Yield Potential, Nutrient Uptake, Metal Fractionation and Effect on Soil Properties under Integrative Use of Varied C:N Ratio Composts, Fly Ash and Inorganic Fertilizer Nitrogen in Rice Grown on Inceptisol

Field experiment was conducted to evaluate the effect of incorporating fly ash and spent mushroom composts of varied C-N ratio with and without fertilizer nitrogen on yield, trace metal content, nitrogen uptake, metal fractions and soil properties. Fertilizer nitrogen, fly ash and white button spent mushroom compost of narrow C-N ratio increased whereas oyster spent mushroom compost of wider C-N ratio decreased the paddy and straw yield. Cd and Ni content in paddy and straw, in the treatment comprising oyster spent mushroom compost did not vary significantly, however addition of fly ash or white button spent mushroom compost enhanced their content in paddy and straw. Zn content of paddy and straw in composts were higher as compared to fertilizer nitrogen, fly ash. Uptake of nitrogen by paddy and straw was higher under integrated nutrient treatments, however oyster spent mushroom compost resulted in initial nitrogen starvation, so reduction in nitrogen uptake. Compost mainly one with wider C- N ratio has shown more influence on adsorption of metals especially Zn. The exchangeable, organic matter bound and residual fractionation percentage were higher for Cd, Zn and Ni respectively in compost, especially one with wider C-N ratio.