Peanut‐Based Rotations Improved Soil Aggregate Stability, Nitrogen Pools and Soil Quality in Huang‐Huai‐Hai Plain

Legume symbiotic nitrogen fixation can substantially modify soil nitrogen composition; however, its influence on soil aggregation and nitrogen dynamics under legume‐based rotations remains insufficiently understood. Therefore, this study evaluates the effects of peanut‐based rotations on soil quality by examining changes in soil aggregation and nitrogen pools. A six‐year field experiment was conducted in the Huang‐Huai‐Hai Plain of China, using the conventional winter wheat–summer maize (WM) rotation as control. Four peanut‐based rotations were tested: winter fallow–spring peanut (CP), winter wheat–summer peanut (WP), wheat–maize followed by fallow–spring peanut (WMP) and continuous wheat–maize followed by wheat–peanut (WMWP). Soil samples from 0–20 cm (topsoil) and 20–40 cm (subsoil) were analysed for aggregate distribution and stability, aggregate‐associated nitrogen, soil nitrogen fractions and soil quality index (SQI). The results showed that large macroaggregates ( A LM ) dominated soil structure across depths (47.77%–63.18%) and accounted for most aggregate‐associated nitrogen (48.11%–61.26%). The WP rotation significantly increased A LM proportion and aggregate stability, as shown by higher mean weight diameter (+5.75%–14.60%) and geometric mean diameter (+5.03%–10.12%). WP and WMWP modes increased topsoil acid‐hydrolysable nitrogen, whereas CP and WMP reduced most organic nitrogen fractions. Compared with CP and WM, WP, WMP and WMWP significantly increased NO 3 − –N concentration by 48.41%–90.75% in the topsoil and by 74.24%–136.41% in the subsoil, and increased dissolved nitrogen fractions by 36.19%–179.95% and 25.61%–113.26%, respectively. Consequently, SQI improved markedly, with CP, WP and WMWP increasing topsoil SQI by 24.56%–57.70% and subsoil SQI by 59.06%–74.27%, whereas WMP enhanced subsoil SQI by 54.27%. Partial least squares path modelling revealed that aggregate structure is a key regulator of nitrogen dynamics, particularly for active and organic fractions and highlighted enhanced crop diversity and aggregate stability as the main drivers of SQI improvement. Overall, these results demonstrate that peanut‐based rotations, particularly WP and WMWP, improve soil quality by strengthening aggregate stability and promoting nitrogen retention. Legume‐based diversification provides an effective pathway to sustainable intensification in intensive agroecosystems.