Assessing P fertilizer requirements of soils with phosphorus sorption isotherms

Silva, J.A.; Fox, R.L.

Proceedings Planning and Organization Meeting, Fertilizer INPUTS Increasing Productivity under Tight Supplies Project: 100-105


Accession: 000296388

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Laboratory studies showed that sorption of phosphate from solution by 4 soils from North Carolina was related to soil mineralogy and rainfall as well as to previous P fertilization. Coatings of amorphous material appeared to control initial phosphate sorption in highly weathered soils. Data from a long-term trial in Hawaii revealed a steadily declining P sorption capacity with repeated P fertilizer application. In pot tests with soils of varying types and fertilizer history, pearl millet gave 92 to 99% of maximum yield when P concentration in the soil solution was adjusted to 0.2 ppm. Relationships were obtained between yield of five field-grown crops and P concentration in the soil solution.