Long-term effect of integrated nutrient management in rice (Oryza sativa)–wheat (Triticum aestivum) cropping system

A field experiment was conducted on permanent manurial trial, initiated during the rainy (kharif) season 1985 at JNKVV, Jabalpur, to evaluate the long-term impact of fertilizer and manure and their integration on yield trends, production efficiency and soil-quality parameters and their inter-relationship with sustainable yield index (SYI) under rice (Oryza sativa L.)–wheat [Triticum aestivum (L.) emend. Fiori & Paol.] cropping sequence. The treatment 50% NPK + 50% N substituted through farmyard manure (FYM) to rice and 100% NPK to wheat provided the highest wheat-equivalent yield (WEY 8.01 t/ha) with net monetary returns ( 42.7 × 10³/ha) and recorded 430% higher system productivity over the control. The next best treatment was 50% NPK + 50% N substituted through green leaf manure (GLM) of sunhemp (Sesbania aculeata L.) to rice and 100% NPK to wheat gave higher WEY of 7.97 t/ha with net monetary returns (42.1 × 10³/ha). The treatment 50% NPK + 50% N substituted through farm yard manure (FYM) to rice and 100% NPK to wheat and 50% NPK + 50% N substituted through GLM to rice and 100% NPK to wheat also increased organic carbon (7.6 g and 7.9 g/kg), available N (282 and 292 kg/ha), P₂O₅ (15.4 and 17.2 kg/ha), K₂O (466 and 488 kg/ha), S (8.4 and 8.5 kg/ha) and Zn (0.43 and 0.45 kg/ha), sustained soil pH (7.49 and 7.48) and electrical conductivity (EC) (0.58 and 0.63 dS/m) and lowered the bulk density (1.27 and 1.27 g/cm³). In the treatment receiving 100–100% NPK through fertilizer to both rice and wheat crops, the total productivity was higher (7.72 t/ha). The higher sustainable yield index (0.83) was observed with 50% NPK + 50% N substituted through GLM to rice and 100% NPK through fertilizer to wheat crop. Maximum beneficial microorganisms, viz. fungi, bacteria, azotobacter, phosphorus solubilizing bacteria and actinomycetes were recorded with the integrated nutrient practices. Negative trend of net monetary returns was noted with control plot.