Relative efficacy of on-farm weeds as soil-amendment for managing dry root rot of clusterbean in an arid environment

Abstract

The effectiveness of certain on-farm weeds as soil amendments was ascertained against Macrophomina phaseolina, a soil-borne pathogen causing dry root rot of crops grown under rainfed conditions in arid regions. Populationchanges in M. phaseolina were determined in soils amended separately with residues (1%, w:w) of Aervapersica, Celosia argentea, Corchorus depressus, Euphorbia hirta, Heliotropium subulatum and Polycarpaea corymbosa, for a period of 90 days. Significant reductions by 90.4–100% in the population of M. phaseolina were achieved with allthe weed residues except P. corymbosa. Celosia and Euphorbia residues completely eradicated viable propagules of M. phaseolina. A strong increase (44–61%) in the population of antagonistic actinomycetes was also found in soil amended with Corchorus and Euphorbia. In field tests, soil amended (50 g m2) with Euphorbia, Aerva and Celosiaresidues significantly reduced dry root rot incidence on clusterbean and also reduced M. phaseolina propagules in thesoil. However, dry root rot incidence in Polycarpaea-amended soil (5.8–24.6%) was not significantly different fromthat in non-amended soil (4.3–25.3%) in both years of the experiment. P. corymbosa also increased the number ofpropagules of M. phaseolina in the soil. The results demonstrate that dry root rot of rainfed-cultivated annual cropsin arid land can be managed with certain weeds as a soil amendment.