Comparative Study of Four Techniques for the Labile Phosphorus Extraction and Critical Level for Corn Growth in Vertisols

In this research, the correlation and calibr ation of four extraction techniques for available phosphorus were studied: Soltanpour and Schwab, North Carolina, Olsen and Bray P 1 in six soils classified as Vertisols of the municipalities of Jiquilpan, Venustiano Carranza, Villamar, and Pajacuaran in th e Cienega de Chapala, Michoacan, Mexico. The aim of this work was to select an extraction technique for available phosphorus that evaluates the availability of this nutrient, and critical level for corn H - 303 variety phosphoric fertilization. A completely random design with four levels of phosphorus (00, 300, 600, and 1200 mg kg - 1 of soil) and four replicates was used. The dry matter yield, relative yield, and phosphorus uptake for corn plants were evaluated. The phosphorus critical levels by four analytic techniques using the graphic and mathematical procedures were determined. The phosphorous critical level by Olsen technique was 38 mg kg - 1 of soil, 38 mg kg - 1 of soil by Bray P 1 technique, 6 mg kg - 1 of soil by Soltanpour and Schwab technique, and 270 mg kg - 1 of soil by North Carolina technique. The best extraction techniques to determine available phosphorus were the Olsen and Bray P 1 techniques, with critical levels of 43 and 56.2 mg kg - 1 of soil, respectively.