Development of suppressiveness to diseases caused by Rhizoctonia solani in soils amended with composted and noncomposted manure

Fresh and composted dairy manure were compared along with other amendments in the greenhouse and in field microplots for their effects on induction of suppression to plant diseases caused by Rhizoctonia solani. Damping-off of radish induced by R. solani was least severe for seedlings planted in the greenhouse in soil media amended with urea and straw, more severe with manure or compost, and most severe after urea treatment. Radish damping-off was less severe at all inoculum density levels in the urea with straw treatment than in the other amendment treatments. At very high infestation levels (20 and 30 cfu/g R. solani), disease severity did not differ among the least effective amendments