Effect of 32 year long-term integrated nutrient management on soil p fractions and availability of phosphorus under sorghum-wheat cropping sequence in vertisol

Abstract

Study on soil phosphorus (P) fraction is an important aspect in probing the mechanisms of soil P accumulation in farmland and mitigating its losing risk to the environment. We used a sequential extraction method to evaluate the impacts of long-term fertilization and organic manures incorporation on fractions of P of sorghum-wheat sequence in Vertisol. A permanent field experiment was conducted to investigate the effect of 32 year long-term integrated nutrient management treatments (control, Inorganics fertilizers only, Inorganics fertilizers + N substituted FYM, WCS, GM and Farmers practices). The P status of the different soil P-fractions (Saloid-P, Fe-P, Al-P, Red-P, Occl-P and Ca-P) were analyzed from 0-15 cm and 15-30 cm soil depths and their correlation with available-P was studied. It was found that a balanced application of 50% RDF + 50% N-FYM gave highest values of P-fractions followed by 50 % RDF + 50 % N- GM. However, Ca-P content found to be was decreased in treatments integrating organics and inorganics. The sequential order of dominance of different forms of P were Ca-P> Red-P>Al-P>Fe-P>Occl-P>Sal-P. The correlation study reveals that soil available-P is significantly influenced by saloid-P fraction under sorghum-wheat in Vertisol. The current investigation suggests the adoption of integrated nutrient management comprising 50 % RDF + 50 % N-FYM helps to circumvent P-deficiency under sorghum-wheat sequence in Vertisol.