Efficiency of Phosphatic fertilizers Differing in Water-Soluble Phosphorus in Rice

Nitrophosphate of 30% and nitrophosphate-superphosphates of 50 and 70% water-soluble phosphorus were evaluated under greenhouse conditions in comparison with superphosphate and dicalcium phosphate on Mangat loam and Gurdaspur sandy loam soils, low in Olsen's extractable—P, using rice as the test crop. Phosphatic fertilizers were applied at 15, 30, 45 and 60 kg P₂O₅/ha. Taking superphosphate as the standard source, the effectiveness of various sources of fertilizer P were enhanced with increase in the proportion of water-soluble phosphorus. Dicalcium phosphate (dihydrate) and nitrophosphate-superphosphate of 70 per cent water-solubility were almost equal in their efficiencies. Nitrophosphate of 30% water-solubility was the least effective source of fertilizer phosphorus.