Grain production of wheat (Triticum aestivum), and nitrogen and phosphorus balance sheet in soil under sorghum (Sorghum bicolor) + cowpea (Vigna unguiculata)-wheat crop sequence

A 2-year (1995–96 and 1996–97) field experiment showed that grain and straw yields of wheat (Triticum aestivum L. emend. Fiori & Paol.) were maximum when grown after sorghum [Sorghum bicolor (L.) Moench] + cowpea [Vigna unguiculata (L.) Walp.] (F), followed by cowpea grain (SI) and these were found to be significantly higher than after sole crop of sorghum (F.) Phosphorus applied to previous rainy-season crops up to 30 kg/ha and direct applied N to wheat up to 75 kg/ha helped in increasing the grain and straw yields of wheat in both the years. The nitrogen, phosphorus and organic carbon (%) of soil improved owing to legume introduction in the cropping systems. The net returns and benefit: cost ratio from sorghum + cowpea (F)-wheat sequence were maximum, while sorghum (F)-wheat sequence gave least net returns.