Phosphate sorption approach for determining phosphorus requirements of wheat in calcareous soils |
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Authors: | K. S. Memon H. K. Puno R. L. Fox |
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Affiliation: | (1) Sind Agriculture University, Tandojam, Pakistan;(2) Department of Agronomy and Soil Science, University of Hawaii, 96822 Honolulu, HI, USA |
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Abstract: | Five field experiments involving P application rates from 0 to 66 kg P ha–1 were conducted on irrigated wheat at Tandojam, Pakistan. The soils belonged to two great soil groups, Torrifluvent and Camborthid. All soils were calcareous. Olsen-P contents ranged from 3.5 to 6.3 mg P kg–1. Phosphate sorption curves were developed for soils from control (no P) plots at each site. Concentrations of P in solution established by fertilization in the field as estimated from the sorption curves ranged from 0.008 to 0.16mg P L–1. Actual grain yields were converted to relative grain yields and plotted against corresponding concentrations of P in solution. Yield response to P application was obtained in each experiment. Control plot yields ranged from 57 to 89% of maximum yield of respective experiments. Phosphorus requirements of wheat were 0.032 mg L–1 for 95% yield as determined from a composite yield response curve. Predicted quantities of P required to attain 0.032 mg P L–1 ranged from 18 to 29 kg P ha–1. The results of the study suggest that the P sorption approach can be used as a rational basis for making P fertilizer recommendations for various soil-crop combinations. |
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Keywords: | Phosphate adsorption external P requirement wheat fertilizer requirements calcareous soils |
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