Long-Term Wheat Residue Management and Supplementary Nutrient Input Effects on Phosphorus Fractions and Adsorption Behavior in a Vertisol

Abstract

The management of crop residues coupled with external nutrient inputs is important for improving and conserving soil fertility and productivity. We assessed the long - term effects of three wheat residue management options (RMO) (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on phosphorus (P) fractions and adsorption behavior of a Vertisol under soybean–wheat system. Wheat residue incorporation and retention improved the labile inorganic P [sodium bicarbonate (NaHCO3 - Pi)] by 3.2 and 5.0 mg kg - 1 and the labile organic P (NaHCO3 - Po) by 2.4 and 4.2 mg kg - 1, respectively, as compared to residue burning. The soils under residue incorporation and retention had 38 and 26% more moderately labile organic P [sodium hydroxide (NaOH - Po)], respectively, than the soil under residue burning. The SNI either as fertilizer or FYM further enhanced NaHCO3 - Pi, NaHCO3 - Po, and NaOH - Po. In contrast, less labile P fractions [hydrochloric acid (HCl) - P and residual - P] remained unaffected by RMO and SNI treatments. Residue retention or incorporation decreased P adsorption over the residue burning for all the three nutrient inputs. The P - adsorption data fitted well to the Langmuir equation (R2 ranged from 0.970 to 0.994). The P - adsorption maximum (b), bonding energy constant (k), differential P - buffering capacity (DPBC), and standard P requirement (SPR) were lower with residue incorporation or surface retention than with residue burning. The SPR followed the order residue burning > incorporation > retention for RMOs and control > fertilizer > FYM for SNI treatments. The NaHCO3 - Pi, NaHCO3 - P0, and NaOH - Po had negative correlation with P - adsorption parameters and showed positive correlation with soybean P uptake. Wheat residue incorporation or retention plus FYM could be an effective strategy for enhancing the P fertility of Vertisols under a soybean–wheat system.