Changes in P fractions and sorption in an Alfisol following crop residues application

• Published in: Journal of plant nutrition and soil science 2005-04, Vol.168 (2), p.241-247
• Main Authors: Reddy, D.D, Rao, S.A, Singh, M
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alfisol; Alfisols; application rate; Biological and medical sciences; crop residue; crop residues; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Glycine max; P sorption; phosphorus; phosphorus fertilizers; sequential P fractionation; soil amendments; soil chemistry; soil fertility; soil labile P; Soil science; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; sorption; topsoil; Triticum aestivum
• ISSN: 1436-8730; 1522-2624
• DOI: 10.1002/jpln.200421444

With the emphasis on sustainable agriculture, attention has been increasingly turning to recycling of crop residues as a component of fertility management strategies for tropical soils. We assessed the effects of soybean residue (SR) and wheat residue (WR) applied either alone or in combination with fertilizer P (FP) on dynamics of labile P, distribution of P fractions, and P sorption in a semiarid tropical Alfisol by conducting a 16 w long incubation experiment. The amount of P added through crop residues, FP or their combinations was kept constant at 10 mg P (kg soil)–1. Addition of SR or WR resulted in net increase of labile inorganic (Pi) and organic P (Po) and microbial P throughout the incubation period, except that the WR decreased labile Pi during first 2 w due to Pi immobilization. The P immobilization associated with WR addition was, however, offset when fertilizer P was combined with WR. Generally, the increases in labile‐P fractions were larger with the SR and SR+FP than with the WR and WR+FP. The sequential fractionation of soil P at the end of 16 w indicated that a major part of added fertilizer P transformed into moderately labile and stable P fractions as evident from the increased NaOH‐Pi and HCl‐P in the FP treatment. In contrast, the addition of SR and WR alone or in combination with FP favored a build‐up in NaHCO3‐Pi and ‐Po and NaOH‐Po fractions while causing a decrease in NaOH‐Pi and HCl‐P fractions. The addition of these crop residues also effectively decreased the P‐sorption capacity and hence reduced the standard P requirement of the soil (i.e., the amount of P required to maintain optimum solution P concentration of 0.2 mg P l–1) by 24%–43%. Results of the study, thus, imply that soybean and wheat crop residues have the potential to improve P fertility of Alfisols by decreasing P‐sorption capacity and by redistributing soil P in favor of labile‐P fractions and promoting accretion of organic P.