Long-term effects of integrated nutrient management on productivity and soil properties of rice (Oryza sativa)rice cropping system in coastal Odisha

Abstract

A long-term experiment was initiated in 198384 and continued for 31 years on integrated nutrient manage- ment (INM) in rice (Oryza sativa L.)rice cropping system at Bhubaneswar, Odisha. The study was conducted on sandy loams under irrigated conditions in a permanently laid out plot in randomized block design with 12 treat- ments and 4 replications. Application of 50% recommended dose of chemical fertilizers (RDF) coupled with 50% recommended N through green manuring of azolla or through FYM to rainy season (kharif) rice followed by supply of 100% RDF through chemical fertilizers to summer rice resulted in higher system yield of 9.07 and 8.75 t/ha/year respectively. This INM treatment was also most sustainable and improved the physico-chemical properties of the soil with respect to bulk density, soil organic carbon, available NPK, microbial biomass carbon and soil nutrient balance. Reduction in RDF by 100, 50 and 25% without supplementing any organic manure reduced system yield by about 52, 23 and 10%, respectively compared to RDF. Reduction in yield due to supplementation of 25 and 50% N through organic sources was to the tune of 10% during initial five years, and the yield gap between RDF and INM practices narrowed down with passage of time. Yield advantage due to supplementation of N through green manuring was noticed after 10 years, whereas that of FYM after 15 years. On the other hand, no yield ad- vantage was observed with supplementation of 25% N through paddy straw even after 31 years. Application of 50% RDF through fertilizers along with 50% recommended N through green manuring of azolla to rainy season (kharif) rice followed by supply of RDF through fertilizers to summer rice recorded the highest system gross re- turns 1,11,870 and net returns 65,644 with the highest benefit: cost ratio 2.42.