Regulation of Potassium Distribution Within Soil Aggregates by Combined Straw and Milk Vetch Incorporation in Double‐Season Rice Fields

ABSTRACT Double‐season rice fields typically exhibit low soil potassium (K) availability despite abundant straw resources. Whether integrating milk vetch could enhance K retention from straw and improve its uptake by subsequent rice remains unclear. Therefore, we examined how the combined incorporation of straw and milk vetch affects soil K distribution and bioavailability. A field experiment conducted in Jiangxi Province, China, which treatments included single straw incorporation (S) and combined straw plus milk vetch incorporation (S + G). The exchangeable and non‐exchangeable K of bulk soil in S + G were higher by 79.33% and 22.26% than the S treatment. Compared with the S treatment, the S + G also improved the exchangeable and non‐exchangeable K in > 2 mm, 0.25–2 mm, and 0.053–0.25 mm aggregates. Notably, milk vetch strengthened the linkage between exchangeable K and non‐exchangeable K within microaggregates (0.053–0.25 mm). These results demonstrate that integrating straw with milk vetch effectively enhances soil K availability for double‐season rice systems.