Efficiency of nitric phosphates and Mussoorie rock phosphate in three cycles of clusterbean–wheat and groundnut–wheat rotations

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Abstract
SUMMARY: Nitric phosphates containing 80, 50 and 30% water-soluble phosphorus, and Mussoorie rock phosphate, alone or with Amjhore pyrites, farmyard manure or straw, were compared relative to concentrated superphosphate for each of three cycles of a clusterbean–wheat and a groundnut–wheat rotation. Both the field experiments were made on alkaline P-deficient Samana sands. All phosphatic fertilizers were applied to each crop at the rate of 10, 20 and 30 kg P/ha. Dry forage of clusterbean, groundnut pods and grain yield of wheat were measured. The model of concurrent straight line response was employed to calculate availability coefficient ratios which express the relative effectiveness of the different phosphatic fertilizers.Nitric phosphate containing 80 % water-soluble phosphorus and concentrated superphosphate were almost equal in their effectiveness in both 3-year rotational studies of clusterbean–wheat and groundnut–wheat. The relative efficiency of the nitric phosphates increased with the amount of water-soluble phosphorus they contained. Mussoorie rock phosphate was the least effective source of fertilizer phosphorus, although its efficiency is considerably higher for the legume clusterbean and for groundnut than for the cereal wheat. The efficiency of Mussoorie rock phosphate increased when it was mixed with the soil together with Amjhore pyrites, farmyard manure and straw respectively. These materials were more effective for clusterbean and groundnut than for wheat.