ECONOMIC OPTIMA OF PHOSPHORUS IN YELLOW AND BLACK SOYBEAN (GLYCINE-MAX)

An experiment was conducted during the rainy seasons of 1986 and 1987 to assess the relationship between phosphorus level of yellow ('JS 72- 44') and black ('JS 76-188') soybean [Glycine max (L.) Merr.]. Soybean responded well to P application and the optimum level was 88.09 and 9 4.47 kg/ha, yielding 1,760.33 and 1,870.79 kg/ha in yellow and black s oybean respectively. However, the yield maximization of yellow and bla ck soybean required 94.93 and 104.82 kg P2O5/ha, giving yield 1,764.03 and 1,877.46 kg/ha respectively. The net profit obtained was Rs 17.76 and 15.40/Re invested on optimum P2O5 level of fertilization. The eco nomic optima at various price ratios showed a decrease in optimum leve l with the increase in ratio.