Evaluation of Some Phosphate Carriers for Their Efficiency in Vertic Ustochrept to Sustain High Productivity of Wheat and Rice

In a greenhouse experiment for two seasons three phosphate carriers (single superphosphate, diammonium phosphate and ammonium polyphosphate) were evaluated for direct and residual effects on wheat and rice, respectively and also for the effectiveness of APP to mobilize soil zinc in Vertic Ustochrept. Among the sources, SSPproved superior to DAP and APP in the production of wheat grain. Single superphosphate and APP recorded larger amount of P uptake by wheat grain compared to DAP. Grain and straw yields and P uptake by these components increased significantly up to 50 mg kg⁻¹ soil level. Among the P sources, APP and SSP maintained higher available P in soil than DAP at flowering and harvesting stages of wheat. The residual effect of P on the succeeding rice showed up to 100 mg kg⁻¹ soil irrespective of the sources of P. Zinc applied @ 5 mg P kg⁻¹ soil to wheat also significantly increased the grain and straw yields and P uptake by rice. The interaction effects revealed that 50 mg P kg⁻¹ soil as either SSP or APP gave higher yield of rice compared to DAP. Available P in soil at flowering stage in case of wheat and before sowing in case of rice bore significant positive relationship with respective grain and straw yields and P uptake.