Diversification of rice (Oryza sativa)wheat (Triticum aestivum) cropping system for sustainable production in south Bihar alluvial plains

A field experiment was conducted during 200910 to 201112 at Sabour, Bhagalpur, Bihar to diversify the ex- isting rice ( Oryza sativa L.)wheat [ Triticum aestivum (L.) emend. Fiori & Paol.] cropping system. Among the 12 rice-based cropping systems tested, scented ricepotato ( Solanum tuberosum L.) + radish ( Raphanus sativus L.)onion ( Allium cepa L.) + maize ( Zea mays L.) relay cropping gave the highest mean rice-equivalent yield (28.10 t/ha/year) and net returns ( 1,14,700/ha/year), followed by hybrid ricemaize + potatosorghum [ Sorghum bicolour (L.) Moench] + cowpea [ Vigna unguiculata (L.) Walp.] both grown for fodder (24.2 t/ha/year and 1,12,200/ha/year) and hybrid ricegarlic ( Allium sativum L.) + coriander ( Coriandrum sativum L.)maize for grain purpose + cowpea in-situ incorporation (22.60 t/ha/year and 1,11,600/ha/day). However, the benefit: cost ratio was the highest (1.39) in long-duration ricewheatmungbean [ Vigna radiata (L.) Wilczek] both sown by zero till, which was at par with scented ricewheat + fenugreek ( Trigonella foenum-graecum L.)mungbean grown for grain + residue incorporation (1.37). Scented ricepotato + radishonion + maize relay cropping required higher energy inputs (69.35 MJ 103/ha), whereas energy-use efficiency was the maximum (5.0) in ricemaize (ZT)clusterbean [ Cyamopsis tetragonoloba (L.) Taub.] (fodder). Hybrid ricemaize + potatosorghum + cowpea showed the high- est energy output (287.01 MJ 103/ha) and water-use efficiency (36.6 kg rice-equivalent yield/ha-mm). This crop- ping system removed the maximum quantity of N (448.4 kg/ha), P (130 kg/ha) and K (457.2 kg/ha) which resulted in maximum negative balance of phosphorus (32.8 kg/ha) and potassium (320.2 kg/ha). Potassium was negative in all the cropping systems, indicating that K was the most removable nutrient by the crops, which results in mining of soil K and thus calls for adequate fertilization.