POPULATION-CHANGES OF MACROPHOMINA-PHASEOLINA AND FUSARIUM-OXYSPORUM F SP CUMINI IN OIL-CAKE AND CROP RESIDUE-AMENDED SANDY SOILS

Population changes of Macrophomina phaseolina and Fusarium oxysporum f . sp. cumini were followed in a sandy soil amended with mustard and ca stor cakes or nitrogen-enriched pearl millet residue, singly or in com bined form. Populations of both the pathogens were reduced by 100% in the mustard-cake-amended soil within a period of 30 days after additio n. Amendment with nitrogen-enriched pearl millet residue significantly reduced the population of M. phaseolina within 45 days, but not that of F. oxysporum. However, incorporation of pearl millet residue in bot h types of cakes delayed the rate of reduction. The induced suppressiv eness in the cake-amended soil was associated with a substantial incre ase in the population of antagonistic actinomycetes. These results sug gest that amendment of soil with mustard cake in fields infested with M. phaseolina and F. oxysporum f. sp. cumini may reduce yield loss cau sed by dry root rot of guar (Cyamopsis tetragonoloba (L.) Taub.) and w ilt of cumin (Cuminum cyminum L.).