ASSESSMENT OF SUITABILITY OF SOIL TEST METHOD FOR AVAILABLE-P ESTIMATION TO SOYBEAN GROWN IN VERTISOLS.

Field and pot experiments were conducted at College of Agriculture, Indore to asses suitable method for P availability in relation to soybean rhizosphere point of view. The yield of soybean seed and uptake of phosphorus under medium phosphorus status Vertisols found non-significant to applied P levels. The better correlation coefficient was found for Bray 2 (r2=0.829) than Olsen (r2=0.490) method therefore, Bray 2 soil test method was adjusted to be the better method for assessing the phosphorus status in Vertisols. Phosphorus can be solublized from the Ca-P inorganic phosphorus fraction by acidification of rhizosphere, as a result of excretion of organic acids and H+ from roots. Among the different inorganic P fractions of Vertisol Ca-P was the most important P fraction for P nutrition of soybean. [ABSTRACT FROM AUTHOR]