The calibration of soil tests for fertilizer requirements

Abstract

The predictability, from soil test measurements, of principal components of yield responses to superphosphate was examined using data previously published (by J. D. Colwell). On assessing the overall predictions of principal components by the adjusted coefficient of determination, approximately 45% of the variability was so accounted for. Since this is approximately 9% greater than that accountable for by Colwell's procedure, it is suggested that a calibration procedure for soil tests (to yield fertilizer requirements) could be based on such prediction equations, and is worth further consideration.