Long-term effect of integrated nutrient management on yield sustainability and soil fertility of rice (Oryza sativa)–wheat (Triticum aestivum) cropping system

A long-term experiment was conducted on integrated nutrient management in rice (Oryza sativa)–wheat (Triticum aestivum L. emend. Fiori & Paol.) system at Jabalpur (Madhya Pradesh) since rainy (kharif) season 1987–88 to maintain the sustainable and high grain yields of this system without degradation of soil health under irrigated production system. The present paper deals with the studies conducted during the 2002–03 and 2003–04. Substituion of 50% N by green leaf manuring with sunnhemp (Crotalaria juncea L.) attained highest system productivity (33.12 kg grain/ha/day). While determining the sustainability yield index (SYI), the value was also maximum with 50% NPK + 50% N through green manuring with sunnhemp to rice, followed by 100% NPK to wheat. Maximum soil available nitrogen, phosphorus, potassium, sulphur and zinc, and minimum bulk density were noticed with substitution of 50% N by green manure. However, the pH value and EC were almost constant in all the treatments. Integrated use of 50% NPK and 50% N through green manuring of sunnhemp to rice followed by 100% NPK to wheat also fetched the maximum net monetary returns (Rs 34,403/ha/year) with the benefit: cost ratio 2.40.