Doctoral Dissertations

Date of Award

8-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plants, Soils, and Insects

Major Professor

David M. Butler

Committee Members

Bonnie H. Ownley, Annette L. Wszelaki, Arnold M. Saxton

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.

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