Variation and Distribution of Phosphorus Fractions, their Relationship with Soil Properties in Vertisols and Aridisols of India

Abstract

One hundred eighty soil samples were collected from Vertisols and Aridisols to investigate status and depth distribution of phosphorus (P) pools and their relation to soil characteristics. Majority of the soils was clayey soil texture for Vertisols, while sandy for Aridisols, calcareous in reaction and medium to high in cation exchange capacity due to presence of illitic and smectite type of clay minerals. In both the orders, the amount of available-P, aluminium P (Al-P), Organic-P (Org-P) and total-P decreased with increase in soil depth, whereas calcium P (Ca-P) was found to be higher in lower horizons. Calcium-P was the most predominant P fraction in both the orders and contributes more than 21% of total P followed by organic P (>16%). Exchangeable Ca (Ex-Ca) and soil pH influenced distribution of soil P into different forms and its availability while salinity had no such pronounced effect. In Vertisols, available-P showed significant and positive relationship with saloid P (S-P), occluded P (OCC-P), Ca-P, Org-P and total-P. The Ca-P was found to be positively and significantly correlated with soil pH, available P and negatively correlated with clay. Soil pH bears a significantly negative correlation with S-P, OCC-P, Org-P, total-P and positive correlation with Ca-P. In Aridisols, iron P (Fe-P) showed positive and significantly correlated with organic carbon (OC), clay, available P and negatively with soil pH and Ex-Ca. Multiple regression equations were also worked out for predicting different forms of P in relation to soil properties. About 30% soils of Vertisols are likely to respond to P-fertilizer.