Integrated nutrient management in rice (Oryza sativa) - rice - cowpea (Vigna unguiculata) sequence under humid tropical Andaman Islands

A field experiment was conducted during 1993-94, 1994-95 and 1995-96 to stu dy the effects of integrated nutrient management in a rice (Oryza sativa) - rice - cowpea [Vigna unguiculata (L.) Warp.] sequence on crop productivity , soil fertility and economics. Combined use of 50% NPK + 50% poultry manur e significantly increased the grain yield of first rice crop (74%) and seco nd rice crop (79.8%) over the control. The effect of 50% NPK + 50% FYM and NPK dose alone was also comparable. Application of FYM and poultry manure a lone or combined with 50% NPK had significant residual effect on the pod yi eld of cowpea. The pH and EC values did not change significantly. The highe st increase in soil organic carbon (0.68%) was obtained from FYM applicatio n over initial value of 0.45%. The available N increased to 276 kg/ha under 50% NPK + 50% poultry manure treatment over initial value of 220 kg/ha. Th e application of poultry manure alone increased the available P (15 kg) and K (121 kg) over initial status, 11 and 112 kg/ha:respectively. Highest net returns (Rs 23,083/ha) and benefit : cost ratio (1.67) were obtained from application of 50% NPK+ 50% poultry manure.