Influence of soil texture on survival and saprophytic activity of Rhizoctonia solani in soils.

Survival of Rhizoctonia solani in precolonized tablebeet seed was greater in a light-textured sandy loam (SL 1) than in a heavy-textured silty clay loam (SiCL). Reduction in survival as well as competitive saprophytic activity of the pathogen resulted when clays (kaolinite and montmorillonite) were added to SL to prepare soils of heavier texture. Survival and activity of R. solani, however, were not increased when sand was added to SiCL (suppressive to R. solani survival) to make this soil lighter in texture. In natural soils of different textures, activity of R. solani was maintained longer in two light-textured sandy loam soils than in a light-textured loamy sand or loam. During investigation of soil chemical and biological influences on R. solani survival, high K2O content in soil was significantly correlated with low saprophytic activity of the pathogen. In all instances where soil microbial activity as determined by a dehydrogenase assay was high, low saprophytic activity was found. Since high microbial activity or K2O content in soil were not associated with any particular soil type, biological or chemical factors may be more important than soil texture in influencing survival and activity of R. solani in soil.