University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2016 Anaerobic Soil Disinfestation: Meta-analysis and Optimization of Amendment Carbon Rate and C:N Ratio to Control Key Plant Pathogens and Weeds Utsala Shrestha University of Tennessee, Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Horticulture Commons, Plant Pathology Commons, and the Weed Science Commons Recommended Citation Shrestha, Utsala, "Anaerobic Soil Disinfestation: Meta-analysis and Optimization of Amendment Carbon Rate and C:N Ratio to Control Key Plant Pathogens and Weeds. " PhD diss., University of Tennessee, 2016. https://trace.tennessee.edu/utk_graddiss/3963 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Utsala Shrestha entitled "Anaerobic Soil Disinfestation: Meta-analysis and Optimization of Amendment Carbon Rate and C:N Ratio to Control Key Plant Pathogens and Weeds." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Plants, Soils, and Insects. David M. Butler, Major Professor We have read this dissertation and recommend its acceptance: Bonnie H. Ownley, Annette L. Wszelaki, Arnold M. Saxton Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Anaerobic Soil Disinfestation: Meta-analysis and Optimization of Amendment Carbon Rate and C:N Ratio to Control Key Plant Pathogens and Weeds A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Utsala Shrestha August 2016 Copyright © 2016 by Utsala Shrestha All rights reserved. ii DEDICATION In the memory of Sheela Shrestha iii ACKNOWLEDGEMENTS I would like to acknowledge all those individuals who helped me directly or indirectly during this dissertation preparation. It is my great pleasure to express my deep sense of gratitude and sincere appreciation to Dr. David M. Butler, for his valuable guidance and constant encouragement from the beginning to the end of my doctorate degree. He always made time for my works and me, and listen to me patiently. He is a cheerful and gem of person. I equally acknowledge and express my sincere gratitude to Dr. Bonnie H. Ownley for her constant support and suggestions during my entire doctoral study. She is one of great mentor in both life and study, and her work inspires me to follow her path. I am also deeply grateful to Dr. Arnold M. Saxton for his guidance in statistics. He has a pleasant personality and I will always remember his nice smile. I would also like to thank Dr. Annette L. Wszelaki for her constructive comments and helpful suggestions for the completion of this study. I am so glad to have them all in my Advisory Committee. I equally express my heartfelt thanks to Dr. Robert M. Auge for support and cooperation to write a meta-analysis chapter/article. This dissertation would have not been possible without assistance from the members of Dr. Butler’s lab: Sarah E. Inwood, Heather Toler, Hanna, Sarah, Will, Justin, Cody, Grant, Geoferry, Zach, and Bronson, members of Dr. Ownley’s lab: Mary Dee, Alex, Sara and staff members of UT Plateau Research and Education Center, Crossville: John (Walt) Hitch and Ann Moore. I am also thankful to Dr. Erin Rosskopf and Jason Hong for their support and suggestions. It is the matter of my immense pleasure to express my deep gratitude and heartfelt respect to my all-family members (Shrestha and Piya) and friends for their affection, inspirations, and support to precede my academic carrier. Last but not the least, thanks to my beloved husband Sarbottam Piya for his constant support during my dissertation preparation, his constructive feedback, and, support in every step of the way. iv ABSTRACT Anaerobic soil disinfestation (ASD) is an environmentally friendly and cost effective pre-plant soil treatment technique that allows effective control of soilborne pests by creating anaerobic conditions, particularly for specialty and organic crop production under diverse environmental conditions. In spite of being a proven technique, ASD has to be optimized to fit into local production systems with specific pathogen pressure using locally available amendments for successful implementation on a commercial scale. Our meta-analysis study on soilborne pathogens, plant parasitic nematodes, and weeds validated that ASD is an effective approach to control various soilborne pathogens. This study aims to optimize the carbon rate and carbon to nitrogen ratio (C:N) of two ASD amendments namely, dry molasses and wheat bran to suppress Fusarium oxysporum, Sclerotium rolfsii and Cyperus esculentus tubers for a moderate soil temperature regime. Evaluation of survivability of recovered tubers, Fusarium oxysporum and Sclerotium rolfsii inocula corroborated with the finding of our meta-analysis that ASD effectively promotes tuber and pathogen propagule mortality. Evaluation of various carbon amendment rates maintained at a C:N ratio of 30:1 showed that 4 milligrams of carbon per gram of soil was the most effective to induce sclerotial mortality and parasitism. We found that maintaining an amendment C:N ratio within the range of 20:1 to 30:1, with carbon rate at 4 milligrams of carbon per gram of soil, is effective in generating favorable anaerobic conditions resulting in higher pathogen suppression and enhancement of beneficial mycoparasites. Keywords: Anaerobic / biological soil disinfestation, beneficial microorganisms, Fusarium oxysporum, meta-analysis, mycoparasitism, Sclerotium rolfsii, soilborne pathogens, Trichoderma, yellow nutsedge v TABLE OF CONTENTS Introduction .............................................................................................................. 1 Appendix ..................................................................................................................................... 4 Chapter 1 A meta-analysis of the impact of anaerobic soil disinfestation on pest suppression and yield of horticultural crops ............................................ 5 Abstract ....................................................................................................................................... 7 1. Introduction ............................................................................................................................. 8 2. Materials and Methods .......................................................................................................... 10 2.1 Data Collection ............................................................................................................... 10 2.2 Moderator variables ....................................................................................................... 11 2.3 Effect size and meta-analysis .......................................................................................... 12 2.4 Publication bias and sensitivity analysis ........................................................................ 13 3. Results ................................................................................................................................... 14 3.1 Measure of efficacy ......................................................................................................... 16 3.2 Pathogens ........................................................................................................................ 17 3.2.1 Experimental conditions for pathogen studies ............................................................. 18 3.2.2 Amendment effect on pathogen suppression ................................................................ 18 3.3 Nematode suppression .................................................................................................... 19 3.4 Weed suppression............................................................................................................ 20 3.5 Yield ................................................................................................................................ 21 4. Discussion ............................................................................................................................. 22 4.1 Is ASD effective for pathogen suppression? ................................................................... 22 4.2 Conditions favoring ASD effectiveness on pathogen suppression .................................. 23 4.3 Contribution of ASD amendments to pathogen suppression .......................................... 25 4.5 ASD effect on nematode suppression .............................................................................. 26 4.6 ASD effect on weed suppression ..................................................................................... 27 4.7 ASD effect on crop yield ................................................................................................. 27 5. Conclusion ...........................................................................................................................