Determination of Phosphorus Fertilizer Dose for Rice Using Mitscherlich-Bray Equation

Soil fertility maps in India showed that more than 90% of Indian soils are deficient in available phosphorus (P) although built-up is also reported in some areas. In this study, the modified Mitscherlich–Bray (MB) response equation was used to generate P fertilizer rates for aerobic rice by supplying with graded dose of P fertilizers. Three strip of different P gradient was created. Response of aerobic rice to added P suggested that crop showed a diminishing return with increasing dose of P. The data fitted to Mitscherlich-Bray (MB) equation showed that the theoretical maximum yield was estimated to be 60.847 (±0.394) q ha-1, the value of c related to the efficiency of the soil and fertilizer P is 0.084 (±0.008) and the R2 calculated using the uncorrected sums of squares is 0.988 that the MB equation is quite reliable. The estimated P rates for rice based on soil test values, price of fertilizers/price of crop ratio, and marginal rate of return would range from 57 – 68 kg ha-1 and this is much higher than the general recommended dose of 22 kg ha-1.