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 tradi- tional rice (Oryza sativa L.)-wheat (Triticum aestivum L. emend. Firoi & Paol.) cropping system. Among the rice- based-crop sequences tested, rice-potato (Solanum tuberosum L.)-onion (Allium cepa L.) gave the highest rice-equivalent yield (26.94 tonneslhalyear), net returns (Rs 65,573lha) and production efficiency (81.6 kglhal day), followed by rice-potato-sunflower (Helianthus annuus L.) having corresponding values of 23.92 tonnesl halyear, R s 61,5331ha and 80.6 kglhalday. Rice yields after green-manuring or fodder crops were higher than those after grain crops including greengram (Phaseolus radiatus L.). The highest benefit : cost ratio of 1:47 was noted in rice-berseem (Trfolium 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 lo3 MJIha), resulting in the lowest energy-use efficiency (2.46), whereas rice-potato-sunflower produced the highest output energy (205.71 x lo3 MJIha). Green-manur- ing of Sesbania aculeata during summer improved organic carbon, available N, P20, and K 2 0 level of soil.