Assessment of disease suppression in organic transitional cropping systems
type: CreativeWork
description: In order for agricultural land area to be certified for organic production, current USDA rules require that it goes through a three-year transition period prior to receiving certification in order to minimize the effects of previously applied synthetic pesticides or fertilizers and to improve “soil health”. Methods for enhancing soil health often include applications of organic matter to the soil. Adding organic matter to soils has been shown to lower the severity of soilborne/root-infecting diseases, a phenomenon known as organic matter mediated suppression. The aim of this study was to investigate the effect of adding organic matter, through cropping systems (pasture, cash grain, vegetable) and direct organic amendments (cover crops only, cover crops plus manure or compost), on soil suppressiveness during the certification transition period. Disease suppression of soybean pathogens, Rhizoctonia solani and Fusarium virguliforme was evaluated under the controlled environmental condition during transition, and field evaluations were conducted after transition. Naturally occurring diseases in the field were evaluated annually in order to compare the organic amendment effects. In addition, population levels of the Pseudomonadaceae were evaluated for suitability as a suppressiveness indicator. In greenhouse bioassays, disease levels were consistently higher on plants grown in autoclaved, infested field soil than in the same soil that was not sterilized, verifying the biological nature of the disease suppression studied. By using root morphology, along with severity ratings, my results provide evidence that adopting pasture as the transitional cropping system may promote organic matter mediated suppression of diseases caused by facultative saprophytes (e.g., F. virguliforme), while encouraging diseases caused by facultative parasites (e.g., R. solani). Over the three year transition period, there was an increase in soil suppressiveness based on greenhouse bioassay data. …
abstract: In order for agricultural land area to be certified for organic production, current USDA rules require that it goes through a three-year transition period prior to receiving certification in order to minimize the effects of previously applied synthetic pesticides or fertilizers and to improve “soil health”. Methods for enhancing soil health often include applications of organic matter to the soil. Adding organic matter to soils has been shown to lower the severity of soilborne/root-infecting diseases, a phenomenon known as organic matter mediated suppression. The aim of this study was to investigate the effect of adding organic matter, through cropping systems (pasture, cash grain, vegetable) and direct organic amendments (cover crops only, cover crops plus manure or compost), on soil suppressiveness during the certification transition period. Disease suppression of soybean pathogens, Rhizoctonia solani and Fusarium virguliforme was evaluated under the controlled environmental condition during transition, and field evaluations were conducted after transition. Naturally occurring diseases in the field were evaluated annually in order to compare the organic amendment effects. In addition, population levels of the Pseudomonadaceae were evaluated for suitability as a suppressiveness indicator. In greenhouse bioassays, disease levels were consistently higher on plants grown in autoclaved, infested field soil than in the same soil that was not sterilized, verifying the biological nature of the disease suppression studied. By using root morphology, along with severity ratings, my results provide evidence that adopting pasture as the transitional cropping system may promote organic matter mediated suppression of diseases caused by facultative saprophytes (e.g., F. virguliforme), while encouraging diseases caused by facultative parasites (e.g., R. solani). Over the three year transition period, there was an increase in soil suppressiveness based on greenhouse bioassay data. …
author: Marzano, Shin-Yi
language: en
keywords: disease suppressive soil, organic transition, Rhizoctonia solani, fusarium virguliforme, Pseudmonadaceae
date published: 2012-05-22T00:22:52Z
date modified: 2026-07-22T22:25:29Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/31031