Phosphate sorption by soils as a measure of the phosphate requirement for pasture growth

Abstract

Development of a laboratory method for predicting the phosphate requirements of pasture plants, in pounds phosphorus per acre, is described. Measurement of the phosphate sorption by soil at a standard equilibrium concentration was used.

Predictions made by using this method in the following year on different soils accounted for over 85% of the variability in phosphate requirement.

A good correlation between phosphate sorbed and phosphate required was found. The relationship was linear over the range 0–500 p.p.m. of sorbed P. While different sampling depths, equilibrium concentrations, and degree of soil mixing affected the relationship, it remained linear and the correlation coefficients close to 0.9.