Correlation and Calibration Studies of Chemical Analysis in Soils and Plant Tissues for Nitrogen and Available Phosphorus

A large number of field trials have been conducted in central zone, northeast and northwest Mexico covering about 50 per cent of the agricultural land of the country for calibration of different chemical methods of soil and plant tissue analysis for evaluation of nitrogen status of soil and available soil phosphorus for predicting fertilizer response to corn, wheat and cotton. Ulrich's method of tissue test for nitrogen and Bray's P method for the available P in soils gave the highest correlation with percentage yield of crops in all the regions of Mexico. Limits and percentages of response probabilities for N and P in different regions of Mexico have also been worked out for cotton, wheat and corn.