Diversification of traditional rice (Oryza sativa)-based cropping system for sustainable production in South Bihar alluvial plains

A field experiment was conducted during 1999–2000 to 2001–2002 at Sabour, Bhagalpur, to diversify traditional rice (Oryza sativa L.)-wheat (Triticum aestivum L. emend, Firoi & Paol.) cropping system. Among the rice-based-crop sequences tested, rice-potato (Solarium tuberosum L)–onion (Allium cepa L.) gave the highest rice-equivalent yield (26.94 tonnes/ha/year), net returns (Rs 65,573/ha) and production efficiency (81.6 kg/ha/day), followed by rice-potato-sunflower (Helianthus annuus L.) having corresponding values of 23.92 tonnes/ha/year, Rs 61,533/ha and 80.6 kg/ha/day. Rice yields after green-manuring or fodder crops were higher than those after gram crops including greengram (Phaseolus radiatus L.). The highest benefit: cost ratio of 1:47 was noted in rice-berseem (Trifolium alexandrinum L.)-maize (Zea mays L.) + cowpea [Vigna unguiculata (L) Walp.] both grown for fodder Rice-maize + greengram system had the highest land-use efficiency (96.8%). Rice-po-tato-onion required the highest energy inputs (69.90 x 10³ MJ/ha), resulting in the lowest energy-use efficiency (2.46), whereas rice-potato-sunflower produced the highest output energy (205.71 x 10³ MJ/ha). Green-manuring of Sesbania aculeata during summer improved organic carbon, available N, P₂O₅ and K₂O level of soil.