Comparative Efficiency of Different Complex Phosphatic Fertilizers

The results of three years (1970–73) experiments to evaluate the comparative efficiency of various phosphatic fertilizers as diammonium phosphate, urea ammonium phosphate, Suphala (30% WSP), nitrophosphate (50% WSP) and superphosphate on maize and wheat revealed that in case of wheat the response to P source was directly related to the water soluble P content in the fertilizer material. On an average, wholly water soluble P sources proved equally effective and gave significantly higher yield to the extent of 13.8 to 22.5 per cent and 8.9 to 17.2 per cent over Suphala (30% WSP) and nitrophosphate (50% WSP), respectively. In maize, Suphala and nitrophosphate, the partially water soluble P sources were as effective as diammonium phosphate, urea ammonium phosphate and superphosphate, i.e., the wholly water soluble P sources. The P yields of wheat and maize indicated luxury consumption of P by maize from wholly water soluble P sources. All the phosphatic fertilizers gave residual effect. However, diammonium phosphate in maize fodder and superphosphate in wheat gave better residual effect than other sources. The correlation between soil test for P and the yield of succeeding crops was significant.