Potential of organic soil amendments to control soil borne pathogens

Abstract: Soil suppressiveness against plant pathogens is a promising strategy to control diseases and crop losses. In the current study, a broad screening with 24 different organic amendments was performed to evaluate their ability to enhance disease suppressiveness of soil. Pot experiments with Pythium ultimum in cress and Rhizoctonia solani AG2-2IIIB in sugar beet were used as model systems. Pythium and Rhizoctonia disease suppression of the soil were significantly stimulated by respectively 7 and 4 out of 24 tested organic products compared to the nitrogen fertilized control. A lower C/N ratio of the products was, in general, a better indicator for suppressiveness than the respiration rate. Disease suppression against Pythium correlated significantly with potentially mineralizable nitrogen (PMN) in soil.