Quantity Factors of Soil Phosphorus and Utilization of Fertilizer Phosphorus by Barley

Experiments were conducted in pots using laterite soil from Kerala and red soil from Goa with a view to study the relationship between per cent phosphorus saturation of the maxima (obtained from Langmuir adsorption isotherm or P sorption based on the method of Waugh and Fitts) and dry matter yield, total uptake of phosphorus, per cent phosphorus derived from fertilizer (% Pdff) and utilization of fertilizer phosphorus by barley. Application of phosphorus based on the percentage saturation of the maxima determined from the P sorption curves according to Waugh and Fitts was found to be a better index than that based on the Langmuir adsorption isotherm. In the red soil optimum yield of barley could be obtained with 20 per cent saturation of the maxima based on either of the methods although the yield was higher with P application based on Waugh and Fitts method while yield increase up to 80 per cent saturation was observed in the laterite soil.