Spatiotemporal dynamics of soil moisture in edge zones along deep-cut channels of rainfed agricultural plateaus

Edge zones along deep-cut channels in rainfed plateaus are crucial farmlands but suffer persistent soil moisture (SM) reduction that constrain crop productivity. To quantify these dynamics, hourly SM at 10, 40, and 70 cm depths was monitored at three sites (at 3.5, 7, and 11.5 m from the channel edge) during the 2023–2024 apple growing season in the Weibei rainfed Plateau. Results show 8–27 % lower SM in edge zones than inner zones, especially at 40 and 70 cm soil depths, with the strongest impacts during fruit growth stage. Deficits intensified near channel margins due to root uptake by sidewall trees, which consumed 25–43 % of rainfall in growing season. Only heavy rainstorms penetrated deep enough to fully replenish root-zone water, while smaller events provided short-lived relief. The difference in soil water storage (DSWS) between inner and edge zones increased with cumulative reference evapotranspiration and initial DSWS, but declined with greater rainfall depth. In dry years, edge-zone apple trees faced intensified competition from sidewall vegetation, capturing proportionally less rainfall than inner-zone trees. These findings highlight vegetation–rainfall interactions as dominant controls of edge-zone water stress and underscore the need for management strategies that integrate vegetation regulation with rainstorm-mimicking irrigation to sustain orchard productivity in rainfed plateaus.