Suppression of soil-borne pathogens in container media amended with on-farm composted agro-bioenergy wastes and residues under glasshouse condition

Abstract

The aim of this work was to assess the potential suppression of three on-farm green composts for controlling seven soil-borne pathogens in container media under greenhouse condition. Suppression of Pythium irregulare and Rhizoctonia solani damping-off of cucumber and bean, Phytophthora cinnamomi and Sclerotinia minor root rot of azalea and lettuce, and Fusarium oxysporum wilt of melon, tomato, and basil was studied on artificially inoculated seedlings. Three feedstocks of bioenergy wastes and agricultural residues were selected, on-farm composted, characterized, and tested for their suppressive properties by in vitro and in vivo experiments in comparison with one commercial compost from municipal solid biowaste. The composts showed differences in the suppressive properties when mixed with sterile peat at dosage of 35%. All green composts meanly suppressed P. irregulare damping-off of cucumber of 80%, R. solani damping-off of bean of 75%, P. cinnamomi root rot of azalea of 65%, and Fusarium wilt of up to 25%. The reference compost suppressed F. oxysporum wilt of melon, tomato, and basil from 60 to 70% and Pythium, Rhizoctonia, and Phytophthora diseases up to 30%. All composts suppressed S. minor root rot of lettuce of 35%. Suppression of Pythium damping-off and Phytophthora root rot was related to the sum of the bioactivities of the fungi and bacteria of compost. Suppression of Rhizoctonia damping-off and F. oxysporum wilt was associated with the specific bioactivity of a restricted number of fungi (Trichoderma, Aspergillus) and bacteria (Pseudomonas, actinomycetes) species. Suppression of Sclerotinia root rot was not related to any one variable of composts.