Phosphate Dynamics in Vertisols of Different Parent Materials

Transformation of added phosphorus into distinct fractions under incubation of a few Vcrtisol pedons of different parentage (viz. grey shale, basalt, granitic-granodiorite, granodiorite, and limestone) was studied. Applied phosphate transformed mostly into Ca-P followed by Fe-AI-P and carbonate-sorbed-P fractions and in general increased with increasing rates of phosphorus application in all the pedons irrespective of their parentage. Besides these fractions occluded-P in pedons derived from grey shale, granodiorite and limestone showed improvement compared to their respective initial soil occluded-P fraction values. Amongst the pedons, maximum Ca-P fraction i.e. 370 mg kg⁻¹ was observed in the Ap horizon of pedon derived from granodiorite parent material. Parent material apparently did not seem to have much influence in modifying the soils' ability to differentially enrich the added phosphorus into different fractions.