollar spot resistance against the DMIs was also reported by several studies (Burpee, 1997; Golembiewski et al., 1995; Ok et al., 2011). The group of contact fungicides such as chlorothalonil is commonly used to control dollar spot on creeping bentgrass (Golembiewski et al. 1995; McDonald et al., 2006). The multi-site mode-of-action fungicide chlorothalonil is effective against many diseases, including dollar spot in creeping bentgrass (Shelton, 2017; Staff, 2014). Golembiewski et al. (1995) demonstrated that application of chlorothalonil at 10-day intervals inhibited dollar spot caused by a DMI-resistant strain effectively.

In addition, fluazinam, a multi-site preventative contact fungicide, has proven to be an effective dollar spot control product (Staff, 2014). Fluazinam has been demonstrated to have more than 98% control for severe dollar spot when applied at 14-day intervals (Agnew &Tredway, 2013). Another example of fluazinam’s ability to control dollar spot was shown in the trial where systemic fungicides such as boscalid (Emerald), propiconazole (Banner Maxx II) and 26GT (iprodione), and contact fungicides such as chlorothalonil 720, fluazinam (Secure) were applied. According to a study on the comparison of efficacy of fungicides, fluazinam (Secure) showed significantly better control than chlorothalonil 720 (chlorothalonil) and 26 GT (iprodione) (Agnew & Tredway, 2013).

The control of disease is achieved by not only using certain type of chemicals alone but also applying chemical combinations that could provide equal or superior control (Cropper, 2009). It is widely recommended that tank-mixing various chemicals of different modes of action to manage dollar spot decrease the potential for resistance development (Gilstrap, 2005). Fidanza et al. (2006) conducted a study by using tank mixes of fungicides with plant growth regulators such as paclobutrazol and

trinexapac-ethyl. The results indicated that the combination of chlorothalonil and plant growth regulators provided greater dollar spot control compared to the application with fungicides alone. Similarly, combining chlorothalonil with paclobutrazol and a wetting agent gave the best control compared to using fungicides alone (McDonald et al., 2006).

Christians (2011) points out that the best fungicide program involves using a strategy of alternating contact and systemic types of fungicides. Rotating fungicides with different modes of action contributes to delaying the possible selection of resistant biotypes of dollar spot (Dernoeden, 2013).

However, due to various environmental concerns, government-imposed restrictions have reduced the options of consistent controls that require high rate and application intervals of fungicides (McDonald et al., 2006; Staff, 2014). As well, public opposition to the use of synthetic chemicals continue to prompt more research on more efficient and eco-friendly disease control approaches and methods.

1.6.3 Cultural Control

The key to planning an effective disease management program for dollar spot in creeping bentgrass relies on integrating cultural practices into the program (Christians, 2011, p.302). Researchers have investigated the efficacy of several cultural practices in suppressing dollar spot (Couch & Bloom, 1960; Ellram et al., 2007; Nikolai et al., 2001). Turfgrass cultural practices aim to promote an environment which limits the activity of dollar spot pathogen (Allen et al., 2005). The cultural program chosen also impacts the effectiveness of fungicides (Christians, 2011). In this regard, cultural control is considered to provide proper conditions in disease management to limit the use of synthetic fungicides.

Most superintendents are finding a way to reduce fungicide use due to budgetary concerns and the risk of fungicide resistance (Throssell, 2017). In this sense, cultural control with integrated methods can be more effective and sustainable in order to maximize the potential for disease control practices (Allen et al., 2005). Several cultural practices have been investigated to reduce dollar spot on creeping bentgrass (Ellram et al., 2007). One of these practices is monitoring fertility and

applying nitrogen (N) since turfgrasses that are maintained under low nitrogen fertility are the most susceptible to dollar spot pathogen (Allen et al., 2005).

The key to controlling dollar spot through N fertilization is to implement a moderate, balanced program, because turfgrasses that receive either insufficient or excessive N can be more susceptible to dollar spot (Christians, 2011). In a 7-year study, Davis and Dernoeden (2002) evaluated nine N sources such as urea (46-0-0), sulfur coated urea (37-0-0), Milorganite (6-2-0), Sustane Medium (5-2-4), Earthgro 1881 Select (8-2-4); Earth Dehyrated Manure (2-2-2), Ringer Lawn Restore (10-2-6), Com-Pro (1-2-0; composted biosolids) and Scotts All Natural Turf Builder (11-2-4; poultry manure) on dollar spot severity. Both in 1998 and 2000, no significant differences were found among N sources in dollar spot severity, with the exception of Com-Pro which had highest infection centers. In contrast, Ringer Lawn Restore and sulfur coated urea treated plots had lower disease severity on most rating dates but there were no significant differences among other treatments in 1999. It was found that none of the organic N sources reduced dollar spot severity consistently compared to synthetic fertilizers. Research findings substantiated the view that N should be applied routinely at the time dollar spot was active in order for N to effectively reduce the disease (Dernoeden, 2013). The use of water-soluble N sources such as urea, ammonium nitrate, or ammonium sulfate was a good practice to manage dollar spot early in its development (Dernoeden, 2013).

Excessive moisture on the surface of the turf may also increase its susceptibility to diseases; thus, a balanced approach to irrigation is also crucial (Christians, 2011). Irrigation in the late afternoon or evening should be avoided to minimize leaf wetness duration (Allen et al., 2005). It is also recommended that morning dew on leaf surfaces be removed to lessen the inoculum source of dollar spot pathogen (Allen et al., 2005). In a study by Pigati et al. (2010), it was shown that morning mowing not only reduced the leaf wetness duration but also physically displaced dollar spot pathogen mycelia. Williams (1996) reported that removing dew through mowing and using a mower with reels disengaged reduced dollar spot severity up to 81%.

Ellram et al. (2007) demonstrated that the lowest dollar spot incidence was obtained when mowing daily at 0400h compared to mowing at 1000h and 2220h daily or on alternate days. In other words, the removal of dew at a time dividing the length of continuous leaf wetness into half was effective in controlling dollar spot. The impact of mowing frequency on dew removal that results in an increase in dollar spot severity may be due to a weakening of host defenses and altering plant growth habit (Putman, 2008).

Mowing practices and dew removal strategies combined with fungicide performance to control dollar spot disease in creeping bentgrass have also been evaluated. One study indicated that chlorothalonil generally provided effective control when applied in the morning after dew removal or at noon as opposed to morning applications to dew covered turf (McDonald et al., 2006). This may be due to the fact that chlorothalonil in the absence of dew might adhere to the dry foliage or might be less likely to become diluted. On the other hand, morning application of fungicides (chlorothalonil, propiconazole and iprodine) at the time of dew removal had no influence on dollar spot severity (Huang et al., 2015).

As another fundamental cultural practice, also light weight rolling has shown to have an effect on enhancing turf health and on reducing turf stress (Young, 2013). Rolling is a very old cultural practice, having been employed in turf management for more than a century. It was first introduced in the early 1900s on golf courses to increase ball roll speed and to improve surface uniformity (DiPaola & Hartwiger, 1994). As technology advanced, the cultural practice of turf rolling was revitalized with increased use of high sand root zones in the construction of putting areas (Young, 2013). The recommendation of United States Golf Association (USGA) minimized the detrimental residual compaction and improved the ball roll speed. (Beard, 1993). The demand for faster ball roll distance by golf course superintendents was increasing and their search for using rollers in a season-long program was limited (Nikolai et al., 2001). Subsequently, turfgrass researchers introduced the new generation of light-weight rollers to reduce pressure on putting greens (Young, 2013).

Rolling, which should be performed a maximum of three times per week and avoided when soils are wet, is best used to enhance ball roll distance in summer when mowing height is increased or when mowing frequency is decreased (Dernoeden, 2013). Hartwiger et al. (2001) showed the effects of rolling frequency and mowing height on both sand-based and native soil putting green rootzones. Rolling treatments were performed 0, 1, 4, or 7 times per week for a 10- week duration. Rolling rates of 4 and 7 times per week showed an increase in the bulk density; however, 4 and 7 times of rolling decreased turf grass quality (Hartwiger et al., 2001). Another study at Michigan State University investigated whether altering mowing height in combination with rolling practices may have an effect on residual ball roll distance in season-long programs (Nikolai et al., 1997). It was shown that rolling three times per week showed equal or faster than double cutting (5/32 inch) five times a week on the day of and the day after rolling treatments. (Nikolai et al., 1997).

In addition, rolling can also have a positive impact on reducing the disease severity of dollar spot. Nikolai (2002) showed that rolling three times per week reduced dollar spot and lessened the incidence of localized dry spot. The control mechanism of dollar spot suppression by rolling is still unknown; however, the speculated mechanism may include the removal of dew that interrupts the leaf wetness duration, the change in the physical properties or microbial community of thatch, or the stimulation of the plant’s defense response due to the slight stress created by rolling (Throssell, 2017; Giardona et al., 2012). In a three-year study conducted by Giordano et al. (2012) to determine the effect of various lightweight rolling strategies on dollar spot disease in creeping bentgrass in putting greens, rolling in the morning after mowing was shown to decrease disease severity of dollar spot consistently. Rolling treatment was reported to contribute to a favorable environment where colonization of bacterial populations on foliage and roots inhibited the growth of dollar spot pathogen on turfgrass (Giordano et al., 2012).

In addition, research findings indicate that timing is a prominent factor to reduce disease development rather than rolling frequency. Genova et al. (2016) conducted a study to assess the effects of time of day and frequency of lightweight

rolling on dollar spot disease incidence of creeping bentgrass fairway turf. It was reported that rolling in the morning significantly reduced dollar spot incidence compared to rolling in the afternoon. Another benefit of rolling is that it can be applied in conjunction with different fungicide programs to reduce the dollar spot and fungicide burden (Popko et al., 2015).

1.6.4 Biological Control

Biological control of plant pathogens can be achieved with the use of antagonistic microorganisms that either lower the population of disease pathogens or reduce their ability to cause injury to the turf (Kenna & Snow, 1999). In general, biological control strategies can be classified into two basic approaches: The first relies on the application of organic amendments to enhance naturally occurring populations of microorganisms in the soil. The second approach relies on the applications of specific bacteria and fungi known to suppress disease (Walsh et al., 1999). Both approaches stand as an attractive means of reducing fungicide applications to golf course turf since successful results have been obtained with mixtures of microorganisms as well as individual antagonists for controlling fungal turfgrass disease (Nelson & Craft, 1991b).

The first approach is defined as “general suppressiveness” which is an ability of soil to inhibit soil pathogens with antagonistic activity of soil microbiome (Weller et al., 2002). This function of soil encompasses multiple mechanisms including nutrient competition, antibiosis, hyperparasitism and/or induced systemic resistance (Weller et al., 2002). The concept of general suppression targets a variety of pathogens as opposed to specific suppression that can create conditions for soil fungistasis which is defined as the inhabitation restriction for the fungal propagules to germinate or grow in soil (Agtmaal, 2015). This is either caused by the presence of inhibitory compounds or via depleting carbon and nutrient sources from fungal propagules by the soil microbial community (Lockwood, 1977). Some volatile organic compounds might also be important as they enable competition between antagonists and plant pathogens in the rhizosphere (Effmert et al., 2012). In this complex environment where the plant-microbe associations are established in a competitive rootzone, the role of the microbes are strongly linked with physico-chemical soil components

(Agtmaal, 2015). The activity of the microbial community is influenced by the organic matter, pH, and clay content (Kuhn et al., 2009).

The approach of biological control as a means of management of plant disease is a broad concept which involves a range of control strategies. Addition of organic matter to soil is one of the potential disease management strategies that has been implemented for decades. Adding a large amount of biomass with animal manures, corn stalks and other plant materials enhances the suppressive capacity of beneficial indigenous microbial populations, which has usually related to general suppressive mechanisms (Bonilla et al., 2012). The increase in total microbial activity and microbial biomass creates a competitive environment for plant pathogens and is often correlated with disease suppressiveness (Janvier et al., 2007). In addition, the use of compost benefits plant growth and yield due to its effects on nutrient availability and improvement of physio-chemical characteristics of the soil, soil microbiota and microbial diversity (St. Martin & Ramsubhag, 2015). The effects of organic amendments on disease suppression through a shift in soil microbiota with those indicators are well known. However, it is noteworthy that the efficacy of suppression depends on the nature of the pathogen, the host and the environment that may differ in potential disease suppression (Bonilla et al., 2012)

The studies in the literature so far reveal that organic amendments, such as organic fertilizers, composts, and sludge, have provided suppression of diseases, including dollar spot, but with remarkable variation in their efficacy. As Kenna & Snow (1999) state, products including sewage sludge, brewery and manure composts, and natural organic fertilizers reduced dollar spot incidence in creeping bentgrass in field trials with highly variable results. Other research indicates that ammonium nitrate and sulfur coated urea provided an equal level of dollar spot management to some of these organic compounds (Nelson, 1992).

For those organic materials, it is important to know that disease suppressing composts are produced under ideal environmental conditions to allow for the colonization of both moderate and high temperature microflora. However, when applied, the nature of these colonizing microbial antagonists cannot be predicted, which means that their disease suppressive features might be unreliable (Kenna &

Snow, 1999). Thus, despite some documented research indicating up to 75 percent of control of turfgrass diseases, there is inevitably a substantial variation in their performance (Kenna and Snow, 1999, p.21). In one study conducted by Nelson and Craft (1992), the organic fertilizer Ringer Compost Plus (Ringer CP) and Ringer Greens Restore effectively suppressed dollar spot after one application. However, after the second application, propiconazole was more effective than the organic fertilizers. Conversely, Hoyland & Landschoot (1993) reported inadequate disease suppression with the application of Ringer CP. In another study, it was demonstrated that the organic fertilizers Ringer Commercial Greens Super, Ringer CP, Sustane, Milorganite, and Harmony did not reduce dollar spot severity significantly when compared with synthetic N sources (Landschoot & McNitt, 1997).

Concerning the mechanisms of action of these organic amendments, Liu et al. (1995) drew attention to the correlation between the ability of some organic amendments to suppress dollar spot and substantial increase in populations of soil microorganisms in turf.

On the other hand, preparations containing specific microbial antagonists to reduce severity of diseases have been reported to be slightly more successful and consistent (Kenna & Snow, 1999). With respect to dollar spot, however, the studies investigating the potential of bacteria and fungi for suppression have demonstrated varying degrees of success (Walsh et al., 1999). Nelson & Craft (1991) evaluated the effect of topdressings produced from corn-meal sand mixtures inoculated with Enterobacter cloacae (Jordan) Hormaeche and Edwards on creeping bentgrass infested with dollar spot pathogen. The application of isolate EcCT-501 was reported to suppress disease severity as effectively as that of propiconazole in the first year. They obtained up to 63% suppression of dollar spot on creeping bentgrass top- dressed with mixtures of sand-cornmeal infested with strains of the bacterium Enterobacter cloacae. Nevertheless, it was observed that the same isolate did not provide the same level of disease suppression in the following year. The authors attributed this ineffectiveness to the experiment area, the 60-year-old swards, which were believed to possess a diverse microflora that restricted the activity of Enterobacter cloacae.

There is also a biological fungicide (Bio-Trek 22G) registered in the United States containing Trichoderma harzanium which showed promise for control of dollar spot (Lo, et al., 1997). The spray applications of strain 1295-22 significantly reduced Pythium root rot, brown patch, and dollar spot of creeping bentgrass in turf in both greenhouse and field experiments (Lo et al., 1997). Bio-Trek 22G, a nontoxic and nonpolluting product, provided a proper establishment of T. harzanium in soil and on roots, thus leading to restoration of beneficial microbes in turf soils (Harman & Lo, 1996). Application of hypovirulent isolates of plant fungal pathogens has also been reported to be effective in suppression of dollar spot. Zhou & Boland (1998) demonstrated that hypovirulent isolate Sh12B reduced dollar spot as effectively as the fungicide chlorothalonil.

The commercially formulated biocontrol inoculants for turf diseases available in the United States include Trichoderma harzianum (Turf Shiled), Glioacladium catenulatem (Primastop), Pseudomonas aureofaciens (Spotless), Streptomyces lydicus (Actinovate), Bacillus subtilis (Companion), and Bacillus licheniformis (Ecoguard) (Nelson, 2003). Microbial inoculants have been studied and used in turfgrass management to control diseases (Nelson & Craft, 1999). For instance, P. aureofaciens TX-1 (Spotless) controlled dollar spot in addition to Anthracnose, Pythium root rot and blight, leaf spot, take-all patch, fairy ring, pink patch, gray leaf spot, Microdochium patch, summer patch and necrotic ring spot (Nelson, 1997). Similarly, the incidence of dollar spot on creeping bentgrass was reduced by using Fusarium heterosporum and other antagonists isolated from turfgrass foliage with the application of corn meal sand top dressing (Goodman & Burpee, 1991).

1.7 Organic Fertilizers and Soil Conditioners

Soil conditioners are materials added to soil to improve its physical properties (Weil & Brady, 2017) and to increase the performance of soils to enhance crop yields (De Boodt, 1990). Fertilizers, on the other hand, can be any organic or inorganic material supplement added to soil to improve its chemical condition which is essential to the growth of plants (Weil & Brady, 2017). Organic amendments, such as animal manures and composts, are any material of plant and animal origin that can be incorporated in soil for their ability to improve soil quality and plant health (Bonilla et

al., 2012). Some effects of soil quality on plant health have been related to soil suppressiveness against disease pathogens (Bailey & Lazarovits, 2003).

The common amendments and fertilizers used in turfgrass management are animal manures (poultry, cow and horse), municipal and industrial sewage sludges (biosolids or composted brewery sludge), and meals derived from plants or animals that are used as natural fertilizer (Nelson & Boehm, 2002). The first application of compost to turfgrass was by topdressing or mixing it into sand top dressings (Fitts, 1925). Topdressing is the practice of spreading a thin layer of sand or a blend of organic materials into the turf canopy to improve firmness, rootzone, smoothness and to control thatch (Christians et al., 2017; Lowe, 2015).The primary motivation for using natural fertilizers as the best source of organic matter is that they may influence the soil microbial activity by introducing the antagonism or manipulating the antagonistic organisms in the soil and on plant parts which help to suppress pathogen propagules (Liu et al., 1995). In general, organic nitrogen (N) applications are believed to reduce plant pathogens without causing a decrease in other microorganisms (Bailey & Lazarovits, 2003). The effects of numerous compost materials in soil-borne and foliar diseases have been documented by many researchers (Noble, 2011; Noble & Coventry, 2005). In a field study carried out by Lazarovits et al. (1999), the application of soy meal and meat and bone meal was reported to reduce the incidence of Verticillium wilt in potato.

Pan et al., (2017) reported that dollar spot disease reduction was achieved by the incorporation of mustard seed meal (MSM) both in the greenhouse and the field. However, the effect of MSM varied on incidence of dollar spot under field conditions. It was found that MSM reduced dollar spot incidence as effectively as the fungicide iprodione (Pan et al., 2017). Other studies showed that compost amendments reduce the severity and incidence of a wide variety of turfgrass diseases including dollar spot (Nelson & Boehm, 2002; Roulston, 2006).

Compost tea, microbially-enhanced compost extract, is another disease suppressive material that can benefit soil microbiology and turf growth (Shrestha et al., 2011). It is a solution of extracted beneficial microbes and nutrients obtained from compost (Ingham, 2005). It can be classified as aerated compost tea (ACT), not-

aerated compost tea (NCT) and anaerobic tea (Litterick, 2004). Compost teas have been shown to control a wide range of foliar and soil-borne diseases on agricultural crops such as corn, wheat, potato, cucumber and strawberry. (Kone et al., 2010; Litterick et al., 2004). Hsiang & Tian (2005) showed that compost tea-controlled dollar spot disease even though most of the compost teas resulted in significantly less suppression than chlorothalonil.

Disease occurrence in response to the application of compost materials may vary on different sites. The duration of suppression and degree of efficacy may be affected by compost composition, feedstock types, tea brewing process, rate, time, temperature, carbon and nutrient source for resident soil microorganisms (Hsiang & Tian, 2005; St. Martin, 2014). Kelloway (2012) indicated that mink compost tea has a positive effect on the suppression of dollar spot disease, which is attributed to the chemical components produced from anaerobic microorganisms. Compost tea is consistently effective at reducing dollar spot in in-vitro studies, but under field conditions, the effect of compost tea is much more variable and dependent on location (Kelloway, 2012). It was concluded that the control of turfgrass dollar spot with compost tea can potentially be used in an integrated management program; however, the results of dollar spot control were limited due to the inconsistent performance of compost amendments, which is related to lack of understanding of the disease suppression mechanisms in soil (Hsiang & Tian, 2007; Kelloway, 2012). The limited use of compost tea appears to be associated with complex dynamics of microbial ecological processes involved in the production and application of compost and compost tea (Kelloway, 2012). More research should aim to address these complexities and variations to improve the consistency and efficacy of disease suppression for particular compost types, pathogens, crops, soil and environmental conditions (Kelloway, 2012).

Research on enhancing soil suppressiveness against dollar spot disease on creeping bentgrass with organic fertilizer, and poultry and cow manures has provided promising outcomes. Nelson & Craft (1992) reported that selected composts prepared from turkey litter, sewage sludge and plant-animal by products consistently inhibited dollar spot disease. By contrast, there are also reports showing that natural

fertilizers are not more effective than synthetic N sources in reducing turfgrass diseases. Landschoot & McNitt (1997) tested seven natural organic fertilizers to compare their disease suppressive effects with synthetic N sources. The results showed that urea provided equal and better dollar spot control when compared to natural fertilizers. Similarly, Davis & Dernoeden (2002) evaluated the effect of nine natural fertilizers and composts on control of dollar spot disease. Urea, sulfur coated urea and poultry waste were the only N sources that suppressed dollar spot when disease pressure was in the low to moderate range. On the other hand, sewage sludge enhanced dollar spot disease and increased thatch. None of the N sources showed a reduction in dollar spot and no evidence of suppression and increased soil microbial activity was reported (Davis & Dernoeden, 2002).

Worm castings is the end-result of vermicomposting, the process in which organic material is excreted by earthworms after digestion (Lavelle, 1988). The source of vermicompost can be produced from various waste streams, such as animal manures, household wastes, and mixture of vegetable wastes (Adhikary, 2012). There is a slight difference between wormcastings and vermicompost materials. Worm castings are fully decomposed materials consisting of a combination of organic material and excrete of worms that are undigested whereas vermicompost is partially decomposed worm castings with organic materials. As organic matter passes through the earthworm’s gut, it is transformed into particles by enhancing the degradation of ingested material and the degraded organic matter comes out of the earthworms’ body in the form of casts (Dominguez et al., 2010). Vermicomposting is made in order to transform wastes and sludge into a safe and highly valued fertilizer and soil conditioner known as vermicast for use in agriculture, horticulture, nurseries, and recreation areas (Quintern & Morley, 2017).

Worm castings are considered superior to conventional composts for their ability to modify chemical, physical and biological properties of soil in a way to favour plant growth (Sharma et al., 2014). According to Edwards (1995), the microbial activity of beneficial microorganisms in castings is ten to twenty times higher than that of the microorganisms in the soil and other organic matter. It was reported that if solid vermicompost is turned into vermicompost tea, it can be easily used as a foliar

spray with the aim of promoting growth and suppressing the plant diseases (Arancon et al., 2008). A study showed that foliar application of vermicompost tea achieved a yield increase of 400 % in pecan nuts in the USA and eliminated pecan scab problem (Sinha et al., 2011). Compared to aerated compost, aerated vermicompost tea produced higher suppressive effect on Rhizoctonia solani, Fusarium oxysporum f. sp. and lycopersici, and weekly application tripled the dry weight of tomato plant (Morales-Cortes et al., 2018). Conforti et al. (2002) demonstrated the efficacy of aerated compost tea on turf grass growth and suppression of Microdochium nivale in a field trial at Presidio Golf Course.

In addition to disease suppression, the stimulating effect of worm casting on plant growth parameters has been reported for several plants including tomato, petunia, pine trees, potato, wheat, marigolds and sunflowers (Arancon et al., 2004, 2008; Atiyeh et al., 2000; Sinha et al., 2011; Zaller, 2007). Vermicompost contains auxins, cytokinin and the flowering hormone “gibberellin” secreted by earthworms which have an impact on fruit development (Adhikary, 2012).

Fish emulsion is the by-product of whole fish or fish waste that is heat and acid- processed. The soluble emulsion is derived by passing the liquid out of cooked fish (Abbasi et al., 2003). The product is then subjected to acidification with sulfuric acid for stabilization and inhibition of premature break down (Abbasi et al., 2003; Abbasi, 2011). It has been shown that fish emulsions are used as foliar fertilizers and pre-planting soil amendments. Some studies have extensively focused on the use of fish emulsion as a soil amendment in pathogen or pest suppression (Abbasi, 2010; Abbasi et al., 2006). Initially, it was shown that fish meal suppressed Verticillium wilt on tomato in naturally infested clay-loam soil more effectively than other organic amendments (Wilhelm, 1951). According to the findings of this study, none of the tomato seedlings amended with 1% fish meal showed wilt symptoms. Subsequent studies targeting other soil-borne diseases were conducted in growth rooms, greenhouses, micro plots, and fields to determine the suppressive effect of fish emulsion (Abbasi et al., 2006). Incorporation of 0.5% (mass/mass soil) fish emulsion into soil and peat-based substrate at 5 days before planting of radish provided more than 90% of control of cucumber damping-off disease caused by Rhizoctonia solani

and Pythium aphanidermatum (Abbasi et al., 2004). In contrast, fish emulsion (1, 2, 4%) did not show immediate protection against damping-off caused by Pythium ultimum on cucumber seedlings in infested peat mix; however, disease protection was achieved consistently when planting was delayed one week or more after adding fish emulsion in an infested muck soil (Abbasi et al., 2009). The effect of this amendment was also tested in artificially inoculated R. solani-infested sandy loam soil (Abbasi et al., 2004). 90% of radish seedlings showed effective control and they remained healthy when 0.5% (mass/mass soil) fish emulsion was incorporated 5 days prior to planting (Abbasi et al, 2004).

Abbasi et al. (2006) examined the effect of fish emulsion in two economically important soil borne diseases; Verticillium wilt and scab on potato. They mixed fish emulsion with soil at a rate of 0.5% and 1% in eggplant infected with V. wilt after inoculation in greenhouse and found that 1% of fish emulsion increased fresh and dry weight of plant biomasses. In the same study, however, the scab severity was not reduced on potato tubers when fish emulsion was incorporated at a rate of 0.5%. Fish emulsion was also tested as pre-planting soil amendment in micro plots. The trials amended with 1% showed significant scab reduction in seven soils (Abbasi et al., 2006). Their study was conducted in two commercial potato fields in Ontario from 2004 to 2005. In these field studies, 1% of fish emulsion reduced the scab and Verticillium wilt in both locations in 2004; however, tuber yield was affected by fish emulsion only in 2004 in one field (Abbasi et al., 2006). Their results indicated that the disease suppression by fish emulsion material was not soil-specific and fish emulsion was not effective in soil where the disease levels were high. These findings were comparable to the results of a previous study (Hoitink & Boehm, 1999) which demonstrated that disease suppression by fish emulsion on various diseases varied from batch-to-batch of the mix depending on the pathogen and microbial activity.

Other preliminary trials were conducted to test the impacts of fish emulsion as a foliar spray on bacterial spot of tomato and pepper caused by Xanthomonas vesicatoria of tomato and pepper. Weekly foliar sprays of neem oil and fish emulsion suppressed bacterial spot symptoms in both plants in a two-year study. Fish emulsion increased the total yield of tomatoes and pepper in some but not all years

(Abbasi et al., 2003). Furthermore, the growth promotion effects of fish emulsion were observed on tomato, tobacco, white Chinese leaf cabbage, radish and cucumber in the fish emulsion-amended peat-based mix and organic or muck soil in the absence of pathogens (Abbasi et al., 2004; Abbasi, 2011).

1.8 The Effect of Soil Quality and Health on Disease Suppression

The terms soil health and soil quality are used synonymously to refer to the functionality of soil systems and the same fundamental properties are taken into consideration when defining an enhanced soil ecosystem (Al-Kaisi & Lowery, 2017). Though various definitions have been proposed for soil health by scientists, the one made by Doran et al. (1999) has been cited the most widely: “Soil quality or health can be broadly defined as the capacity of a living soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health.” According to this definition, soil is a medium that supports the growth of plants, animals and humans, degrades dangerous compounds in the ecosystem, and provides nutrients for living things.

Soil health within a soil system is constantly changing as chemical, physical and biological characteristics do not remain stable as a result of human influence on soil health and changes in weather conditions (Al-Kaisi & Lowery, 2017). Relationships between soil microorganisms and their intimate associations with plants and animals strongly suggest that they are main contributors (Doran, 2002). Management and land use decisions greatly affect soil health, which requires the balance between soil functions for productivity, environmental quality, and plant health (Doran, 2002).

Attributes of soil quality can be classified as physical, chemical and biological functions of soil that are influenced by the type of soil management practices such as crop rotation, tillage, use of green manure, cover crops and external organic inputs (El-Ramady et al., 2014). Depending on these practices, the balance in soil organic matter can strongly differ, influencing the quantity, diversity and functions of soil microbiota as well (Bonilla et al., 2012). The soil

organic carbon pool, which is a key indicator of soil quality, has a strong relationship with soil fertility and agronomic productivity (Lal, 2015).

Relevant indicators of soil physical quality include aggregate stability, bulk density, soil organic matter, water transmission, aeration and gaseous exchange, effective rooting depth and soil heat capacity (Lal, 2015). Similarly, appropriate indicators of soil chemical quality include pH, cation exchange capacity, nutrient availability, and lack of any toxicity or deficiency. Relevant indicators of soil biological quality are soil organic matter, microbial biomass C, activity and diversity of soil fauna and flora and the presence/ absence of pathogens and pests (Lal, 2015). Soil enzymes are also considered good biological indicators of soil quality due to their rapid reaction to changes in soil management and their relation to soil microbial activities (Gregorich et al., 2005). Bandick & Dick (1999) reported that soil enzyme activities were higher in cultivated fields where cover crops or organic residues were added compared with control treatments without organic amendments.

The interaction of microorganisms in the rhizosphere is commonly related to changes in soil microbial communities and root exudates patterns (Mukesh & Varma, 2015). Being an important component of rhizosphere, microbial diversity along with soil properties plays an important role in soil health and crop productivity. These factors affect the plant growth, yield, plant protection, induced systemic resistance and soil quality (Mukesh & Varma, 2015).

The effect of soil amendments on soil biological systems has been researched considerably (Hatfield & Walthall, 2015). Agronomic practices such as the addition of organic amendments aim to improve the microbial biomass, diversity, community structure and physicochemical properties (Mukesh and Varma, 2015). In a study conducted by Badalucco et al. (2010), it was found that reduction in tillage and addition of manure to the soil increased soil microbial biomass and soil organic matter content. Iovieno et al. (2009) also showed that compost materials significantly increased microbial activities when coupled with reduced tillage. They pointed out that changes in soil microbial activity and soil organic carbon (SOC) were cumulative, which demonstrated the effect of repeated compost applications. Many studies show that increase in soil organic matter through addition of manure, compost, and organic

fertilizer combinations is necessary for nutrient cycling and soil aggregation (Hatfield & Walthall, 2015).

The improvement of soil quality and fertility through organic amendments has been shown to develop the soil’s capacity for suppression of soil-borne pathogens (Bailey & Lazarovits, 2003). This suppression is believed to be promoted by competition with the pathogen for resources or through direct antagonism (Bonilla et al., 2012). It is well evident that the use of organic amendments like cover crops, animal and green manure, composts peats, and plant residues can be a successful disease control strategy.

A comprehensive study found that there is a correlation between some physiochemical properties of soil and disease suppressive capacity (Janvier et al., 2007). One of the parameters most analyzed was N content of soil. A positive association was found between the N content of soil and the suppressive impact of Pseudomonas syringae on bean and cucumber (Rotenberg et al., 2005), and Gaeumanomyces graminis var tritici (Ggt) and R. solani on wheat (Pankhurst et al., 2005). Tenuta & Lazarovits (2004) demonstrated the effect of nitrogenous organic amendment on microsclerotia of V. dahliae in several soils. They found that NH3 and

HNO2 were able to suppress microsclerotia of V. dahliae. Similarly, a higher C level resulted in a lower incidence of Fusarium culmorum on barley (Rasmussen et al., 2002), and Pythium damping-off of tomato (van Bruggen & Semenov, 1999). However, increased ammonium: nitrate resulted in increased the Fusarium wilt severity (Borrero et al., 2012; Oyarzun et al., 1998).

Li et al. (2017) investigated the effects of NPK chemical fertilizer and bio- fertilizers containing bacteria (B.subtilus HJ5 and B.subtilus DF14) on soil physicochemical properties, biological activities, antagonistic bacteria and cotton V. dahliae. Compared with NPK fertilizer, 60% chemical + 40% bio-fertilizer treatment significantly increased soil chemical properties of total nitrogen, available phosphorus, available potassium, soil organic carbon and dissolved organic carbon. Bio-fertilizers also strengthened the enzyme activities of the microbial populations and antagonistic bacterial abundance, leading to suppression of pathogens (Li et al., 2017).

Larkin et al. (2011b) reported that soil improvement did not result in reduction of soil-borne diseases although it generally contributed favorable results. This can be explained by the type, age, and maturity of the compost used as these characteristics of amendments could have distinctive effects on disease suppression (Larkin et al., 2011b). Research directed at understanding the mechanisms of organic matter in soil to achieve the desired disease suppression will fill a gap in this field of study. As a result, maintaining the abundance and diversity of beneficial soil microbial communities can be achieved through improvement of soil quality. Accordingly, a deeper understanding of the effects of an adopted disease management method on soil quality and health may help to obtain desired results in disease suppression.

1.9 Project Rationale

Dollar spot disease caused by dollar spot pathogen is a major concern for superintendents since it occurs on most types of turfgrasses in highly managed golf greens and fairways. Dollar spot known to reduce the lawn’s aesthetic quality and leads to an overall decline in turf strength. The disease is highly destructive on creeping bentgrass in the northern United States and Canada. Dollar spot most often occurs through July and August, but if the weather conditions are conducive to the disease, it can persist from June until October in Ontario. The symptoms of dollar spot exhibit on leaf blades straw-colored centers and red-brown margins. Complete control of dollar spot is difficult and costly as it puts an excessive burden on golf courses to spend tens of thousands of dollars to apply multiple fungicides. Repeated fungicide applications also result in development of fungicide resistance and raise public concerns about economic and environmental issues. In this respect, there has been a shift from chemical towards alternative management practices to reduce the need for fungicide applications. Early studies showed that cultural practices such as mowing, irrigation and rolling reduced the level of dollar spot severity to an acceptable level. In addition, the biological control of dollar spot has been the subject matter of a considerable amount of research. Numerous studies aimed to assess if occurrence of dollar spot could be reduced by manipulating the soil ecology through the addition of organic matter to create suppressive soils, leading to inhibition of the causal fungi. The addition of numerous nitrogen sources, soil conditioners, and organic fertilizers play an important role in increasing organic matter. Soil

conditioners remain to be used for managing dollar spot disease and enhancing the soil quality. Natural fertilizers, such as activated sewage sludge and fertilizers composed of plant and animal meals have also been reported to be highly suppressive to dollar spot disease. Even though organic amendments have been shown to have the potential to reduce the incidence and severity of dollar spot and stimulate plant growth, some concerns exist over turfgrass responses following the application of such amendments. Thus, due to their significant role in minimizing fungicide usage, more research should focus on understanding their effects on chemical and biological soil properties and soil microbial activity.

There is a need for more eco- friendly turf products to provide long-season control of dollar spot. The findings about the effects of soil conditioners such as worm castings, fish emulsion, and fish hydrolysate on dollar spot disease are very limited in previous research. There is also little to no previous research on the implementation of an integrated approach to determine the effectiveness of soil conditioners applied in conjunction with cultural treatments such as rolling, and chemical treatments to reduce the dollar spot severity. In addition, as soil conditioners have shown promise for development of soil microbial populations and thus soil health, any attempt to develop management practices providing long-term soil health improvement by reducing the use of fungicides will be of great value to achieve sustainable disease management. To achieve more environmentally friendly disease management, proper cultural practices and a number of organic amendments should be adopted as such an approach will also contribute to maintaining plant and soil health while aiming to ward off dollar spot.

The effects of fish emulsion, worm castings and spent mushroom compost on multiple diseases have been studied in the past; however, to the best of our knowledge, no previous study has investigated these specific soil conditioners, especially in combination with each other, for their effects on the suppression of dollar spot disease. The research presented in this thesis evaluated the effects of various non-fungicide treatments alone or in combination, on dollar spot development, under field conditions and in a controlled environment. The purpose of this research is to investigate the viability of alternative management strategies for

dollar spot that rely on the use of soil conditioners with the aim of minimizing fungicide use.

1.10 Research Hypothesis and Objectives

This research was designed to test the hypothesis that soil conditioners will reduce dollar spot severity by increasing microbial activity and antagonism and promoting soil and turf grass health.

The present study has the following greenhouse and field trial objectives:

Greenhouse trial objectives were;

1- To determine whether soil conditioners reduce dollar spot severity on creeping bentgrass turf

2- To determine whether soil conditioners enhance turf color

Field trial objectives were;

1- To determine the ability of soil conditioners and rolling practices to reduce dollar spot severity and to enhance turf color

2- To determine the effects of soil conditioners and rolling practices on soil microbial activity in terms of reducing dollar spot severity

2 Materials and Methods

2.1 Greenhouse Studies

The greenhouse study was performed conducted twice at different times and both studies were conducted at the greenhouse of University of Guelph in the Edmund C. Bovey Building, ON, Canada in 2019. The first greenhouse study began on 31 January and second greenhouse was initiated on 21 May.

2.1.1 Preparation and Growth Conditions of Plants Materials

Seeds of creeping bentgrass cultivar ‘Penn A-4’ were used in this experiment due to its high susceptibility to dollar spot disease (Honig et al, 2003). Polyvinyl chloride (PVC) tubes were used at a length of 40.5 cm with 8 cm inside diameter (i.d.). Prior to seeding, the bottom 10 cm of the tubes were filled with pea gravel and the top 30 cm were filled with the top edge 100% siliceous sand. ‘Penn A-4’ was seeded on the surface of the tubes at a rate of 5g/m2 (Figure 2.1 A&B). Following seeding, the surface sand was lightly rolled out to ensure uniformity (Figure 2.1 D). Tubes were placed under automatic misters and were misted for 45-second intervals every 30 to 60 minutes, depending on sunlight and humidity in the greenhouse until seeds had germinated and emerged. In addition, to prevent the surface and seeds from drying out, seeds were manually misted for an additional 15 seconds every hour with DI water. Five days after seeding, Microprilled urea was applied (46N-0P-0K) to all of the pots and followed by misting with 130 mL water for 30 s to allow fertilizer to infiltrate the rootzone. Pots were lightly top-dressed with the siliceous sand to remove any surface imperfections caused by the fertilizer application (Figure 1.1 C). Fifty mL of urea solution was applied to each pot twice every week at a rate of 0.1 mg N / cm2, equivalent to 0.1 kg N / 100 m2 until the creeping bentgrass was established (Watson, 2009). A plastic collar was placed on the rim of the PVC tube to maintain turf at fairway height (6 mm) and the turf was cut using sharp manual grass shears two mornings per week (Mondays and Fridays). The clippings were removed after mowing using a brush, although this led to a small percentage of clippings being left behind. Once the creeping bentgrass was established, pots were fertilized with 20 mL of tank-mixed liquid fertilizer (20N-8P-20K) at a rate of 0.1 mg N / cm-2, equivalent

to 0.1 kg N / 100 m2 from March 20 to April 17. To hasten the fill-in, pots received 20- 8-20 fertilizer twice a week, from April 22 to May 9.

Pots were watered 3 times per day during the study with approximately 400 mL of water to prevent from drought stress.

A B

C D

2.1.2 Experimental Design

Both greenhouse experiments were arranged in a Complete Randomized Design (CRD). The first study included nine treatments replicated five times. The nine treatments included: Fish emulsion (FE) (Alaska Fish Fertilizer, 5-1-1, Toronto Hemp Company, ON), Fish hydrolysate (FH) (2-3-1 General Hydroponics G5352 Biomarine Enzymatically Digested Fish Protein, Toronto Hemp Company, ON), Aerated Worm Castings Tea (AWCT) +urea, Worm castings (WC) (Gai Green Organic Worm Castings, Toronto Hemp Company, ON), Spent mushroom compost (SMC) (1-0.1-1 Premier Mushroom Compost, Home Depot, ON ), FE+WC, AWCT+urea+FH, urea (46-0-0) as a negative control, and chlorothalonil (Daconil 2787 Flowable) + urea as a positive control. The second study included ten treatments replicated five times. An additional treatment, urea (half rate) at a rate of 0.5 kg N / 100 m2 was included in second greenhouse study. Other treatments remained the same as in the first greenhouse study.

Figure 2.2: Brewing Aerated Worm Casting Tea

2.1.3 Preparation and Application of Soil Conditioners

SMC and AWCT+urea required preparation prior to application whereas FE, WC and FH did not require any preparation.

2.1.3.1 Soil Conditioner Preparation

Prior to application, SMC was put into trays and allowed to air dry for 1 week in the laboratory. SMC was crushed by hand to break up compaction and then

passed through a 0.125 mm mesh sieve (Aamlid and Landschoot, 2007). To prepare tea from the castings, a 2L beaker was filled with 500 mL of DI water and was supplemented with 1.58 mL of unsulphured molasses. The molasses was blended with DI water until dissolved and then 45 g of worm castings was distributed over the beaker. A hose was placed into beaker to act as an air bubbler to ensure circulated water with constant aeration for 24 hours (Figure 2.2). Before each application, worm castings tea was brewed 1 d before the application and used immediately. The preparation process of aerated worm castings tea was identical for both greenhouse studies.

The chemical and physical properties of soil conditioners were analyzed by A&L Canada Laboratories East Inc., London, ON, Canada. The results of the analyses are shown in Table 2.1.

2.1.3.2 Soil Conditioner Application

Creeping bentgrass was cut at 6mm fairway height before being subjected to soil conditioner applications. All liquid soil conditioners were put into 50 mL falcon tubes, mixed with 20 mL of DI water and applied evenly on every pot (Watson, 2009). SMC and WC were sprinkled and then pots were watered with 20 mL deionized water. As each soil conditioner contains a different amount of N, the product application rate had to be adjusted to ensure each tube received the same amount of total nitrogen (Table 2.1). An additional treatment, urea (half rate) at a rate of 0.5 kg N / 100 m2 was included in the second greenhouse study. Soil conditioners were applied at a rate of 0.071 kg N / 100 m2 weekly which is equivalent to recommended season long N rate at 1.7 kg /100m2

After the initial application of treatments, the sample of compost tea was taken to A&L Canada Laboratories East Inc., (London, ON, Canada) for its chemical composition. Based on N-P-K results analyses shown in Table 2.1, AWCT had zero N and therefore we supplemented our single AWCT regime with 46-0-0 urea (seasonal rate at 1.7 kg/100m2) for the subsequent applications. Fertility treatments were applied every 2 weeks over a 14-week period. For the first greenhouse study, the soil conditioner applications commenced on 14 May when the turf cover in the

pots was at 100 percent. Soil conditioner applications in second greenhouse study were made as described above. For the second greenhouse study, the soil conditioner applications commenced on 12 August when the turf cover in the pots was at 100 %.

Table 2.1: Chemical and physical analyses of fertilizer treatments

Soil conditioners

Spent Mushroom Lab analyses Worm Castings Fish Hydrolysate Fish Emulsion Compost

Nitrogen (insoluble)% 2.03 2.67 3.99 N/Az

Nitrogen (Total) % 2.10 2.89 7.41 10.25

Phosphorus (Available)% 0.5 BDLy 9.1 5.7

Potassium (Soluble)% 0.3 0.1 3.6 3.0

Total organic matter % 64.56 72.25 75.98 71.39

C:N ratio 16:1 13:1 13:1 3:1

Moisture % 73.27 60:87 60.87 48.40

z N/A= Not applicable y BDL= Below detectable level

Table 2.2: Application rates for soil conditioner treatments in the first and second greenhouse study for 14-week period, 2019

Product required to Experiment long target Target N rate kg/ 100m2 Product (Treatments) z N-P-K achieve desired rate for N rate (kg/ 100 m2) (weekly) season (kg/ m2)

SMC 2.10-0.5-0.3 1.0 47.6 0.071

WC 2.89-0-0.1 1.0 34.6 0.071

FH 7.41-9.1-3.6 1.0 13.4 0.071

FE 10.25-5.7-3.0 1.0 9.7 0.071

y 50 % FE+ 50 %WC 10.25-5.7-3.0 + 2.89-0-0.1 1.0 22.1 0.071

x AWCT+urea 0-0-0.1 + 46-0-0 1.0 34.6 0.071

50 % AWCT+urea+ % 50 FH 0-0-0.1 + 46-0-0 + 7.41-9.1-3.6 1.0 7.83 0.071

urea 46-0-0 1.0 2.1 0.071

w urea (half rate) 46-0-0 0.5 1.08 0.035 z SMC= Spent Mushroom Compost, WC= Worm Castings, FH= Fish Hydrolysate, FE= Fish Emulsion, AWCT+urea= Aerated Worm Castings Tea, AWCT+urea+FH= Aerated Worm Castings Tea + urea + Fish Hydrolysate y Each treatment combination consists of half rate of season long target N. x The treatment of AWCT+urea point to one single treatment. w urea (half rate) was added as an additional treatment in second greenhouse study. The first greenhouse study consisted of nine treatments while the second study consisted of ten treatments.

2.1.4 Fungicide Application

For the first greenhouse study, the first fungicide treatment was applied on 24 June, one day prior to inoculation. The pots were treated with chlorothalonil (Daconil 2787 Flowable, Sygenta Crop Protection, Canada), containing 40% of active ingredient (a.i). Each pot received 0.005 mL a.i., which is equivalent to 100 mL /100m2 as a preventative control for dollar spot. Pots were sprayed every 14 days and always on the day before fertilizer applications with hand sprayer to coat all foliage tissue. For the second greenhouse study, the fungicide application was made on 22 September in 2019. The same procedure as in the first greenhouse study was followed.

2.1.5 Pathogen Inoculum Preparation

For both greenhouse studies, a local isolate of C. jacksonii that had been stored since 2018 was obtained from the Guelph Turfgrass Institution (GTI) and maintained on potato dextrose agar (PDA) at 4˚C.The pathogen was sub-cultured and grown on PDA for a period of 5 d at 22˚C until the fungal colony fully covered the edge of agar plates. Four hundred grams of Kentucky bluegrass (Poa pratensis) (Ontario Seed Company, ON, Canada), used as a medium to grow fungi, was soaked in deionized water for 24 h. Water was discarded through a metal strainer and seeds were rinsed with water. The seeds were split into 200 g portions and each was placed into a 2L beaker and covered tightly with heavy aluminum foil. Beakers were autoclaved for 45 min at 121˚C three times with a 24-hour period between each cycle. Once the beakers cooled down, the seeds were inoculated with C. jacksonii under aseptic conditions. The media was cut into small cubes (1 cm x 1 cm) using a sterilized scalpel and scraped into autoclaved seed beakers. Three plates of fungal cultures were used for each beaker. With the help of a scoopula, seeds were stirred thoroughly to ensure even distribution of cultures. Beakers were again covered with aluminum foil and incubated at 20˚C for 3-4 days. Once the mycelia was visible (usually within 3 d), seeds were laid out in a laminar flow hood to dry on sterilized trays for 48 ho (Figure 2.3). After fluffy white mycelia colonized the seeds, they were placed in paper bags, weighed, labeled and stored immediately at -20˚C until needed.

Figure 2.3: Drying Kentucky Bluegrass seed inoculated with C. jacksonii in a laminar flow hood for 48 h

2.1.6 Inoculation Protocol

The frozen Kentucky bluegrass (Poa pratensis L.) seeds infested with C. jacksonii were placed in a small container and weighed before being put into paper bags. Prior to inoculation of the turf, water was sprayed on the grass with a hand sprayer until the leaves were completely wet. Five g/m2 of infested seed was applied uniformly to each pot using a scoopula (Figure 2.4& Figure 2.5). The pots misted with water and plastic resealable bags were placed on the pots to provide leaf surface wetness and uniform humidity for the development of dollar spot (Figure 2.6). The inoculation dates for the first and second greenhouse studies were 25 June and 23 September, respectively.

Figure 2.4: Sprinkling seed inoculum on the surface of the pot using scoopula

Figure 2.5: C. jacksonii infested seeds on the surface of the pots

Figure 2.6: PVC tubes covered with the resealable bags

2.1.7 Data Collection

For the both greenhouse studies, turf color data was assessed bi-weekly during the trial period from 25 June to 21 August. For the second greenhouse study, turf color data were collected from 23 September to 18 November. Turf color ratings for both greenhouse studies were taken every 14 days based on the NTEP (National Turfgrass Evaluation Program) scale of 1-9, where 9 represented the darkest green color, 6=minimum acceptable color, and 1= completely straw-brown color turf. The pots were rated for disease severity when the first symptoms occurred (Figure 2.7). The data collection for the disease severity assessment was started 1-week after inoculation.

Disease severity was visually rated every week on the basis of percent of the pot area exhibiting symptoms with 0= no disease and 100= 100% (Boulter et al. 2002). To examine the effects of soil conditioners on plant biomass, clippings were harvested one week after the last soil conditioner application. Grass was cut and collected for clippings in an aluminum tray to prevent any loss during mowing After being cut, clippings were placed in mini-manila envelopes and oven dried at 60˚C for

48 h and then subsequently weighed to determine fresh and dry weight. The area under disease progress curve (AUDPC) was calculated for each treatment using disease severity ratings from July 3rd through August 6th for GH study 1 and from September 30th through November 11th for GH study 2 using the equation: AUDPC

= Σni-1=1 ([yi + y (i + 1)] / 2) (ti+1) - ti), where yi is the disease severity at the ith rating date, ti is the day of the ith rating and n is the total number of evaluation (Campbell and Madden, 1990).

To collect root biomass, first the verdure (consisting of shoots and stolons) was separated from the roots using a knife. Next, the entire root zone column was removed from the PVC tube. Finally, the soil column was sectioned into three depths: 0-5, 5-10 and 10+ cm. Each root section was washed gently by hand over a 2 mm sieve/ pan under running tap water to prevent any root loss until most the sand particles were washed away and the roots were fully cleaned. Roots were transferred into a water filled bowl and washed again to eliminate the remaining sand particles. After the washing procedure, fresh weights of roots were recorded, and each sample was put in a mini-manila envelope and sealed. The envelopes containing the roots were oven dried at 60˚C for 5 d. To get more consistent root biomass measurements, dry roots were then ashed in a muffle furnace at 500˚C until the organic matter was burned off and the resulted ash weight was subtracted from the dry weight in order to obtain ash-free dry weight. For the second greenhouse study, the same procedure was again followed in order to collect data for clippings, AUDPC, and root biomass.

Figure 2.7: The first visible white cottony mycelium on the leaf blades of creeping bentgrass, one week after inoculation

2.1.8 Statistical Analyses

All statistical analyses were performed using SAS, University Edition, Version 9.4, Cary, NC, using Proc Glimmix (Generalized Linear Mixed Model). The data set was analyzed using repeated measures to determine the time-by-treatment interactions for disease severity, turf color and root biomass. The “autoregressive (ar1)” option covariance structure was selected for repeated effects. Treatment means were compared using the Tukey-Kramer adjusted least squares means (lsmeans). Differences were significant at p< 0.05 and were identified using the LINES option in the LSMEANS statement in SAS. The disease severity of the first greenhouse study and root mass data were derived under the assumption of a log normal distribution as the data were not normally distributed. The “dist=lognormal” option was generated for the distribution of severity and root biomass data due to the violation of the assumption of normality. The root and severity data of lsmean estimates were back transformed from the log scale format for variables to be interpretable. Correlation analyses was performed to determine the relationship between tissue N content and AUDPC of dollar spot and also tissue N content and clipping yields.

2.2 Field Studies

2.2.1 Site Descriptions

The field study was conducted at two different locations constructed to USGA specifications at Guelph Research Station, University of Guelph, Guelph, ON, Canada in June 2019. The first site was located in the original Guelph Research Station (GRS 1) (328 Victoria Rd S, Guelph) on the established-on ‘Penn A-4’ cultivar of creeping bentgrass putting green. The site plots were maintained under typical golf course putting green conditions and mowed 5 times a week at a height of 3 mm. The second site was located at the newly constructed Guelph Research Station (GRS 2) (College Ave East, Guelph, ON) on a creeping bentgrass putting green established with cultivar ‘007’. The putting green area was USGA specification 80:20 (sand: peat) putting green. The experiment was set up as a split plot randomized complete block design (RCBD) with 4 replications that included a 2x9 factorial design at both locations. The whole plot (13 m long x 9.6 m wide) treatment was rolling (rolled vs. unrolled), while the nine subplot treatments were the soil conditioner treatments; FE, FH, SMC, WC, AWCT+urea, AWCT+urea+FH, FE+WC, chlorothalonil and urea (control) in each strip measuring 1.2 m x1.5 m were randomized within whole plot. There were 18 experimental units within each block.

2.2.2 Preparation and Application of Soil Conditioners

2.2.2.1 Soil Conditioner Preparation

SMC was put into trays and allowed to air dry for 1 w in the laboratory before application. SMC was crushed by hand to reduce aggregate and particle size, then was passed a 0.125 mm mesh sieve (Aamlid and Landschoot, 2007). Aerated compost tea was prepared as described in greenhouse section 2.1.3.1. All plots received the first soil conditioner application in both locations on 11 June 2019. The soil conditioner treatments were applied in 14 d intervals over a 14 w period. (June, July, August, September). As each soil conditioner contains a different amount of N, the product application rate had to be adjusted to ensure each tube received the same amount of total nitrogen same amount. Soil conditioners were applied at a rate of 0.107 kg N / 100 m2 weekly which is equivalent to recommended season long N rate at 2.5 kg /100m2 (Table 2.3).

2.2.2.2 Soil Conditioner Application

The sprayer volume was adjusted to recommended application cover volume commonly used in typical golf courses (8 L / 100 m2). All liquid soil conditioners were mixed in a 2 L of plastic bottle and then applied to plots using a compressed air- powered, 4-flat fat nozzle bicycle sprayer (8 Tee-Jet 8001 VS) calibrated to deliver 150 mL /m2 at a pressure of 137 kPa, equivalent to sprayer volume of 15 L/100m2. The two solid soil conditioners SMC and WC were sprinkled across the plots as evenly as possible and then brushed over the entire study area. AWCT was filtered using a 2 mm sieve to separate the solid from the liquid before application and was then applied using a hand sprayer to provide uniform coverage to the plots. As the spray nozzles had a narrow width and did not cover the edges of plot, the evaluated plot area was considered to have a size of 1x1.5 m and the subsequent application rates were altered accordingly. Throughout the study, the trial area was irrigated to prevent drought stress.

Table 2.3: Application rates of soil conditioner treatments in field studies, 2019

Product required to Experiment long target Target N rate kg/ Product (Treatments)z achieve desired rate N-P-K N rate (kg/ 100 m2) 100m2 (weekly) for season (kg/ m2) SMC 2.10-0.5-0.3 1.5 71.4 0.107

WC 2.89-0-0.1 1.5 51.9 0.107

FH 7.41-9.1-3.6 1.5 20.2 0.107

FE 10.25-5.7-3.0 1.5 14.6 0.107

y 50 % FE+ 50 %WC 10.25-5.7-3.0 + 2.89-0-0.1 1.5 38.2 0.107

x AWCT+urea 0-0-0.1 + 46-0-0 1.5 3.2 0.107

50 % AWCT+urea+ % 50 FH 0-0-0.1 + 46-0-0 + 7.41-9.1-3.6 1.5 11.7 0.107

urea 46-0-0 1.5 3.2 0.107

chlorothalonil+urea 46-0-0 1.5 3.2 0.107 z SMC= Spent Mushroom Compost, WC= Worm Castings, FH= Fish Hydrolysate, FE= Fish Emulsion, AWCT+urea= Aerated Worm Castings Tea, AWCT+urea+FH= Aerated Worm Castings Tea + Fish Hydrolysate y Each treatment combination consists of half rate of season long target N x The treatment of AWCT+urea point to one single treatment.

2.2.2.3 Fungicide Application

The first fungicide application in both locations began on 23 July 2019. The plots were treated with the fungicide chlorothalonil (Daconil 8727 Flowable, Syngenta Crop Protection, Canada), containing 40% of a.i. Chlorothalonil was applied at a rate of 1.5 mL a.i. per plot which is equivalent to 100 mL / 100 m2. Each fungicide subplot was sprayed as a preventative basis at 10-14 days interval before fertilizer treatments with a 4-nozzle compressed air sprayer equipped with Teejet 8001VS flat fan nozzles at 137 kPa.

2.2.2.4 Inoculum Preparation and Application

The inoculum was prepared as described in the Greenhouse trial. Plots were inoculated on July 24, 2019 for both sites. Inoculum, which was put into individual mini-manila envelope in 9 g portions for application to 1.8 m2 plots, was spread by hand as evenly as possible across each plot with 5 g/m-2 Kentucky bluegrass seed inoculated with the C. jacksonii isolate. Plots were irrigated to prevent from drought stress.

2.2.2.5 Rolling Application

The rolling treatments for both locations (GRS 1 and GRS 2) were conducted from August 8 to September 14, 2019. The Old site was rolled using Greens Iron 3900 (24.8 kPa) while New site was rolled by ToroGreenspro 1260 roller (26 kPa). The sites were rolled three times a week early in the morning, including Monday, Wednesday and Friday. Putting greens were mowed five times a week at 3 mm without clippings removed.

2.2.2.6 Soil Microbial Respiration Measurement

Soil samples were collected (0-10 cm depth) from both locations on the same day. Four soil cores were removed randomly from each plot. Before they were put in resealable bags, foliage and thatch layer were removed immediately. At the end of the collection of soil samples, the putting green was top dressed with sand to fill the sample collection holes. All soils were taken to laboratory and put into trays and air dried at room temperature. Microbial respiration was measured using a Solvita Soil

Respiration Test Kit (A&L Canada Laboratories Inc., London, ON). To measure CO2

burst, first, air-dried soil samples were passed through a 2mm sieve, then 40 g was and placed into a plastic beaker and gently tapped to allow soil to become level. Twelve mL of DI water was dribbled slowly using a pipette onto the soil surface and then the small plastic beakers were placed in glass jars. Color CO2 probes were put alongside the plastic beaker. All the glass jars were closed tightly and incubated in the dark at 20˚C room temperature. After 24 hours, jars were opened, and the color

CO2 probes were inserted into a digital color reader (DCR). The CO2 respiration was measured according to two values: the color number based on measured optical density of the test gel and Co2-C ppm.

2.2.2.7 Soil Organic Matter (SOM) Measurement

Five cores of soil samples were taken randomly from each plot to a depth of 0- 10 cm to determine organic matter content from each location. Thatch layer was removed before it was put into resealable bags. All soil samples were air dried in trays for 1 week. The SOM was measured using the Loss on Ignition (LOI) method proposed by Robertson (2011) with some modifications. First crucibles were weighed and 5 g of soil from each plot was placed in crucibles and weighed. Next, crucibles were heated at 100˚C overnight in a drying oven. Then, crucibles were immediately placed in a desiccator (Bel-Art™ SP Scienceware™ Space-Saver Desiccators) to prevent wetting the soil from atmospheric humidity. The soil samples were weighed again and recorded as a pre-ignition weight. Next, all samples were transferred in a muffle furnace (650, Model 58) and heated to 500˚C for at least 16 h. When the muffle furnace cooled down, samples were immediately put in desiccator. Soil mass of 500˚C after combustion was weighed and recorded as post-ignition weight. The percentage of OM was calculated using the following formula:

푝푟푒−𝑖𝑔푛푎푡𝑖표푛 푤푒𝑖𝑔ℎ푡(𝑔)−푝표푠푡 𝑖𝑔푛푎푡𝑖표푛(𝑔) % OM = 푥100 푝푟푒−𝑖𝑔푛푎푡𝑖표푛 푤푒𝑖𝑔ℎ푡(𝑔)

2.2.2.8 Soil Aggregate Stability

The aggregate stability was measured according to Wet Sieving Apparatus proposed by (Eijkelkamp Soil& Water, 2018). Four g of 1-2 mm air-dried aggregates using a screen with mesh opening 0.25 mm were placed on the sieve apparatus. Aggregates were pre-moistened with deionized water using plant sprayer for 5-10

minutes. Next, deionized water was put into cans to cover the soil and the cans were placed into sieve holders which, then, were immersed in deionized water to oscillate for 3 minutes. After the water was removed, these cans were filled with dispersing solution (containing 2 g/L sodium hexametaphosphate/L for soils with pH > 7 and was continued sieving until the sand particles left on the sieves. The cans containing materials from aggregates were placed in oven and dried at 110˚C until the water was evaporated. After drying, aggregates were dried in small aluminum trays were weighted and recorded as a final weight. The percentage of aggregate stability was calculated using the following equation:

푾퐟퐰−ퟎ.ퟐ 푾푺푨 x 100 = 푾흄 where WSA= index of water-soluble aggregate; Wfw= is the final weight of aggregates; 푾흄= initial weight of aggregates placed on the sieve prior to wetting; Wfw = ( 푾흄- 푾풅풘); 푾풅풘= weight of aggregate after oven dried at 110˚C

2.2.2.9 Data Collection

Disease severity data was collected following inoculation when the first symptoms appeared (2 August 2019) and continued weekly from August through September on the basis of percentage plot area exhibiting disease symptoms (0= no disease to 100= 100%) (Boulter et al. 2002). Turf color data was collected on 23 June in both locations. Turfgrass color was rated based on the estimation scale with 1 = brown poor quality or dead turf, 6 = minimally acceptable turf, and 9 = uniform, optimum green color turf using the National Turfgrass Evaluation Protocol (NTEP) rating system. AUDPC was calculated for each treatment using disease severity nd th ratings from August 2 to September 13 using the equation: AUDPC = Σni-1i=1 ([yi

+ y(i + 1)] / 2) (ti+1) - ti), where yi is the disease severity at the ith rating date, ti is the day of the ith rating and n is the total number of evaluation (Campbell and Madden, 1990). Normalized difference vegetation index (NDVI) was measured using a Greenseeker optical sensor, model 505 (Ntech Industries Inc., Ukiah CA, USA). NDVI ratings were taken every 12-22 day intervals from both locations starting on 22 July. Soil microbial respiration and SOM were measured twice, first before inoculating the plots and second at the end of the study. The dates for SOM measurements were 19 August and 19 September 2019.

2.2.2.10 Statistical Analyses

All statistical analyses were performed using SAS, University Edition, Version 9.4, Cary, NC, using Proc Glimmix (Generalized Linear Mixed Model). The experiment design was a split-plot with 9x2 factorial arrangements for RCBD. “Covtest” option was included to determine if the random effects were significant from zero or not. The data set was analyzed using repeated measures to determine the time-by-treatment interactions for disease severity, turf color, NDVI and SOM parameters. The random effect was “block”. The “compound symmetry (cs)” option was selected better for repeated effects for covariance structure. The means were separated using the Tukey-Kramer method (command; pdiff lines) in the “lsmeans” statement at the significance level of P<0.05. The normality assumption was also checked to assess the fit of the data.

3 Results

3.1 Greenhouse Study 1

3.1.1 The Effects of Soil Conditioner Treatments on Dollar Spot Severity

There were no significant differences in disease severity between any treatments from 7 DAI (days after inoculation) to 21 DAI. However, chlorothalonil- treated turf had significantly lower severity than any other treatments (Table 3.1) and this trend was observed until 35 DAI. While the severity continued to increase in all soil conditioner-treated pots by 35 DAI, SMC and WC-treated pots showed significantly higher levels of disease severity than the other pots, including the negative control, urea. By 42 DAI, there was a numerical decrease in disease severity in all the treatments, except WC and FE+WC treatments; however, all soil conditioners provided statistically equal or higher disease severity than urea. Although recovery was evident in the treatments listed above, soil conditioners did not provide satisfactory dollar spot control when compared with urea. SMC and WC exhibited increased disease severity compared to all other treatments while chlorothalonil successfully suppressed dollar spot better than all treatments except AWCT+urea and AWCT+urea+FH at 49 DAI, which were both comparable to the positive control, chlorothalonil by the end of the study (Table 3.1).

Table 3.1: The effects of soil conditioner treatments on dollar spot severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height of cut (6mm) in GH study 1 in Guelph, ON, in 2019

Disease severity (%)z Treatmenty 7 DAIx 14 DAI 21 DAI 28 DAI 35 DAI 42 DAI 49 DAI SMC 10.0aw 15.0a 25.0a 52.0a 74.0a 67.0ab 72.0a WC 7.0a 13.0a 26.0a 52.0a 73.0a 76.0a 65.4a AWCT+urea 8.0a 12.0a 21.0a 20.0b 25.0c 16.0ef 7.0de FH 9.0a 13.0a 23.0a 35.0b 55.0b 52.0bc 46.0b FE+WC 12.0a 19.0a 27.0a 25.0b 51.0b 65.0ab 43.0bc FE 7.0a 14.0a 23.0a 29.8b 49.0b 42.0cd 18.0bc AWCT+urea+FH 9.0a 17.0a 24.0a 34.0b 50.0b 25.0de 12.0de urea (control) 9.0a 15.0a 24.0a 22.0b 36.0bc 27.0de 25.0cd chlorothalonil+ureav 3.0a 3.0a 3.0b 3.0c 5.0d 6.0f 6.0e z First disease severity data was collected on 3 July (7 DAI) and thereafter every 7 days according to Boulter et al. (2001) with 0% = no disease and 100= 100% of the plot area exhibiting disease symptoms. y Fertilizer treatment applications began on 14 May and were applied for 6 weeks before inoculation. Pots were inoculated with C. jacksonii on 25 June and symptoms appeared within one week. SMC= spent mushroom compost, WC= worm castings, (AWCT+urea) = aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate x DAI= Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil treatment was applied the day before the fertilizer treatment applications.

3.1.2 The Effects of Soil Conditioner Treatment on AUDPC

None of the soil conditioner treatments suppressed dollar spot disease when compared with the negative control, urea. AWCT+urea, FE and AWCT+urea+FH treatments did not differ in AUDPC values compared to urea (Figure 3.1). However, FE+WC treatments increased the AUDPC of dollar spot compared with AWCT+urea, chlorothalonil and urea. The significantly higher AUDPC value of dollar spot was observed in WC-treated pots among all treatments; however, it did not differ from SMC. The positive control, chlorothalonil, had the lowest cumulative disease severity, showing the lowest AUDPC among all treatments (Figure 3.1).

2000 a ab

bc 1500 cd

cd cd de 1000 e

500 f

0 AUDPC disease AUDPC spot fordollar

3.1.3 The Effects of Soil Conditioner Treatments on Turf Color

The turf color data showed significant treatment effects on each rating date. The first turf color data was collected on 25 June, on the day of inoculation. The

darkest turf color was obtained from chlorothalonil, urea, FE and AWCT+urea among all treatments (Table 3.2). The rest of the treatments did not lead to enhanced turf color compared with urea. After the inoculation, the turf color decreased in all the treatments by 10 DAI, with AWCT+ urea, FE and chlorothalonil having acceptable turf color (>6.0) which shows that led to similar to urea treatment. SMC, WC, FH, FE+WC and AWCT+urea+FH treatments exhibited significantly reduced turf color compared with urea. A similar treatment effect from these treatments was evident at 20, 30 and 40 DAI. However, AWCT+urea+FH - treated plots showed little color improvement at 20 DAI compared to 10 DAI. Occurrences of improved turf color observed at 20 DAI were statistically similar for urea over the entire season. Similarly, after 10 DAI, AWCT+urea, FE, AWCT+urea+FH and urea-treated turf maintained above acceptable turf color (>6.0) for longer than the other soil conditioner treatments. However, these soil conditioner effects on turf color were similar to those observed in urea-treated plots (Table 3.2). SMC applied pots had significantly poorer turf color than all treatments except WC treatment (Table 3.2).

Table 3.2: The effect of soil conditioner treatments on turf color severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height of cut (6mm) in GH Study 1 in Guelph, ON, in 2019

Turf color (1-9)z Treatmenty Pre-inoculation 10 DAIx 20 DAI 30 DAI 40 DAI SMC 5.8cw 4.6e 3.2c 2.5d 2.4e WC 6.0bc 4.7e 3.4c 2.5d 2.8de AWCT+urea 7.9a 7.0bc 6.6b 6.5b 6.6b FH 6.8b 6.2dc 5.3c 4.5c 4.5c FE+WC 6.3bc 6.0d 5.7c 3.0d 3.4d FE 8.0a 7.2b 6.7b 6.2b 6.2b AWCT+urea+FH 6.0bc 5.8d 6.1b 6.1b 6.0b urea (control) 8.3a 7.9ab 6.7b 6.5b 6.6b chlorothalonil+ureav 8.8a 8.2a 8.3a 8.5a 8.3a z Turf color ratings were taken every 14 days according to the rating system designed by the National Turfgrass Evaluation Program (NTEP) on a scale of 1 to 9 with 9 = darkest green color, 6=minimum acceptable color, 1= completely straw-brown color turf y Fertilizer treatment applications began on May 14 and were applied for a 6-week period before inoculation. The first turf color data were taken on June 25 before inoculation and then pots were inoculated with C. jacksonii on the same day. SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate x DAI=Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05). v The chlorothalonil was applied on the day before the fertilizer treatment applications.

3.1.4 The Effects of Soil Conditioners on Root Dry Weight

The effects of the fertilizer treatments had no positive effect on root biomass at 0-5, 5-10 and 10+ cm depths. No soil conditioner treatment differences were observed when compared with urea, However, chlorothalonil had significantly higher root mass than SMC and WC treatments at 0-5 cm depth (Table 3.3). A similar pattern was also observed at 10+ cm depths. At 5-10 cm depts, there were no significant differences between any of the treatments. Regarding total root mass, the application of SMC and WC caused significantly reduced root biomass compared to all other all treatments. The greatest biomass was produced from the chlorothalonil treatment. Total root biomass from AWCT+urea, FH, FE+WC, FE and AWCT+urea+FH did not differ from urea (Table 3.3).

Root biomass (g)z Treatmenty 0-5 cm depth 5-10 cm depth 10+ cm depth Total (g) SMC 0.26bx 0.29a 0.55b 1.14c WC 0.27b 0.30a 0.62b 1.17c AWCT+urea 0.51ab 0.28a 0.80ab 1.63b FH 0.62ab 0.28a 0.81ab 1.76b FE+WC 0.63ab 0.28a 0.50ab 1.44b FE 0.53ab 0.28a 0.82ab 1.58b AWCT+urea+FH 0.52ab 0.31a 0.82ab 1.72b urea (control) 0.63ab 0.34a 0.79ab 1.78ab chlorothalonil+urea 0.83a 0.33a 0.97a 2.17a z Roots were harvested in the end of the experiment. y SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate x Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05).

3.1.5 The Effects of Soil Conditioners on Clipping Yield

Clipping dry weight of creeping bentgrass treated with soil conditioners were the same or lower than those treated with urea (Figure 3.2). AWCT+urea, chlorothalonil, AWCT+urea+FH, FE and urea treated pots had similar clipping yields. However, compared with these treatments and urea, FH and FE+WC showed reduced clipping dry weight. The significantly lowest clippings were produced from SMC and WC-treated pots compared with all treatments (Figure 3.2). Additionally, a strong positive correlation between tissue N rate and clipping weight was obtained (r=0.92 p=0.004) (Figure 3.3)

100

) 2 a a a a a 80 b b 60

c 40 c

Dry weight clippings / cm clippings (mgDry weight 20

R2= 0.84

ipping dry weight dry ipping Cl

95 % Prediction limits, Fit, 95 % Confidence Limits

Tissue N concentration (%)

Figure 3.3: The relationship between tissue N concentration and clipping dry weight of creeping bentgrass ‘Penn A-4’ maintained as fairways height of cut (6mm) in GH 1 in Guelph, ON, in 2019.

3.1.6 The Effects of Soil Conditioner Treatments on Tissue Nitrogen Concentration of Creeping Bentgrass

The tissue N concentration of AWCT+urea, AWCT+urea+FH, FE and chlorothalonil treatments did not significantly differ from that of urea (Figure 3.4). Significantly reduced N levels in leaf tissue were observed under FH and FE+WC treatments compared with urea. The turf treated with SMC and WC produced the lower level of N in leaf tissue than all treatments (Figure 3.4). Additionally, the

negative correlation coefficient demonstrated a strong relationship between tissue N and AUDPC of dollar spot (r= -0.90, P=0.0008). (Figure 3.5)

a a a 3 a a b b c 2 c

% rate N % dry 1

R2= 0.81

AUDPC

95 % Prediction limits, Fit, 95 % Confidence Limits

Tissue N concentration (%)

Figure 3.5: The relationship between tissue N concentration and AUDPC of creeping bentgrass ‘Penn A-4’ maintained as fairways height of cut (6mm) in GH 1 in Guelph, ON, in 2019.

3.2 Greenhouse Study 2

3.2.1 The Effects of Soil Conditioner Treatments on Dollar Spot Severity

No significant differences were observed between soil conditioner and urea treated pots on disease severity from 7 DAI to 14 DAI (Table 3.4). Although chlorothalonil treatment effect did not differ from any of the treatments at 7 DAI, it only showed significant difference compared with WC. The chlorothalonil effect became prominent at 14 DAI, indicating that it significantly reduced dollar spot compared with all treatments. At 21 DAI, the dollar spot severity in the soil conditioner-treated pots decreased, but none of the treatments showed significant disease reduction compared with urea. In contrast, the SMC treatment led to significantly higher

disease severity than other treatments, except for WC. AWCT+urea, FE+WC, FE, AWCT+urea+FH showed equal control of dollar spot compared with urea; however, significantly higher disease severity was observed with half-rate urea and FH-treated pots compared with urea. After 21 DAI, disease severity generally continued to increase numerically until 42 DAI for all treatments except the AWCT +urea + FH treatment. However, the numerical decrease in disease severity in the pots treated with AWCT+urea+FH treatment was not statistically different from negative control, urea at 42 DAI. Similarly, SMC- treated pots had significantly higher disease severity than all other treatments, except for 28 DAI, where there was no difference between SMC and WC. FH-treated pots continued to have significantly higher disease severity than any other soil conditioner treatments except for WC at 28 DAI. By 35 DAI, disease became significantly severe in SMC and WC-treated pots as they showed the highest disease severity until the end of the study when compared with other fertilizer treatments. FH, FE+WC and AWCT+urea+FH treatments had significantly higher disease severity compared with urea at 35 DAI. On the same day, urea-treated pots showed significant less disease severity than the FH and AWCT+urea - treated pots. The effect of FH and AWCT+urea+FH treatments provided equal control when compared with urea at 42 DAI.

Although severity decreased in AWCT+urea+FH - treated pots at 42 DAI, there were no significant differences between urea and AWCT+urea+FH. From 42 DAI to 49 DAI, pots that received AWCT+urea, FE+WC, FE, AWCT+urea+FH and half-rate urea began to recover from disease injury; however, none of the soil conditioners significantly differed from urea in disease severity. The application of chlorothalonil led to consistently low dollar spot severity during the entire study when compared with all other treatments (Table 3.4).

Table 3.4 The effects of soil conditioners on dollar spot severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height (6mm) in GH study 2 in Guelph, ON, in 2019

Disease severity (%)z Treatmenty 7 DAIx 14 DAI 21 DAI 28 DAI 35 DAI 42 DAI 49 DAI SMC 9.0abw 31.0a 35.0a 48.0a 56.0a 56.0a 64.0a WC 12.0a 29.0a 30.0ab 45.0ab 57.0a 58.0a 72.0a AWCT+urea 6.0ab 28.0ab 16.0cd 28.0de 34.0cde 35.0de 31.0d FH 10.0a 26.0ab 22.0bc 38.0bc 36.0bc 45.0bc 52.0b FE+WC 9.0ab 32.0a 17.0cd 23.0e 35.0bc 52.0cde 42.0c FE 8.0ab 19.0b 11.0de 27.0de 25.0d 31.0e 28.0d AWCT+urea+FH 6.0ab 26.0ab 20.0cd 34.0cd 40.0b 36.0cde 33.0cd urea (half rate) 7.0ab 25.0ab 22.0bc 26.0de 29.0cde 43.0bcd 31.0d urea (control) 5.0ab 24.0ab 14.0de 26.0de 26.0de 37.0cde 27.0d chlorothalonil+ureav 3.0b 3.0c 2.0f 1.0f 2.0f 2.0f 2.0e z First disease severity data were collected on 30 September (7 DAI) and thereafter every 7 days, according to Boulter et al. (2001) with 0% = no disease and 100= 100% of the plot area exhibiting disease symptoms y Fertilizer treatment applications began on 12 August and were applied for six weeks before inoculation. Pots were inoculated with C. jacksonii on 23 September. Symptoms appeared within almost one week after inoculation. SMC= spent mushroom compost, WC= worm castings, (AWCT+urea) = aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate x DAI=Days After inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil was applied on the day before the fertilizer treatments.

3.2.2 The Effects of Soil Conditioner Treatments on AUDPC

The chlorothalonil-treated pots, which had the lowest AUDPC, showed significantly reduced dollar spot compared with all other treatments (Figure 3.6). In contrast, SMC and WC-treated pots had the highest disease accumulation throughout the study. The AUDPC values of dollar spot in AWCT+urea and FE treatments were significantly lower than that of FH and FE+WC. The FE treatment led to significantly lower AUDPC than observed with all the other soil conditioners. Although the AUDPC of FE was numerically lower than AWCT+urea and urea, the AUDPC of FE, AWCT+urea and urea did not differ from AUDPC value of urea (Figure 3.6).

2000 a a

b 1500 a a bc cd cd de ef f 1000 a a

ef 500 a a

AUDPC disease AUDPC spot fordollar ef a a 0

ef a a

ef a a Figure 3.6: The effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) for rating between 30 September and 11 November in GH study 2 in Guelph, ON, in 2019.ef Pots were inoculated with C. jacksonii on 23 Septembera and the first symptoms began to appear on 30 September. AUDPC was calculated fora each treatment using the equation: AUDPC = Σni-1i=1 ([yi + y (i + 1)] / 2) (ti+1) - ti), where yi is the disease severity at the ith rating date, ti is the day of the ith rating and n is the total number of evaluation (Campbell and Madden, 1990). Chlorothalonil was applied the day before the soil conditioner treatmentsa at 14-day intervals. Bars with the same letter for eachef fertilizer treatments are not significantlya different according to Tukey-Kramer method (α ≤ 0.05)

a ef a

63 a ef a

3.2.3 The Effect of Soil Conditioner Treatments on Turf Color

In the pre-inoculation period, all treatments had at or above acceptable turf color (>6.0) (Table 3.5). SMC and WC – treated pots exhibited the lowest turf color compared with all fertilizer treatments. Color ratings from FE, AWCT+urea, half-rate urea, urea, and chlorothalonil treatments were significantly greater than FE+WC and AWCT+urea+FH treatments. None of the soil conditioners led to improved turf color when compared with urea. After inoculation, there was a decrease in turf color in pots treated with soil conditioner treatments until 30 DAI. SMC and WC treatments had reduced turf color compared to all other treatments as early as 10 DAI. No other significant differences were observed among soil conditioner treatments compared with urea at 10 DAI. Again, there were no significant differences between soil conditioners and urea, except the pots treated with SMC at 20 DAI, which had significantly poor turf color. By 30 DAI, SMC and WC-treated pots showed significantly reduced turf color compared to all other treatments except FE+WC. At 40 DAI, there was an improvement in turf color (>6.0) in pots treated with AWCT+urea, AWCT+urea+FH and FE. However, this improvement was not statistically different from the urea-treated pots. Turf treated with AWCT+urea and half-rate urea had also similar turf color to urea at 40 DAI. Turf color in FH, FE+WC, half-rate urea, SMC and WC-treated pots showed significant decline compared with the treatments of AWCT+urea, FE, AWCT+urea+FH and urea. However, turf color obtained from FH and FE+WC treatments did not differ from the turf color produced under the treatments of WC and half-rate urea. SMC treatment resulted in the poorest turf color among all treatments, except WC. The darkest turf color was obtained from chlorothalonil at 40 DAI (Table 3.5).

Table 3.5 : The effects of soil conditioner treatments on turf color severity in ‘Penn A-4’ creeping bentgrass maintained at fairway height (6mm) in GH study 2 in Guelph, ON, in 2019

Turf color (1-9) z Treatmenty Pre-Inoculation 10 DAIx 20 DAI 30 DAI 40 DAI SMC 6.0dw 5.0d 4.1c 3.6e 3.1e WC 6.1d 5.2d 5.0bc 3.7e 3.5de AWCT+urea 7.9ab 6.7bc 6.0ab 6.4b 6.4b FH 7.7abc 6.2c 5.8b 4.9cd 4.6cd FE+WC 7.5bc 6.2c 5.4b 4.2de 4.6cd FE 8.8a 7.5ab 6.2ab 6.0bc 6.2b AWCT+urea+FH 7.4c 6.5c 6.1ab 6.1bc 6.2b urea (half rate) 7.4abc 6.4c 5.8b 5.8bc 5.5bc urea (control) 8.3ab 7.0bc 6.0ab 6.0bc 6.5b chlorothalonil+urea v 8.7ab 8.1a 7.1a 7.9a 7.8a z Turf color ratings were taken every 14 days according to the rating system designed by the National Turfgrass Evaluation Program (NTEP) on a scale of 1 to 9 with 9 = darkest green color, 6=minimum acceptable color, 1= completely straw-brown color turf y Soil conditioner applications began on 12 August and were applied for six weeks before inoculation. The first turf data were taken on 23 September before inoculation and then pots were inoculated with C. jacksonii on same day. SMC= spent mushroom compost, WC= worm castings, (AWCT+urea) = aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate x DAI=Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil treatment was applied on the day before the fertilizer treatment applications.

3.2.4 The Effects of Soil Conditioners on Root Dry Weight

None of the soil conditioner treatments had a positive effect on root biomass at 0-5, 5-10 and 10+ cm depts. No differences among treatments were observed, with the exception of chlorothalonil and AWCT+urea which had significantly higher root mass than SMC and WC treatments at 0-5 cm depth. (Table 3.6). A similar pattern was observed at 10+ cm depths. At 5-10 cm depts, there were no significant differences between any of the treatments. Regarding total root mass, the greatest biomass was produced from chlorothalonil, AWCT+urea and urea. In contrast, the lowest root biomass production was obtained from SMC and WC-treated turf among all treatments; however, the total biomass produced under the treatments of SMC and WC did not differ from the root biomass of FH treatment. Treatments receiving FH, FE, FE+WC, AWCT+urea+FH resulted in lower root biomass than urea (Table 3.6).

Root biomass (g)z Treatmenty 0-5 cm depth 5-10 cm depth 10+ cm depth Total (g) SMC 0.27bx 0.19a 0.37b 0.82d WC 0.26b 0.25a 0.35b 0.85d AWCT+urea 0.61a 0.19a 0.69a 1.50a FH 0.36ab 0.20a 0.42ab 1.02cd FE+WC 0.35ab 0.21a 0.46ab 1.04c FE 0.36ab 0.20a 0.47ab 1.06c AWCT+urea+FH 0.53ab 0.23a 0.55ab 1.33b urea (control) 0.62ab 0.17a 0.68a 1.51a urea (half rate) 0.53ab 0.17a 0.54ab 1.27b chlorothalonil+urea 0.65a 0.21a 0.68a 1.56a z Roots were harvested in the end of the experiment y SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate x Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05)

3.2.5 The Effects of Soil Conditioner Treatments on Clipping Yield

None of the soil conditioner treatments produced higher clipping yield than those treated with urea (Figure 3.7). SMC and WC treatments had the lowest clippings. Similar clipping yields were obtained from chlorothalonil, AWCT+urea and AWCT+urea+FH and FE. The clipping production was numerically lower in FH and FE+WC treatments compared with FE; however, they did not differ from each other statistically. The turf treated with FH, FE+WC and half-rate urea had similar clipping dry weight, but they had significantly reduced clippings compared with urea (Figure 3.7). Additionally, a strong positive correlation between tissue N rate and clipping weight was obtained (r=0.93 p<.0001). (Figure 3.8)

120 a

) ) 2 100 a a ab a a 80

60 bc bc c a 40

d d 20 a 0

Dry weight of clippings clippings ( cm Dry/ mg weight of

Figure 3.7: The effects of soil conditioner treatments on dry weight of clippings in creeping bentgrass ‘Penn A-4’ maintained as fairway height of cut (6mm) in GH study 2 in Guelph, ON, in 2019.The application of soil conditioner treatments began on 12 August, then pots were inoculateda with C. jacksonii on September 23. The clippings were collected at the end of the study on 12 November. Bars with the same letter for each fertilizer treatments are not significantly different according to Tukey-Kramer method (α ≤ 0.05).

68 a

R2=0.86

Clipping dry weight dry Clipping

95 % Prediction limits, Fit, 95 % Confidence Limits

Tissue N concentration (%)

Figure 3.8: The relationship between tissue N concentration and clipping dry weight of creeping bentgrass ‘PennA-4’ maintained as fairways height of cut (6mm) in GH 2 in Guelph, ON, in 2019.

3.2.6 The Effects of Soil Conditioner Treatments on Tissue Nitrogen Concentration of Creeping Bentgrass

The tissue N concentration of AWCT+urea, FE, AWCT+urea+FH and chlorothalonil treatments did not differ from those obtained in urea-treated pots (Figure 3.9). The pots treated with SMC had the lowest tissue N concentration among all treatments, except WC. The treatment of WC, which had the second lowest N content, was not statistically significant from half-rate urea. The effect of FH and FE+WC treatments on tissue N concentration did not differ from that of the treatment of half-rate urea; however, FH, FE+WC and half-rate urea showed significantly reduced N concentration compared with urea (Figure 3.9). Additionally, the negative

correlation coefficient demonstrated a strong relationship between tissue N and AUDPC of dollar spot (r= -0.79, P=0.059). (Figure 3.10)

5 a ab ab ab a 4 bc c cd 3 de e

2 % dry N rate N % dry 1

R2=0.63

AUDPC

95 % Prediction limits, Fit, 95 % Confidence Limits

Tissue N concentration (%)

Figure 3.10: The relationship between tissue N concentration and AUDPC dollar spot on creeping bentgrass ‘Penn A-4’ maintained as fairways height of cut (6mm) in GH 2 in Guelph, ON, in 2019

3.3 Field Study 1

3.3.1 GRS 1 (Guelph Research Station 1) Trial

3.3.1.1 The Effects of Soil Conditioners and Rolling Treatments on Dollar Spot Severity

In the field study at the GRS 1 site, there was a significant 2-way interaction between soil conditioner and day on dollar spot severity (Appendix Table C3. 1). Within ten days after inoculation of the plots (10 DAI), dollar spot developed quickly in all plots and subsequently became very severe throughout the period of 7 weeks, except in the chlorothalonil-treated plots which had no symptoms of the disease. The responses of all soil conditioner-treated plots to dollar spot severity were similar to that of urea treatments, except for the SMC and WC treatments at 10 DAI (Table 3.7).

The severity trend was similar at 17 DAI compared to 10 DAI when there were no notable differences between the soil conditioner treatments in reducing dollar spot severity compared with urea, again except for the plots treated with SMC and WC, which showed significantly higher disease severity. At 24 DAI, no differences were observed among the effects of soil conditioner treatments on dollar spot severity. A significant increase in disease severity occurred from 31 DAI until 52 DAI. At 31 DAI, SMC, WC, FH and AWCT+urea+FH-treated plots had significantly higher disease severity than urea-treated plots whereas AWCT+urea, FE+WC and FE showed equal control compared to urea. By 38 DAI the dollar spot severity in all soil conditioner treatments was significantly higher than urea except for the WC- treated plots; however, disease severity in these plots doubled by 45 DAI and remained significantly higher than urea for the duration of the study. The increase in disease severity in WC-treated plots was higher than all of the other soil conditioner treatments, except SMC-treated plots which exhibited similar control to WC treatment at 45 DAI. Similarly, dollar spot was significantly higher in FH, FE+WC, FE and AWCT+urea+FH - treated plots when compared with urea.

However, the effect of AWCT+urea application was similar to that of urea at 45 DAI. Dollar spot injury peaked at 52 DAI with the most severe disease occurred in SMC and WC-treated plots. None of the soil conditioners suppressed the dollar spot compared with urea. Even though the dollar spot severity in urea and AWCT+urea- treated plots increased at 52 DAI, their effect was not statistically significant. Chlorothalonil significantly suppressed the dollar spot severity throughout the study (Table 3.7)

Table 3.7: The effects of soil conditioner treatments on dollar spot severity in ‘Penn A-4’ creeping bentgrass putting greens at the GUELPH RESEARCH STATION 1 location, Guelph, ON, in 2019

Disease severity(%)z Treatmenty 10 DAIx 17 DAI 24 DAI 31 DAI 38 DAI 45 DAI 52 DAI SMC 13.0aw 25.5a 29.0a 35.6a 47.0ab 68.0ab 81.0a WC 11.0ab 23.1a 28.1a 33.1a 35.0cd 70.0a 83.0a AWCT+urea 6.7abc 18.5ab 19.0a 20.6ab 41.0abc 43.1c 54.0d FH 7.4abc 21.0ab 28.0a 33.1a 42.0abc 56.0b 68.7c FE+WC 5.8bc 14.0b 24.0a 29.3ab 40.0bc 53.0b 73.7bc FE 6.5abc 18.4ab 28.0a 31.8ab 41.0bc 59.0b 78.7ab AWCT+urea+FH 8.0abc 21.0ab 23.0a 33.0a 48.7a 55.0b 66.0c urea (control) 3.3cd 13.5b 23.7a 15.7b 33.1d 44.3c 49.3d chlorothalonil+ureav 0.d 0.c 1.2b 0.c 1.2e 1.2d 1.8e z First disease severity data were collected on 10 July (7 DAI) and thereafter every 7 days according to Boulter et al. (2001) with 0% = no disease and 100= 100% of the plot area exhibiting disease symptoms y Fertilizer treatment applications began on 11 June. Pots were inoculated with C. jacksonii on 23 July after a 6-week fertilizer treatment application. Symptoms appeared within ten days after inoculation. SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate. SMC and WC treatments were top-dressed x DAI= Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05). v The chlorothalonil was applied the day before fertilizer treatment applications.

3.3.1.2 The Effects of Soil Conditioners and Rolling on AUDPC

The results showed that the AUDPC of dollar spot was significantly affected by the soil conditioner treatments. Neither the main effect of rolling nor the rolling by soil conditioner interaction was significant (Appendix Table C3. 3). Chlorothalonil did result in a considerably lower in dollar spot AUDPC compared with all treatments. All of the soil conditioners treatments had a higher AUDPC than urea (Figure 3.11). The dollar spot AUDPC was the highest with the application of SMC. WC plots had significantly higher AUDPC than AWCT+urea, FE+WC and AWCT+urea+FH and urea- treated plots; however, seasonal AUDPC of WC, FH and FE did not differ from one another other (Figure 3.11).

2000

a ab bc bc 1500 c c c d 1000

500

0 AUDPC disease AUDPC spot fordollar

3.3.1.3 The Effects of Soil Conditioners and Rolling on Turf Color

The results of our study demonstrated that there was a significant soil conditioner treatment by day interaction on turf color; however, the interaction of rolling by soil conditioner, rolling by day and rolling by day by soil conditioner were not significant (Appendix Table C3. 2). Overall, when compared with urea. Before inoculation, plots treated with AWCT+urea, FH, FE+WC, FE and AWCT+urea+FH exhibited above acceptable turf color (>6.0), showing no significant differences compared with urea (Table 3.8). SMC and WC had significantly poor turf color whereas the best response in turf color was from chlorothalonil-treated plots. After inoculation, there was no improvement in turf color in soil conditioner-treated plots compared with urea at 10 DAI. SMC, WC and FH treated plots showed significantly lower turf color than urea-treated plots. At 20 DAI, urea-treated plots maintained above acceptable turf color (>6.0) whereas AWCT+urea and AWCT+urea+FH- treated plots showed a decrease in turf color, producing similar turf color to urea. In contrast, SMC, WC, FH, FE+WC and FE-treated plots exhibited less than acceptable turf color (<6.0) compared with urea at 20 DAI. The turf color rating continued to decrease, and no turf color improvement was observed from 30 DAI to 50 DAI. The same trend in turf color response at 20 DAI was observed at 30 DAI from all soil conditioner-treated plots compared to urea-treated plots with the exception of the FE treatment which had similar turf color with urea-treated plots at 30 DAI. There were no significant differences between urea and soil conditioners in the enhancement of turf color from 40 DAI to 50 DAI. Turf color improved in AWCT+urea-treated plots at 50 DAI when compared to 40 DAI; however, this improvement was not statistically significant versus urea-treated plots. WC-treated plots had the poorest turf color among all treatments at 50 DAI. SMC treatment resulted in similar effect to FH, FE and WC. In contrast, chlorothalonil provided the darkest color throughout the study. None of the soil conditioners enhanced the turf color over time (Table 3.8).

Table 3.8: The effects of soil conditioner treatments on turf color in ‘Penn A-4’ creeping bentgrass putting greens at the GUELPH RESEARCH STATION 1 location in Guelph, ON, in 2019

Turf color (1-9)z Treatmenty Pre-inoculation 10 DAIx 20 DAI 30 DAI 40 DAI 50 DAI SMC 5.7cw 5.8c 5.3c 5.2c 3.5c 2.8ed WC 5.7c 5.9c 5.5c 5.4c 3.3c 2.6e AWCT+urea 6.5bc 6.3bc 5.8bc 5.3b 3.9b 4.2bc FH 6.4bc 5.9c 4.8c 4.8c 3.8c 3.6cd FE+WC 6.0bc 6.0bc 5.2c 5.5c 3.5c 3.0bc FE 6.1bc 6.0bc 5.5c 5.4bc 3.9c 3.7cd AWCT+urea+FH 6.5bc 6.1bc 5.7bc 5.5b 3.5b 3.5c urea (control) 6.7b 6.6b 6.6b 6.1b 5.5b 4.5b chlorothalonil+ureav 8.0a 7.5a 7.8a 7.3a 7.5a 7.5a z Turf color ratings were taken every 14 days according to the rating system designed by the National Turfgrass Evaluation Program (NTEP) on a scale of 1 to 9 with 9 = darkest green color, 6=minimum acceptable color, 1= completely straw-brown color turf y Fertilizer treatment applications began on 11 June and were applied for six weeks. The first turf data were taken on 23 July before inoculation and then pots were inoculated with C. jacksonii on 23 July. SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate. x DAI=Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05). v The chlorothalonil treatment was applied the day before fertilizer treatment applications at a rate of 100 ml/ 100m2.

3.3.1.4 The Effect of Soil Conditioners and Rolling on NDVI

The results of the study demonstrated that there was no rolling by soil conditioner interaction effect on NDVI values but there were significant differences among soil conditioner treatments across the data collection dates (Appendix Table C3. 4). Before inoculation, soil conditioner treated plots showed the similar NDVI values to those treated with urea and chlorothalonil (Table 3.9). This similar pattern was observed among all treatments at 10 DAI. There was a decline in NDVI values in fertilizer treatments where the turf injury progressed rapidly from 22 DAI to 59 DAI. The NDVI values of soil conditioner-treated plots were either lower than or similar to that of urea-treated plots from 22 DAI to 59 DAI. The response of FE+WC and AWCT+urea on NDVI did not differ from that of urea application at 32 DAI. Additionally, urea and chlorothalonil treatments had equal NDVI values on the same day. After 32 DAI, while all soil conditioner treated plots showed significantly lower NDVI value than urea, the effect of AWCT+urea which was similar to urea maintained until 59 DAI. The poorest density of green leaves was obtained from SMC- and WC- treated plots compared with all treatments, except FH at 59 DAI. The NDVI value of chlorothalonil-treated plots showed the healthiest turf only from 32 DAI to 59 DAI.

NDVI z Treatmenty Pre-inoculation 10 DAIx 22 DAI 32 DAI 41 DAI 59 DAI SMC 0.555aw 0.570ab 0.516c 0.364e 0.198d 0.166d WC 0.549a 0.566ab 0.538bc 0.436cd 0.237de 0.194d AWCT+urea 0.571a 0.592ab 0.560bc 0.468bc 0.380b 0.348b FH 0.561a 0.583ab 0.525c 0.405de 0.239de 0.216cd FE+WC 0.566a 0.585ab 0.560bc 0.465bc 0.295c 0.258c FE 0.551a 0.587ab 0.553bc 0.437cd 0.286cd 0.252c AWCT+urea+FH 0.553a 0.594ab 0.553bc 0.430cd 0.285cd 0.257c urea (control) 0.587a 0.587a 0.587ab 0.499b 0.398b 0.367b chlorothalonil+ureav 0.591a 0.610a 0.613a 0.570a 0.653a 0.619a z Normalized difference vegetation index (NDVI) (0-1) indicates that 0= no green vegetation, close to +1 (0.8-0.9) = the highest possible density of green leaves y First NDVI readings were taken on 22 July after 6-week fertilizer treatment applications before inoculation and the measurement of NDVI was recorded at 12-20 days interval during the experimental period. Plots were inoculated with C. jacksonii on 23 July. SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate. x DAI=Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil treatment was applied the day before fertilizer treatment applications.

3.3.1.5 The Effects of Soil Conditioners and Rolling on SOM, Soil Aggregate Stability and Soil Microbial Respiration

In this study, it was hypothesized that soil conditioners will reduce dollar spot severity by increasing microbial activity and antagonism. The effects of soil conditioners on soil organic matter and soil aggregate stability were assessed based on ANOVA table shown in Appendix Table C and Appendix Table D, revealing that SOM and soil aggregate stability were not affected by soil conditioners. Neither main effects nor interaction effects of soil conditioners and rolling were found to be significant on SOM and soil aggregate stability. Microbial data were not available for both locations due to experimental error.

3.4 Field Study 2

3.4.1 GRS 2 (Guelph Research Station 2) Trial

3.4.1.1 The Effects of Soil Conditioners and Rolling Treatment on Dollar Spot Severity

In the field study conducted at the GRS 2 site, a significant effect of soil conditioners on dollar spot severity was observed. Additionally, there were significant 2-way interactions between rolling and day and soil conditioner and day (Appendix Table D4. 1). Rolling had an effect on disease severity over time on each rating date (Figure 3.12). There were no significant differences between rolled and unrolled plots from 10 DAI to 38 DAI. The significant differences were detected at 45 DAI and 52 DAI, where rolled plots had significantly lower disease severity than unrolled ones, when the disease pressure was high (Figure 3.12). There were no significant differences among the soil conditioner treatments from 10 DAI to 24 DAI during the time of low disease pressure. Chlorothalonil-treated plots had no dollar spot symptoms until 24 DAI (Table 3.10). Disease severity increased from 31 DAI through 38 DAI and plots treated with soil conditioners did not differ from urea until 45 DAI, except FE+WC-treated plots which had significantly higher disease severity at 31, 38 and 45 DAI. At 52 DAI, disease severity was significantly higher in the SMC-treated plots compared with the plots treated with urea and other soil conditioners, except for WC. The WC treatment had equivalent disease severity to FH, FE+WC and AWCT+urea+FH treatments; however, it showed significantly higher disease severity than AWCT+urea, FE and urea- treated plots. AWCT+urea and urea-treated plots

provided statistically similar dollar spot control. None of the soil conditioners were associated with reduced dollar spot severity when compared with urea. The most effective control was achieved by chlorothalonil among all treatments during the entire season (Table 3.10)

Table 3.10: The effects of soil conditioner treatments on dollar spot severity in ‘007’ putting greens at GUELPH RESEARCH STATION 2 location, Guelph, ON, in 2019

Disease severity (%)z Treatmenty 10 DAIx 17 DAI 24 DAI 31 DAI 38 DAI 45 DAI 52 DAI SMC 6.1aw 14.8a 15.6a 19.7ab 23.5ab 46.3bc 77.0a WC 6.4a 14.8a 14.6a 19.8ab 25.0ab 49.1bc 75.3ab AWCT+urea 6.7a 11.1a 12.8a 14.2ab 18.2ab 40.6cd 38.0d FH 5.8a 12.6a 13.1a 20.5ab 24.2ab 55.6ab 62.5bc FE+WC 7.1a 14.8a 15.5a 23.5a 29.3a 66.8a 70.6ab FE 6.6a 12.1a 12.2a 17.3ab 21.8ab 48.9bc 56.8c AWCT+urea+FH 3.9a 12.5a 13.3a 18.2ab 21.3ab 56.8ab 61.0bc urea (control) 6.6a 12.1a 11.5a 11.8b 14.7bc 36.5bc 36.2d chlorothalonil+ureav 0b 0b 0b 0.5c 4.6c 4.6e 5.1e z First disease severity data were collected on 10 July (7 DAI) and thereafter every 7 days according to Boulter et al. (2001) with percent 0% = no disease and 100= 100% of the plot area exhibiting disease symptoms y Fertilizer treatment applications began on 11 June. Plots were inoculated with C. jacksonii on 23 July one month after fertilizer applications. Symptoms appeared within 2 weeks after inoculation. SMC= spent mushroom compost, WC= worm castings, AWCT+urea= aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate. SMC and WC treatments were top-dressed. x DAI= Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil treatment was applied the day before the fertilizer applications at a rate of 100ml/ 100m2.

100 90 80 70 a 60 ab b 50 rolled 40 c unrolled 30 d de de 20 efg efg efg def

Dollar spot severity severity (%) spot Dollar efg 10 g fg 0 10 17 24 31 38 45 52

DAI

3.4.1.2 The Effects of Soil Conditioners and Rolling on AUDPC

Rolling had no effect on the AUDPC of dollar spot. The interaction effect of rolling by soil conditioner was not significant (Appendix Table D4. 3). None of the treatments were as effective as chlorothalonil in suppressing dollar spot (Figure 3.13). The urea treatment significantly suppressed the dollar spot compared with the soil conditioner treatments, except in the case of the AWCT+urea treatment. AUDPC levels also were significantly reduced by AWCT+urea and urea application compared to SMC and FE+WC (Figure 3.13).

2000

1500 a a ab ab ab ab bc 1000 c

500

d AUDPC for dollar spot dollar forAUDPC 0

3.4.1.3 The Effects of Soil Conditioners and Rolling on Turf Color

The results showed that turf color was significantly affected by the soil conditioner treatments. The interactions of rolling by day and rolling by fertilizers were significant (Appendix Table D4. 2.). Turf color in rolled plots did not differ from unrolled plots until 40 DAI (Figure 3.14). The significant differences between rolled and unrolled plots occurred only at 50 DAI, indicating that rolled plots had better turf color than unrolled ones (Figure 3.14). Before inoculation, there was no improvement in turf color by the soil conditioner treatments compared with urea. The turf color in AWCT+urea+FH-treated was similar to the turf color obtained by the urea treatment while the SMC-treated plots had significantly lower turf color than AWCT+urea and AWCT+urea+FH-treated plots (Table 3.11Table 3.10). Chlorothalonil-treated plots had the darkest turf. After inoculation, the turf color noticeably declined throughout the study and no turf color improvement was observed in the plots treated with the soil conditioners. At 10 DAI, AWCT+urea, AWCT+urea+FH and urea-treated plots showed acceptable (>6.0) turf color; however, the turf color exhibited as a result of these treatments did not differ from each other. Other soil conditioners provided

significantly lower turf color compared with urea. There was a similar trend in turf at 20 DAI where there was no improvement in turf color by soil conditioners compared with urea. The turf color continued to decrease in all soil conditioner treatments; however, AWCT+urea, FE, AWCT+urea+FH plots showed statistically similar turf color compared with urea. From 30 DAI to 40 DAI, AWCT+urea, FH, FE, AWCT+urea+FH treatments did not differ from urea. SMC, WC and FE+WC applications showed significantly poor turf color compared with urea. The plots treated by soil conditioners exhibited very poor turf color at 50 DAI. SMC and WC resulted in the poorest turf color compared with urea in this study. There were no significant differences among any of the soil conditioners. The darkest green color was obtained from chlorothalonil-treatments among all treatments over the season (Table 3.11).

9 8 7

a a ab ab ab bc 9) - 6 d d cd d d 5 e 4

3 Turf (1 color Turf 2 1

DAI

rolled unrolled

3.4.1.4 The Effects of Soil Conditioners and Rolling on NDVI

According to the findings of our study, there was no rolling by soil conditioner interaction for NDVI values. However, the main effects of both rolling and soil conditioner treatments on NDVI were significant (Appendix Table D4. 4). The NDVI values in rolled and unrolled plots were not significant before inoculation. After inoculation, there were no significant differences in NDVI at any rating date between rolled unrolled plots, except 41 DAI where rolled plots had significantly higher NDVI values than unrolled plots (Figure 3.15).

Before inoculation, no differences were observed in NDVI values between any of the soil conditioner treatments compared to urea treated plots. Plots that included urea (AWCT+urea+FH and AWCT+urea) did have similar NDVI values to both negative and positive control (Table 3.12). The decrease in NDVI values by all soil conditioner treatments was evident after the inoculation (at 10 DAI). After 10 DAI, the plots were severely damaged by dollar spot throughout the study and the NDVI values from soil conditioner-treated plots were either similar to or lower than those obtained from urea-treated plots. SMC, WC, FH, FE and FE+WC treated plots had significantly lower NDVI than AWCT+urea, AWCT+urea, urea and chlorothalonil treated plots at 10 DAI. These treatment differences observed at 10 DAI also existed in the plots that contained urea at 22 DAI. However, FE treated plots did not differ from urea at 22 DAI. From 22 DAI to 32 DAI, AWCT+urea-treated plots exhibited an NDVI response similar to urea. While plots receiving SMC and WC had the least healthy turf among all treatments from during 22 DAI and 32 DAI, WC application resulted in the lowest NDVI value at 41 DAI which did not statistically differ from SMC treatment. It was observed that none of the soil conditioner treatments led to higher NDVI values compared with urea until the end of the study. NDVI values in the chlorothalonil-treated plots remained relatively steady throughout the study and were significantly higher than all of the other treatments from 22 DAI to the end of the study (Table 3.12).

Table 3.11: The effect of soil conditioner treatments on turf color in ‘007’ creeping bentgrass putting greens at GUELPH RESEARCH STATION 2 location in Guelph, ON, in 2019

Turf color (1-9)z Treatmenty Pre-inoculation 10 DAIx 20 DAI 30 DAI 40 DAI 50 DAI SMC 5.3ew 5.0e 4.7d 3.6c 3.7cd 3.1c WC 5.5de 5.1de 4.6d 3.3c 3.5d 2.8c AWCT+urea 6.1cd 6.1bc 5.8bc 4.8b 4.9bc 4.3bc FH 5.7de 5.5de 5.0cd 4.0bc 4.0bcd 3.2bc FE+WC 5.6de 5.5cde 5.0cd 3.5c 3.7cd 3.3bc FE 5.9cde 5.6cd 5.5bcd 4.3bc 4.4bcd 3.6bc AWCT+urea+FH 6.6bc 6.1bc 5.7bc 4.1bc 4.5bcd 3.6bc urea (control) 7.2b 6.5b 6.3b 5.1b 5.2b 4.8b chlorothalonil+ureav 8.8a 9.0a 9.0a 9.0a 8.6a 7.6a z Turf color ratings were taken every 14 days according to (1-9) of NTEP; 9 representing the darkest green color, 6=minimum acceptable color, 1= completely straw-brown color turf y Fertilizer treatment applications began on 11 June and were applied for one month. The first turf data were taken on 23 July before inoculation and then pots were inoculated with C. jacksonii on 23 July. SMC= spent mushroom compost, WC= worm castings, (AWCT+urea) = aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate. x DAI=Days After Inoculation w Means within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil treatment was applied the day before the soil conditioner applications at a rate of 100 ml/ 100m2.

NDVI z Treatmenty Pre-inoculation 10 DAIx 22 DAI 32 DAI 41 DAI SMC 0.430bw 0.358c 0.172e 0.190f 0.123ed WC 0.428b 0.361c 0.189e 0.180f 0.084e AWCT+urea 0.518ab 0.485a 0.473b 0.469b 0.351b FH 0.446b 0.394bc 0.270d 0.251e 0.143d FE+WC 0.458b 0.393c 0.266d 0.261e 0.145d FE 0.468bc 0.427b 0.354c 0.353d 0.205c AWCT+urea+FH 0.519ab 0.479a 0.411b 0.415c 0.234c urea (control) 0.547a 0.504ab 0.493b 0.502b 0.386b chlorothalonil+ureav 0.550a 0.522a 0.573a 0.580a 0.654a z Normalized difference vegetation index (NDVI) (0-1) indicates that 0= no green vegetation, close to +1 (0.8-0.9) = the highest possible density of green leaves y First NDVI readings were taken on 22 July one month after soil conditioner applications before inoculation and the measurement of NDVI was recorded at 12-20-day intervals during the experimental period. Plots were inoculated with C. jacksonii on 23 July. SMC= spent mushroom compost, WC= worm castings, (AWCT+urea) = aerated worm castings tea+ urea, FH= fish hydrolysate, FE+WC=fish emulsion + worm castings, FE = fish emulsion, AWCT+urea+FH= aerated worm castings tea +fish hydrolysate. x DAI=Days After Inoculation w Mean within each column followed by the same letter are not significantly different according to Tukey-Kramer method (α ≤ 0.05) v The chlorothalonil was applied the day before the fertilizer applications.

0.6

a 0.5 a b b

0.4 c c c c

0.3 d

NDVI rolled e unrolled 0.2

0.1

0 Pre-inoculation 10 22 32 41

DAI

4 Discussion

4.1 Greenhouse Studies

Two greenhouse studies revealed that the soil conditioners were not able to reduce dollar spot when compared to urea negative control or to the chlorothalonil positive control. In fact, SMC and WC treatments enhanced the dollar spot severity compared to the synthetic fertilizer. These results were consistent in most of the individual disease severity ratings as well as throughout the season through the AUDPC values. The inability of the soil conditioners to offer a promising suppressive effect on disease occurred under conditions of both high and low disease pressure. The greenhouse study trials were conducted in different time periods and under different conditions; however, our results suggest that different environmental exposures from the different periods of time may not have been the factors affecting the outcomes. Previous research investigated the suppressive effects of organic fertilizers on dollar spot disease under various levels of disease pressure. Davis and Dernoeden (2002) found that the disease suppressive effect of nine organic N sources was not consistent from low to high disease pressure compared to urea and sulfur coated urea in a 3-year study. Nelson and Craft (1992) reported that the effect of brewery compost and poultry cow manure on dollar spot severity was inconsistent and did not persist under severe dollar spot pressure. Similarly, Kelloway (2012) also found that mink compost tea did not suppress the dollar spot under severe dollar spot conditions, but it reduced dollar spot under mild disease conditions. We had hypothesized that different forms of organic fertilizers/soil conditioners would offer more consistent reduction in disease development, but our data did not support this.

One potential reason why soil conditioners failed to suppress disease development could be associated with the N in soil conditioners which is not as readily available as it is in urea for plant uptake (Table 2.1). As shown in the analysis of the various conditioners, the proportion of water-insoluble nitrogen (WIN) was higher in most of the products than in the urea control. The reduced nitrogen availability, especially in the SMC and the WC treatments, may have led to higher dollar spot severity than in the urea-treated pots. Specifically, SMC and WC treatments had a much higher percentage of WIN, representing 92% and 96% of the

total N, respectively. It was observed that when SMC and WC were applied as a top dressing, the material was left on the surface of the canopy until the next evaluation date, which indicates that these materials might not have broken down, and turf may not have taken sufficient nitrogen as a result of nitrogen insolubility factor. Conversely, the reduced disease development with urea, both under low and high disease, is likely due to the more readily available N. Data from our study showed a significant difference in tissue N content between the treatments, with urea being equivalent to the fungicide positive control, and pots treated with SMC and WC having the lowest values (Fig 3.3 and 3.6). Previous work had reported that N availability is directly linked to dollar spot suppression (Davis and Dernoeden, 2002; Landshoot and McNiit, 1997; Beckley, 2018). Further evidence of the importance of nitrogen availability can be seen from the disease severity in the pots treated with FH alone versus those treated with AWCT+FH+urea. Our results showed a rise in disease severity when pots were treated with FH alone, while those treated with the combined conditioners treatments had equivalent final disease severity to the urea negative control in both GH studies. This might be due to the fact that since AWCT, which was derived from WC, does not contain nitrogen, the treatment had urea added to it as the sole source of nitrogen. Therefore, the effective component in AWCT was likely the urea. We thought that due to the similar source of both FH and FE, the addition of FH would have other positive effects on the plant (similar to what we would see with FE) leading to reduced disease development, but this was no supported by our data.

As mentioned above, similar to disease severity, the results indicated that the AUDPC of dollar spot was also not reduced under the soil conditioners when compared to the urea negative control. We were able to correlate tissue N levels to AUDPC and found that there was a negative correlation between the two in both GH studies. Above we suggested that N availability is an important indicator of dollar spot severity, but previous research also suggests that leaf tissue N levels can serve as a predictor for dollar spot severity. Research has shown that lack of sufficient N in the leaf tissue can increase the susceptibility of turf to dollar spot infection (Endo, 1966; Freeman, 1969; Watkins and Wit, 1995). As would be expected, low N availability would lead to reduced tissue N and this effect would be more visible over the course

of the growing season. As such, we would likely see increased disease development over time, as shown by the higher AUDPC values in the treatments that had reduced tissue N. Similar results were obtained from another study which found a strong negative correlation between N tissue content and dollar spot severity (Davis and Dernoeden, 2002). It was reported that the dollar spot disease of turfgrass was directly linked to plant N availability, meaning that the lack of sufficient N tended to increase infection of S. homoeocarpa. (Davis and Dernoeden, 2002; Endo, 1996; Landschoot and McNitt, 1997; Watschke, 1995). In our second greenhouse trial, the reduced nitrogen level in the half-rate urea treatment might have been the reason we saw an increase in dollar spot AUDPC values compared to the treatment with the full rate of urea. These results were also supported by the findings of Landschoot and McNiit (1997) and Couch (1995), which showed that the application of a high rate of N provided better dollar spot control than an application of a low N rate. It has been previously shown that as N level increases, dollar spot decreases (Liu et al., 1995; Burpee and Goulty, 1986). This effect is likely related to the fact that turf which received a higher rate of N recovered more quickly from disease injury than those which received low rate of N (Markland et al., 1969).

There was an assumption that FE would do at least as well as the urea, negative control due to the percent N availability in both products. However, we expected FE to perform better than urea as a result of microelements that FE might contain. Fish emulsion has been reported to contain Mg, S, Ca, Cu, Zn, Mn and Fe microelements (El-Tarabily et al, 2003). These microelements may have played a role in the response of turf to dollar spot disease, triggering plant defense mechanisms. Markland et al. (1969) suggested that high levels of iron, copper, and zinc in bentgrass tissues following an application of activated sewage sludge, were sufficient enough to inhibit S. homoeocarpa. It was also reported that micronutrients were able to control pathogen damage in plants either directly by antagonizing the pathogen or indirectly through enhancing plant defense mechanisms by systemic acquired resistance (Dutta et al, 2017). Another potential mechanism in the FE- treated pots is the release of volatile acids. Abbasi and Lazarovits (2006) looked at the use of FE to reduce potato scab and suggested that the mechanism of disease reduction in that study was possibly from toxicity of volatile fatty acids contained in

FE. In our study, however, FE was not more effective than urea, so additional studies are needed to further investigate whether micronutrients or other elements in FE could possibly have an effect on plant defense activation or direct antagonisms of pathogens.

One additional advantage of using FE could be a potential increase in microbial activity over time, leading to a suppressive effect of FE. In a study conducted by Abbasi et al. (2004), the researchers looked the suppressive effect of FE in damping- off disease on cucumbers. They reported that peat mix amended with 1%, 2% and 4% (m/m) FE showed highly effective control on damping off in cucumber seedlings. Specifically, with the 4% FE amendment, results indicated as much as 90% of the seedlings were disease-free. Another study also tested FE as a pre-planting soil amendment in micro plots and found that 1% FE added to the soil significantly reduced potato scab severity over the water control in multiple locations and soil types (Abbasi, 2006). In both cases, the researchers noted that the effect corresponded to an increased microbial activity over time. As the present study was conducted in a sterile sand rootzone mix, the microbial activity might not have played as great of a role in disease suppression. As we did not assess microbial activity in our GH studies, we were unable to confirm this as a possible effect of the addition of FE.

An interesting result from our study was that AWCT+ urea and AWCT+urea+FH treatments showed recovery from 42 DAI to 49 DAI in the first greenhouse study. At 42 DAI these treatments were no different from the urea negative control but did have higher disease severity than the chlorothalonil positive control. By 49 DAI, however, both the AWCT+urea and the AWCT+urea+FH had disease severity ratings that were no different from the fungicide control. It is important to note that these treatments also showed no difference from the urea negative control at 49 DAI, but the urea control was higher than the fungicide control and this was not the case with the two AWCT treatments. We are not certain why the recovery was seen, but it is important to note that disease severity in both of the AWCT treatments was significantly lower than in any of the other soil conditions treatments by 35 DAI. In our study, apart from N supply from urea, AWCT treatments of AWCT+urea and AWCT+urea+FH contained also molasses and it is possible that molasses might

have increased photosynthesis as it is a rapidly acquired source of energy and this might have increased the production of new leaf tissues, allowing the turf to out-grow the dollar spot injury. (Sanli et al., 2015; Pyakurel et al., 2019). Some studies reported that molasses increased soil organic carbon, nutrient level of soil, plant yield, vegetative growth parameters and photosynthetic pigments in some vegetables (Pyakurel et al., 2019; El- Tanahy and Fawzy, 2020). We must note, however, that this level of recovery was not observed in the second GH trial.

It is also known that soluble mineral nutrients, microorganisms, plant growth regulators extracted in vermicompost tea (another name for worm casting tea) affect plant growth (Edwards, 2006: Arancon; 2007). A vast amount of research on the effects of vermicompost tea relate plant growth and disease suppression to changes in microbial activity in both greenhouse and field scale experiments with different application methods (foliar spray and soil drench) and dilution levels (Scheuerell and Mahaffee, 2002; Conforti et al., 2002: Travis, 2003; Scheuerell and Mahaffee, 2004; Seddigh and Kiani, 2017). We did not measure microbial activity in growing media so unfortunately there is no real way to validate our result, but we could speculate that a certain level of microbial population and other nutrients in compost tea may have decreased vulnerability to pathogen infection. Future studies should identify the mechanisms responsible for this physiological change. Moreover, to better understand the effect of vermicompost tea on disease development, the nutrient composition of vermicompost that may have effect on physiological change on turf should further be investigated, and it is suggested that trial should be repeated more than twice.

Regarding turf color, our results demonstrated that soil conditioners resulted in either similar or lower color compared to urea in both greenhouse trials. When all treatments were compared to positive control, chlorothalonil, none of the treatments showed enhanced turf color. This might be related to the fact that the darker color turf has, the more efficient the N to be used since the readily available N present in urea and chlorothalonil probably account for faster color response than soil conditioners. It was reported that turfgrass color is correlated with higher levels of N in leaf tissue and the plants that have higher N levels produce a darker green color (Eguiza et al., 1991). Our results were in accordance with previous research Miller and Henderson,

2012; Beckley, 2018 those who founded that faster and darker color response from synthetic fertilizers treated plots than organic treatments. Similarly, Chen (2015) found that top dressing biosolids and yard trimming compost on turf was less effective in increasing quality than synthetic fertilizer. The previous research also confirmed the correlation between decreased disease severity and the dark green turf, indicating an association between N availability and dollar spot suppression (Landschoot and McNiit, 1997). The darkest turf color was obtained from with the treatment of chlorothalonil when the disease was present. This outcome was due to a combination of fungicide and readily available N from urea which contributed to the most effective dollar spot control. In other words, the control of dollar spot was enhanced by the pre-treatment of turf with chlorothalonil, resulting in preventing turf to be deficient from N.

Clipping weight is used as an indicator of overall plant health in terms of evaluation the fertilizer performance and it correlates mostly positively with tissue N (Carrow et al., 2001; Watson, 2009; Pease, 2011). Soil conditioners produced either lower than or similar to urea and chlorothalonil treatments at the end of the study. Our study was in agreement with Guertal and Green (2012) who conducted a 3- month study comparing organic fertilizers to inorganic fertilizers with only once application on creeping bentgrass. Clippings were collected twice throughout the study. It was found that, on both data collections dates, clipping yields in urea-treated plots was greater than those treated with organic ones. Similarly, Murphy (1995) reported that the responses of dry clipping yield from Ringer’s Restore (9-4-4) and two formulations of fish hydrolysate (2-1-0 and 2-1-1) were similar but the color and dry clipping yield in inorganic fertilizer was higher than those in organic slow-release ones. Considering the effect of soil conditioners on turf growth, a strong positive correlation between tissue N rate and clipping weight was obtained, indicating that high water-soluble N availability would have led to higher levels of N leaf tissue and thus would have increased clipping yields. Our data showed that the higher clipping production from urea and chlorothalonil had equivalent clipping dry weight and SMC and WC treatments had the lowest. This was most likely due to urea and chlorothalonil having higher N solubility, which resulted in higher nutrients available for the plant to absorb in both trials.

The root biomass data showed that soil conditioners did not improve root biomass at any of the depths of 0-5, 5-10 and 10+ cm in both greenhouse trials. For total root biomass, applications of soil conditioners provided equal or less total root development compared with the urea treatment. This reason could be the different solubility percent of N from each soil conditioner product. It is highly possible that the highest available N contained in fertilizers resulted in the best plant growth and thus they had the highest root biomass. Our results obtained from the response of soil conditioners on root biomass were supported by the previous literature. Solaiman and Hasan (2012) observed similar results with the root length of Brassica oleracea L. (cabbage), which did not differ with the application of organic manures and urea. Similarly, Gregoire (2004) found that methylene urea treatment had 53 % roots than composted manure (7-2-4) peat moss mixed with organic fertilizer. Prior research has also shown that root biomass production decreased with increasing N rate on creeping bentgrass and other turf species (Bowman, 2003; Watson, 2009; Elliot, 2003; Ericsson, 2012). We found that the half-rate urea-treated pots had less root biomass than those treated with the full rate of urea, suggesting that decreasing N rate led to a decrease in root biomass. Our results were in agreement with Xiao (2020) who found that turf receiving low N had the lowest root biomass and high N rate resulted in the highest root biomass production under three drought treatments after 60 days of fertilization. As discussed previously, the lack of response was associated with low N solubility. Accordingly, it is also assumed that a 100% sand rootzone might have led to a limited breakdown of WIN compared with a soil-based root zone as a sand-based root zone is very low in SOM and, consequently, microbial degradation (Charbonneau, 2008).

4.1.1 Field Studies

We hypothesized that soil conditioners would be able to reduce dollar spot severity through microbial activity. Our results demonstrated that dollar spot severity and AUDPC of dollar spot were not suppressed by soil conditioner applications when compared with either urea or chlorothalonil in both locations during the study period. Organic amendments and fertilizers have been demonstrated to reduce dollar spot severity through N availability and soil microbial activity (Davis and Dernoeden, 2002; Liu et al.1995; Nelson and Craft, 1992; Markland et al., 1969). We hypothesized that

the addition of N from soil conditioners would stimulate soil microbial diversity and antagonism; thereby suppressing the dollar spot disease. Although our objectives were mainly aimed at determining the suppressive capacity of soil conditioners in soil, we were unable to confirm this due to experimental error during the study that did not allow for the measurement of microbial activity. Therefore, we do not have data related to the question of whether or not these soil conditioners led to any detectable changes in microbial diversity or whether they promoted soil health pre- and post-inoculation. It is hard to draw a conclusion that there may be a relationship between disease suppression from soil conditioners and microbial activity as a result.

Based on our results, the lack of response of soil conditioners in the short term might be attributed to slow N release patterns of soil conditioners. N release of organic fertilizers greatly relies on microbial activity which is considered as an indicator of soil quality as this activity is responsible for the degradation of organic substrates and the release of plant nutrients (Gil-Sotres et al., 2005). The different N supply from organic fertilizers has been also demonstrated to suppress dollar spot disease through increased microbial activity (Gil-Sotres et al., 2005). Enhanced microbial activity may also result in an increased availability of nutrients, which may stimulate plants to recover from disease more rapidly (Boulter et al., 2000). It may not be valid to speculate about the effects of soil conditioners in response to disease suppression as mineralization rates and N forms of soil conditioners or their availability in soil over time were not investigated in this study. It has been reported that short term availability of organic materials depends on two factors: 1) N mineralization rate and 2) N content of organic substances (Serna and Pomares, 1993; Dosch and Gutser, 1996). Additionally, climate, soil texture and field conditions such as soil temperature, moisture level and microbial activity could play a critical role on decomposition of soil conditioners, which will influence disease control accordingly (Medina et al., 2010). More research on N release patterns is needed to determine the N availability as well as P and K concentration in plant as this will contribute to the understanding of factors that would play a significant role on decomposition of soil conditioners.

In addition, the addition of soil conditioners for 14 weeks revealed no effect on SOM in neither of the locations. Corominas (2011) reported an improvement in soil

organic matter with repeated biosolid and yard wastes top-dress applications. Another study by Davis and Dernoeden (2002) found that the increase in organic matter with organic fertilizers compared with urea and an untreated control. When we compare our study with previous research, the primary limitation would appear to be the short duration of the trial. Hence, SOM was not affected by soil conditioner treatments during the timeframe of our study. The long-term effects of organic fertilizers have been shown to increase SOM for turfgrass and other crops in trials that were conducted for a minimum of two years (Johnson et al., 2006; Egashira et al., 2003; Aggelides and Londra, 2000; Gutser, 2005).

Another indicator of soil health is aggregate stability. The data collected for soil aggregate stability at the GRS 1 location showed no significant relationship between soil conditioners and aggregate stability (Appendix Table C3.6). We did not collect data for GRS 2 as we assumed that with this site being a new facility, the aggregation was likely to be poor due to being sand.

Compost treatments have been shown to reduce the severity of a wide variety of diseases of turfgrass (Nelson and Boehm, 2002: Kaminski et al.,2004: Roulston, 2006). Beckley (2018) also reported that the effect of vermicompost biochar and biosolids reduced dollar spot disease compared with untreated control but did not differ from a synthetic fertilizer treatment. This finding was contradictory to our results because WC and SMC were the only treatments resulted in an elevated dollar spot severity compared with negative control, urea, at the end of the study in GRS 1 but not in GRS 2. Compost materials were proven to be highly suppressive to dollar spot when they were applied as preventative application on putting greens (Nelson and Craft, 1992). Boulter et al. (2001) compared a single compost application to an application every 3-weeks on dollar spot for a period of ten weeks after inoculation. While the single application was not effective to suppress dollar spot compared to the control, multiple applications of top-dressing reduced dollar spot on six of seven rating days. They also found that there was no difference among the different types of composts in either the single or multiple applications. In our study, although compost treatments (SMC and WC) were applied before inoculation like other soil conditioner applications to reduce dollar spot, there was no reduction in disease severity either from the beginning of dollar spot development (10 DAI) or until the end

of the study, likely due to the high disease pressure. One of the reasons for the ineffectiveness of the compost treatments could be explained by the very low percent of available nitrogen in these compost products. This is to say that the plots which received SMC and WC might have been deprived of nitrogen, causing poor vigor and chlorosis which could also have exacerbated dollar spot under high disease pressure throughout the study. Compost characteristic features can affect the disease suppression ability of the compost (Litterick et al., 2004; VanElsas and Postma, 2007). Physical and chemical characteristics of compost such as appearance, odor, moisture content, trace elements, nutrient composition, degree of decomposition and particle size are some of the indicators that determine the quality of compost (Garling and Boehm, 2000). Workman (2014) reported that monthly application of four compost treatments alone did not provide reduction in dollar spot disease in a one- year study compared with compost+boscalid and sulfur-coated urea + boscalid combinations. Previous studies have shown the fertilizer effects on dollar spot suppression, soil fertility and plant growth, with variable success most often in long term trials (Kelloway, 2012; Beckley, 2018; Landschoot and McNitt, 1997). The degree of effectiveness of composts to control disease greatly varies also depending on the duration of study, disease suppressive mechanism and environmental conditions (Boulter et al, 2001; Beckley, 2018; Liu et al, 1995; Hsiang and Tian, 2007; Davis and Dernoeden, 2002). Our studies were each conducted for one- season, and this may have not been sufficient to see significant differences. Furthermore, as pointed by Garling and Boehm (2000) the reason for the ineffectiveness of SMC and WC could have stemmed from differences within batch of same compost or among different sources of compost.

Turf color is believed to be the most important turf quality parameter (Glab et al. (2020). The current research showed that there was no enhancement in turf color from soil conditioner-treated plots before inoculation compared with the urea treatment in both locations. Likewise, turf color in soil conditioner-treated plots was either similar or lower than that obtained the urea-treated plots. In fact, none of the other treatments had acceptable (>6.0) turf color at the end of the study. These observations did not support the previous work conducted by Landschoot and McNitt,

(1997) or Davis and Dernoeden (2002), who found that improved turf color responses with decreasing dollar spot.

The NDVI is a quantitative measure of turfgrass green color and visual quality and is often used to determine N fertility treatment differences (Bell, 2004). Our study showed that none of the soil conditioner treatments resulted in higher NDVI values than urea and chlorothalonil in both locations. Before inoculation, turf at GRS 1 treated with soil conditioners was as healthy as those treated with urea and chlorothalonil. At GRS 2, on the other hand, only urea including plots (AWCT+urea and AWCT+urea+FH) showed similar NDVI values compared to urea and chlorothalonil. These varying results could be attributed to location factor which addresses site specific responses of canopy reflectance to soil conditioner applications. In addition, the results obtained from the preventative applications of soil conditioners at GRS 1 suggest that N mineralization rate of soil conditioners may be similar to those of synthetic fertilizer and chlorothalonil before the infection process, resulting in increased chlorophyl and photosynthesis that developed denser green turf canopy. Under infection process, soil conditioners failed to provide greener dense turf than urea and chlorothalonil at both locations. The healthiest turf was observed in chlorothalonil-treated plots on all evaluation dates at both locations, with the exception of 10 DAI at GRS 1. We did not observe any significant differences between any of the treatments on NDVI value at 10 DAI, indicating that soil conditioners yielded as healthy turf as chlorothalonil did when the disease severity was low in the beginning of the trial. However, these similar NDVI values in soil conditioners and chlorothalonil treatments across time did not last when the dollar spot became very severe throughout the season. All these findings observed in both locations indicate that not only did chlorothalonil promote plant growth but also it preserved discoloration from dollar spot.

Our study also aimed to evaluate the impact of rolling along with soil conditioners on dollar spot suppression. There was no interaction between the main effects of rolling treatment and soil conditioner treatment and there was no effect of the rolling treatment on dollar spot suppression in GRS 1. According to Horvath et al. (2009), no difference was observed in dollar spot severity on rolled and unrolled plots of creeping bentgrass when rolling was applied two or three times a week through a six-

week data collection. On the other hand, rolling influenced turf color and disease severity at GRS 2. The change in turf color in rolled plots appeared only at 50 DAI, indicating that rolled plots had significantly higher turf color than unrolled plots under high disease pressure. Likewise, disease severity in rolled plots was significantly lower than unrolled plots at 45 and 50 DAI. Giordano et al. (2012) found that rolling five times per week, whether in the early morning or in the afternoon, and either once or twice daily, significantly reduced dollar spot severity when compared with the control. Green et al. (2015) reported that rolling treatments applied five times weekly proved to be most efficacious, having the lowest percentage of dollar spot when compared with the control and the rolling treatments applied once and three times weekly. Nikolai et al. (2001) demonstrated that rolling at least three times per week not only increased green speeds, but also reduced dollar spot incidence in creeping bentgrass. Green et al. (2019) investigated the efficacy of sand topdressing and rolling on dollar spot severity in a mixed-sward creeping bentgrass and annual bluegrass fairway in a three-year research and reported that rolling treatment did not result in a consistent dollar spot suppression compared with sand topdressing. We hypothesized that rolling practice will also help to suppress dollar spot disease. In our study, although plots were rolled three times a week early in the morning for seven weeks, we did not observe any rolling effect on dollar spot reduction at GRS 1. This may have been due to the fact that our rolling treatments were initiated relatively late, after the plots were inoculated, and therefore after the point at which the disease had already developed. Therefore, late initiation of rolling practice likely led to no significant results. Our findings may suggest a recommendation for future research to garner adequate data through a longer period. That said, future studies should assess the different frequency of rolling along with a soil conditioner application under low to moderate dollar spot pressure for a longer period of time, both within a season and across multiple seasons.

Our results suggest that the effects of rolling on disease severity depend on location. For example, GRS 1 had well-established putting greens having a history of dollar spot whereas the second location (GRS 2) had newly seeded putting greens. It is possible that weather conditions affected the existing amount of inoculum which was built up in thatch in the previous years. Thus, this rapid disease development

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might have masked the effects of rolling and soil conditioner treatments at GRS 1. The rolling effect on disease severity at GRS 2, however, started to be noticeable on the last two rating days, and the effect on turf color was not observed until the last rating day. Both were likely due to the comparatively lower average temperature (15˚C) in September which resulted in lower dew volume on turf foliage compared with dew volume in July and August.

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5 Conclusion

This study aimed to investigate the effects of soil conditioners including fish emulsion, fish hydrolysate, spent mushroom compost and worm castings on dollar spot control on creeping bentgrass in golf courses putting greens. Their effects in a controlled environment setting and in the field were assessed. The practice of rolling, which is known to reduce the disease on golf course greens, was integrated into fertility program in the field studies. We hypothesized that dollar spot would be suppressed by soil conditioners as a result of improved plant nutrition and growth in a greenhouse study. The results of our study, however, did not support the hypothesis that soil conditioners would suppress dollar spot versus synthetic fertilizer in the greenhouse. None of the soil conditioners were effective in reducing dollar spot disease. Additionally, turf treated with soil conditioners did not exhibit improved turf color, root biomass, tissue N concentration and clipping dry weight compared with those that received inorganic fertilizer. Previous research indicated that an important factor in reducing dollar spot is available N to the plant (Lui et al., 1995; Landschoot and McNitt, 1997; Davis and Dernoeden, 2002). The tissue N concentration data collected in this study provided us with insight into some possible reasons why soil conditioners failed to show adequate efficacy in dollar spot inhibition.

In the light of these findings, we cannot recommend the use of soil conditioners tested in this study as an alternative method to turf managers to incorporate in their disease control program. However, more research is likely needed to determine the effects of soil conditioners over a longer period, since our study was only conducted over one season. Secondly, future research should be conducted for simultaneous greenhouse trials with more replicates with different experimental designs and should include a larger sample size to obtain more accurate data since the visual estimation of disease assessment methods are highly subjective. In our study, turf examination may have been influenced by factors such as eye fatigue, lighting and personal opinion, all of which could affect the disease assessment perception. In addition to this, having small experimental units might have allowed variation to enter our data, leading to poor visual estimation of disease assessment. Developing a research- based understanding of soil conditioners’ effect on dollar spot reduction will require

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taking possible confounding factors (e.g. drought stress) into account to obtain significant results.

The purpose of the field study was to investigate the effects of the combination of rolling and soil conditioner treatments in reducing dollar spot disease. We hypothesized that by increasing soil microbial activity and thereby soil health, disease severity would be reduced as a result of increased plant health and disease suppression. In this short-term field study, neither dollar spot severity nor turf color and NDVI were affected positively by soil conditioners in pre- and post-inoculation period in both locations. However, at GRS 1, all soil conditioner-treated plots provided turf color as green as chlorothalonil-treated plots prior to dollar spot inoculation. We also demonstrated that rolling had a significant effect on turf color and disease severity in one of our two field locations. Findings from this study also suggest that rolling can be used as an integral part of management of putting greens to reduce dollar spot disease. The potential for rolling in combination with soil conditioners over a longer period of time may be a subject of further research in order to investigate the long-term impacts of rolling with the applications of soil conditioners on disease suppression and turf color.

And interesting observation from our study was the negative effects of SMC and WC on disease severity and turf color. These results were likely due to the high percentage of insoluble N that was found in compost material compared with the other soil conditioners. It is worth mentioning that compost quality is also an important factor which has a potential to suppress disease (Noble and Coventry, 2005). Unfortunately, compost has highly variable characteristics with regard to availability of N depending on the source of material it contains and how it is composted (Mangan et al., 2013; Harrison, 2008). It is difficult to assume a consistent disease suppressive ability for most composts as they may not provide sufficient nourishment due to their nutrient-deficient content. It may also vary within different batches of the same compost. Therefore, the disease suppression effect of compost is largely variable and inconsistent (Hadar, 2011). Some researchers suggest that compost materials when used alone are not as effective as synthetic fertilizers to maintain turf visual color and quality. (Landschoot and Waddinton, 1987; Gardner, 2004). One strong conclusion that can be drawn from our research study is

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that available N from soil conditioners is of great importance when integrating them into management practices of putting green turf.

To the best of our knowledge, this is the first study testing SMC, WC, FE, FH and their combinations against dollar spot disease in both field and greenhouse trials. There is a growing desire for the use of organic fertilizers to avoid the use of fungicides in disease control due to environmental concerns. It is known that organic fertilizers can increase soil microbial biomass and yet this is often associated with increase in organic matter and soil fertility with repeated applications over time (Herenica et al, 2008; Diacono and Montemurro, 2010). The poor activity of tested soil conditioners against dollar spot limited the evidence required to advise turf managers to include these soil conditioners into their fertility programs. That said, these soil conditioners as combined in this study are not recommended for golf course fairway and putting greens in order to combat dollar spot. In addition, changes in composition of soil organic matter and microbial activity by organic fertilizers need a longer duration time in soils thus, golf course superintendents have continued to rely on inorganic fertilizers and pesticides for the control of dollar spot (Garling and Boehm, 2001). With the ultimate aim of reducing the use of fungicides, using soil conditioners with different N rates, implementing different application methods or including other management practices for putting green turf may be an alternative disease management approach for turf managers to minimize the dependency on fungicide usage.

This research clearly shows that further examination is needed to investigate the potential benefits of soil conditioners in managing dollar spot, particularly in the long run. Future research should aim to gain a better understanding of the suppressive capacity of soil conditioners on dollar spot disease and also to ascertain whether this capacity achieves such an effect by increasing soil microbial activity, soil aggregate stability and soil organic matter. As scant or no research exists concerning disease suppressing effects of combinations of the soil conditioners used in our study, there is a considerable potential for future work to further investigate their ability to manage dollar spot. The soil conditioner treatments in this study did not fully reflect the anticipated suppressive effects; however, we can reach the conclusion that further research with an extended scope and time would likely eliminate the limitations that

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occurred in the current study, ideally yielding solid evidence for disease suppressive properties of soil conditioners.

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APPENDICES

Appendix A. ANOVA tables for GH (greenhouse) study 1:

Disease Severity Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 243 63.06 <.0001 Day (D) 6 243 112.84 <.0001 SCxD 48 243 4.36 <.0001

Cov Parm Estimate Standard Error Ar (1) 0.3509 0.07121 Residual 0.2733 0.03139

Turf color Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 36 232.81 <.0001 Day (D) 4 144 33.86 <.0001 SCxD 32 144 8.85 <.0001

Cov Parm Estimate Standard Error Rep 2525.71 4691.89 Rep*S 35641 8910.61 Residual 1.0000 .

AUDPC Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 32 29.38 <.0001

Clippings Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 36 1.21 0.3193

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Root biomass Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 36 2.31 0.0412 Depth (d) 2 71 95.59 <.0001 SCxd 16 71 1.83 0.0438

Tissue N content Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 36 51.29 <.0001

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Appendix B. ANOVA tables for GH study 2:

Cov Parm Estimate Standard Error AR (1) 0.6490 0.04433 Residual 226.21 27.1472 Soil Conditioner (SC) 9 40 5.65 <.0001 Day (D) 6 240 40.0 <.0001 SCxD 54 240 1.47 0.0272

Cov Parm Estimate Standard Error CS 0.06579 0.02841 Residual 0.2839 0.03139

Turf color Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 9 40 46.46 <.0001 Day (D) 4 144 148.46 <.0001 SCxD 36 144 3.08 <.0001

Appendix Table B2. 3: Proc mixed analyses results of the effects of soil conditioner treatments on area under disease progress curve (AUDPC) on dollar spot in creeping bentgrass ‘Penn A- 4’maintained as fairway height of cut (6mm) in GH study 2, Guelph, ON in 2019

AUDPC Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 9 36 5.11 0.0002

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Clippings Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 9 40 1.13 0.3673

Root biomass Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 9 40 4.08 0.0009 Depth (d) 2 80 257.57 <.0001 SCxd 18 80 0.90 0.5802

Tissue N content Source of variation Num df Den df F value Pr > F Soil Conditioner (SC) 8 36 51.29 <.0001

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Appendix C. ANOVA tables for field study of GUELPH RESEARCH STATION 1 (Guelph Research Station):

Appendix Table C3. 1: Proc mixed variance analyses results of the effects of soil conditioner treatments on dollar spot severity in creeping bengtrass ‘Penn A-4’ putting greens at GUELPH RESEARCH STATION 1, Guelph, ON, in 2019

Cov Parm Estimate Standard Error Block 0.9145 0.9933 Block*Rolling 0 . CS 1.7688 1.1192 Residual 24.4915 1.9223

Disease Severity Source of variation Num df Den df F value Pr > F Rolling (R) 1 3 3.50 0.1582 Soil Conditioner (SC) 8 372 238.78 <.0001 RxSC 8 372 0.64 0.7475 Rolling x Day(D) 6 372 0.57 0.7547 SCxD 48 372 22.61 <.0001 SCxRxD 48 372 0.78 0.8506

Appendix Table C3. 2: Proc mixed variance analyses results of the effects of soil conditioner treatments on turf color in creeping bengtrass ‘Penn A-4’ color putting greens at GUELPH RESEARCH STATION 1 in Guelph, ON, in 2019

Cov Parm Estimate Standard Error Block 0.1750 0.1946 Block*Rolling 0.07388 0.09290 CS 0.09441 0.07580 Residual 1.5525 0.1339

Turf Color Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 0.00 0.9761 Soil Conditioner (SC) 8 317 29.15 <.0001 RxSC 8 317 0.95 0.4736 Rolling x Day(D) 5 317 1.66 0.1422 SCxD 40 317 2.02 0.0005 SCxRxD 40 317 0.80 0.7956

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Appendix Table C3. 3: Proc mixed variance analyses results of the effects of soil conditioner treatments on area under disease progress curve (AUDPC) in creeping bentgrass ‘Penn A-4’ at GUELPH RESEARCH STATION 1 putting greens, Guelph, ON in 2019

Cov Parm Estimate Standard Error Block 3640.91 6599.75 Block*Rolling 15882 16564 Residual 39312 8024.51

AUDPC Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 0.00 0.9687 Soil Conditioner (SC) 8 48 0.70 <.0001 RxSC 8 48 19.68 0.6905

Appendix Table C3. 4: Proc mixed variance analyses results of the effects of soil conditioner treatments on NDVI (Normalized Difference Vegetation Index) in creeping bentgrass ‘Penn A-4’ putting greens at GUELPH RESEARCH STATION 1 in Guelph, ON, in 2019

Cov Parm Estimate Standard Error Block 0.000149 0.000152 Block*Rolling 0.00018 0.000057 Residual 0.000757 0.000065 CS 0.000327 0.000093

NDVI Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 0.00 0.8748 Soil Conditioner (SC) 8 48 0.70 <.0001 RxSC 8 48 19.68 0.8029 Day (Day) 5 318 1503.12 <.0001 RxD 5 318 0.87 0.5032 SCxD 40 318 42.06 <.0001 RxSCxD 40 318 0.55 0.9889

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Appendix Table C3. 5: Proc mixed variance analyses of the effects of soil conditioner treatments on Soil Organic Matter (SOM) in creeping bentgrass ‘Penn A-4’ at GUELPH RESEARCH STATION 1 putting greens, Guelph, ON in 2019

Cov Parm Estimate Standard Error Block 0.01388 0.01453 Block*Rolling 0 . Scale 433.37 59.9627

% SOM Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 0.15 0.7100 Soil Conditioner (SC) 8 102 0.59 0.7801 RxSC 8 102 0.99 0.4463 Time (T) 1 102 0.18 0.6701 SCxT 8 102 0.58 0.7897 RxT 1 102 0.03 0.8708 RxSCXT 8 102 0.69 0.7006

Appendix Table C3. 6: Proc mixed variance analyses of the effects of soil conditioner treatments on Soil Aggregate Stability in creeping bentgrass ‘Penn A-4’ at GUELPH RESEARCH STATION 1 putting greens, Guelph, ON in 2019

Cov Parm Estimate Standard Error Block -1.6959 3.0860 Block*Rolling 4.2699 5.5469 Scale 22.4551 4.5836

% SOM Source of variation Num df Den df F value Pr > F Rolling (R) 1 3 0.89 0.4160 Soil Conditioner (SC) 8 48 1.59 0.1532 RxSC 8 48 1.22 0.3082

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Appendix D. ANOVA tables for field study of GUELPH RESEARCH STATION 2 :

Cov Parm Estimate Standard Error Block 8.6533 9.3570 Block*Rolling 2.0058 4.1738 CS 18.3098 5.6350 Residual 63.3838 4.9784

Disease Severity Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 11.97 0.0135 Soil Conditioner (SC) 8 372 26.54 <.0001 RxSC 8 372 1.92 0.0666 Rolling x Day(D) 6 372 9.55 <.0001 SCxD 48 372 8.68 <.0001 SCxRxD 48 372 0.79 0.8368

Cov Parm Estimate Standard Error Block 0.04190 0.05251 Block*Rolling 0.02804 0.03177 CS 0.04877 0.02024 Residual 0.2897 0.02494

Turf Color Source of variation Num df Den df F value Pr > F Rolling (R) 1 3 8.42 0.0272 Soil Conditioner (SC) 8 318 158.7 <.0001 RxSC 8 318 1.88 0.0622 Rolling x Day(D) 5 318 5.98 <.0001 SCxD 40 318 2.34 <.0001 SCxRxD 40 318 0.79 0.8219

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Cov Parm Estimate Standard Error Block 64522 209495 Block*Rolling 182173 188717 Residual 663675 135472

AUDPC Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 1.47 0.2709 Soil Conditioner (SC) 8 48 6.29 <.0001 RxSC 8 48 1.14 0.2644

Cov Parm Estimate Standard Error Block 0.000425 0.000376 Block*Rolling 6.324E-6 0.000058 Residual 0.000573 0.000056 CS 0.000444 0.000115

NDVI Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 10.09 0.0192 Soil Conditioner (SC) 8 261 182.94 <.0001 RxSC 8 261 0.98 0.4523 Day (D) 4 261 922.38 <.0001 RxD 4 261 11.02 <.0001 SCxD 32 261 54.28 <.0001 RxSCxD 32 261 0.74 0.8427

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Cov Parm Estimate Standard Error Block 0.002827 0.005517 Block*Rolling 0.003758 0.005159 Residual 0.04578 0.006441 % SOM Source of variation Num df Den df F value Pr > F Rolling (R) 1 6 0.64 0.4551 Soil Conditioner (SC) 8 101 1.59 0.1366 RxSC 8 101 1.09 0.3772 Time (T) 1 101 3.45 0.0660 SCxT 8 101 0.93 0.4948 RxT 1 101 3.63 0.0631 RxSCXT 8 101 1.24 0.2864

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