Effect of organic amendments on Rhizoctonia and accompanying microflora in soil.

Abstract

The effect of oat straw, green bean plants, and cellulose on the infection index and saprophytic activity of Rhizoctonia, and the effect of chitin, N-supplemented oat straw, and green cotton plants on the infection index, saprophytic activity, and soil microflora was tested. A modified method for counting Rhizoctonia-antagonistic bacteria, actinomycetes, and fungi was developed. A relationship between efficiency of the amendments in decreasing infection index and in suppressing the saprophytic activity of Rhizoctonia was observed at the end of the experimental period. Decrease in infection index and saprophytic activity was accompanied by increase in counts of general and antagonistic soil microorganisms. This increase was especially pronounced in chitin-amended soil. The possible mechanism of the biological control of Rhizoctonia by chitin is discussed.