STUDIES ON THE DECOMPOSITION OF NONCONVENTIONAL ORGANIC WASTES IN SOIL

An experiment was conducted to investigate the effect of four non-conventional organic wastes viz., Justicea simplex, Jatropa gossypifolia, Ipomoea cornea and Cestrum diurnum at a concentration of 0.5% (on soil weight basis) on the rate of decomposition and the microbial dynamics in soil. Justicea simplex liberated the maximum amount of carbon dioxide from soil on the 2nd day. Other organic additives liberated the highest amount of carbon dioxide on the 3rd day. During 84 days of decomposition, the cumulative amount of CO2. evolution was in the order: Justicea simplex >Cestrum diurnum> Ipomoea cornea> Jatropa gossypifolia. Different organic residues exerted differential stimulation of microbial proliferation in the soil. Jatropa gossypifolia gave rise to the maximum number of total bacteria in soil. Cestrum diurnum and Jatropa gossypifolia induced a similar effect on the actinomycete population. The augmentation of fungal colonies in the presence of different wastes was similar. Cestrum diurnum harboured the maximum number of non-symbiotic nitrogen-fixing bacteria and phosphate-solubilizing microorganisms. Justicea simplex and Jatropa gossypifolia were superior to Cestrum diurnum and Ipomoea cornea with respect to nitrogen fixation. None of the organic additives stimulated the phosphate-solubilizing capacity of the soil.