Corn residue alters phosphorus sorption and retention dynamics in a leaching-prone soil

Abstract

Agricultural phosphorus (P) runoff contributing to water body enrichment is a major environmental issue, particularly from high-P soils with poor retention. Conservation practices involving crop residues can alter P dynamics. This study quantified the impact of corn stalk residue added on a weight-to-weight basis on P sorption and retention in a leaching-risk soil, examining the influence of pH, ionic strength, and dissolved organic carbon (DOC) on P release. Using batch experiments, we assessed P sorption across varying residue rates (0–20.3 % w/w), P dosages (0–71.8 mg L⁻¹), and P release under different pH (5, 7, 8), ionic strength (0–0.05 M), and DOC concentrations (0–500 mg C L⁻¹). Notably, residue additions above 15.3 % substantially decreased P sorption by 30–50 % and reduced P retention capacity from 90 % to 70 %. Higher P dosages also decreased sorption efficiency (from 56 % to 41 %) and retention (from 91 % to 86 %). Furthermore, P release surged at high pH combined with low ionic strength (0 M), while higher ionic strengths (0.01–0.05 M) buffered this effect. Counterintuitively, despite DOC-derived P inputs, increasing DOC concentrations from 100 to 500 mg C L⁻¹ reduced net dissolved inorganic P from 5.8 % above control to only 0.8 % above control, suggesting rapid P transformation or complexation. These results reveal critical interactions between residue management, DOC dynamics, and soil chemistry, necessitating careful integration of P fertilization strategies with residue practices to mitigate leaching risks while preserving conservation benefits.