Integrated nutrient management in a rice-rice cropping system

Abstract

An experiment entitled "Integrated nutrient management in a rice- rice cropping system" was condcuted at Cropping Systems Research Centre, Karamana during the second crop season of 1995-96, to study the effect of long term application of manures and fertilizers on the availability and uptake of nutrients and changes in the physico-chemical properties of the soil for sustained productivity. The experiment was laid out in randomized block design with twelve sets of treatments and four replications. The twelve sets of treatments incldued four treatments of different levels of recommended fertilizers, treatments of integration of chemical fertilizers with organic sources like farm yard manure, crop residues (rice straw) and green manure, along with one each of unfertilized control and farmers practice of manuring. Organic manure addition in different forms was found to have pronounced effect on various growth and yield attributing characters of rice when applied in combination with chemical fertilizers. When compared to other treatments, application of 25 or 50 per cent of recommended N through farm yard manure in kharif followed by 75 or 100 per cent of recommended NPK through chemical fertilizers in rabi, gave higher tiller number, root production, productive tiller number, thousand grain weight, grain yield, and straw yield. Integration of organic manures with inorganic fertilizers improved the N, P and K uptake by the plant at all growth stages and at harvest. Highest Nand K uptake were recorded when 50 per cent N, supplied through farm yard manure in kharif season. Highest P uptake was recorded when 25 per cent of N supplied through crop residue in kharif. In general the available N,P,K and organic carbon contents of the soil were slightly improved due to combined application of organic and inorganic sources of fertilizers. Application of farm yard manure to meet 50 per cent of N along with 100 per cent recommended dose of fertilizers recorded maximum available NPK and organic carbon Bulk density was lowest under treatment receiving 50 per cent recommended N through farm yard manure in kharif. Incorporation of paddy straw, to meet 25 per cent N along with chemical fertilizers enhanced water holding capacity and cation exchange capacity of the soil.