Phosphorus Forms under Crop Residue Retention and Phosphorus Fertilization in Maize-Wheat Rotation

A field experiment was initiated in 2013 with maize-wheat cropping system to study the effect of crop residue (CR) and phosphorus (P) management on different P fractions in soil. Residue retention treatments, viz., no-CR, 25% CR, 50% CR, and 75% CR in main plots and P fertilizer rates, i.e., no-P, 50% recommended dose of P (RDP), 100% RDP, 150% RDP, and 50% RDP + P solubilizing bacteria (PSB) and arbuscular mycorrhiza (AM) in sub-plots were laid out in split-plot design with three replications. The results of this study reveal that the surface retention of CR along with P fertilization has the potential to improve soil P fertility by increasing Olsen-P and organic P fraction. As compared to control, the aluminum bound P, iron bound P, calcium bound P, and reductant soluble P fractions in surface soil decreased from 30.3 to 27.3 mg kg(-1), 44.7 to 31.3 mg kg(-1), 265 to 227 mg kg(-1), and 121 to 110 mg kg(-1), respectively, with CR retention, while soluble and loosely bound P was increased from 6.11 to 7.64 mg kg(-1) with CR retention. The beneficial effect of P fertilizer application on soil P fertility was further enhanced with the supplementation with PSB and AM.