Maize‐Green Manure Intercropping Enhances Soil Health and Water Storage on Newly‐Built Terraces of the Loess Plateau

ABSTRACT Newly‐built terraces on the Chinese Loess Plateau have low soil organic carbon (SOC), weak structure, and chronic water limitation. This study hypothesized that during the maize‐green manure co‐growth stage, when maize is at the seedling stage with relatively low water demand, intercropped green manure can utilize soil moisture and convert it into biomass with limited additional water stress on maize. Green manure root growth and returned aboveground biomass increase SOC input, promote soil aggregates formation and stability, thereby enhancing soil structure, porosity and soil water‐holding capacity. Consequently, during the maize‐independent growth stage, soil can store more water, providing a more stable water supply for the later growth stages of maize. A two‐year (2023–2024) field experiment was implemented in Yan'an City, Shaanxi Province, and five treatments were set up: maize monocropping (M), maize‐hairy vetch intercropping (M‐H), maize‐rape intercropping (M‐O), maize‐ryegrass intercropping (M‐R), and maize‐soybean intercropping (M‐S). This experiment measured soil aggregates size distribution and stability, SOC within aggregates, SOC, soil water storage (SWS), biomass, and yield. Intercropping increased SOC relative to monocropping (2.34%–6.19%) and shifted SOC from silt‐clay to macroaggregates pools; M‐R treatment consistently produced the highest macroaggregates proportion and stability indices. Maize yields under M‐H, M‐R, and M‐S treatments improved by 17.78%, 18.43%, and 9.06%, respectively, compared to the M treatment over the two‐year average. However, yields under the M‐O treatment decreased relative to the M treatment, reflecting more intense competition for water in the early growth stages. SWS decreased during the maize‐green manure co‐growth stage (“water‐for‐carbon” trade‐off) but increased during the maize‐independent growth stage, especially under M‐R treatment, indicating a “structure‐for‐water” benefit. Overall, M‐R is a practical option to enhance SOC, improve soil structure, increase late‐season SWS, and raise maize yield on water‐limited newly‐built terraces.