Efficiency of nitrophosphates of varying water solubility with respect to their nitrogen (15N) and phosphorus (32P) utilisation

Nitrophosphates of different water soluble P superphosphate and super plus ammonium nitrate were compared by raising wheat as a test crop on alluvial soil of Delhi. Phosphorus was tagged with 32P and the ammonical and nitrate nitrogen was alternately tagged with 15N. With increasing the water-soluble P content in nitrophosphate, increasing amount of grain yield and higher uptake of total N and P were recorded. The percent phosphorus derived in the plant from the fertilizer and the percent phosphorus utilization was higher from the nitrophosphates of higher eater soluble P content. It was also higher under the application of superphosphate plus ammonium nitrate than superphosphate alone. A greater amount of ammonical nitrogen was utilized by the crop than nitrate form of nitrogen. (author)