Integrating green manure and organic amendments enhances nutrient–yield coupling and system resilience in dryland wheat

Context Dryland wheat systems on the Loess Plateau of China are increasingly constrained by erratic rainfall and ongoing soil degradation. The traditional summer fallow, intended for water storage, fails to restore soil fertility or sustain productivity. Under intensifying climate variability, improved management strategies are urgently needed. Objective This study tested whether integrating legume green manure with organic amendments (straw, manure, or both) could transform the summer fallow from a passive water-storage phase into an active biological stage, thereby enhancing yield stability, soil fertility, and system resilience. Methods A seven-year split-plot field experiment (2016–2023) was established in a rainfed winter wheat system on the Loess Plateau, China. The main plot compared two summer fallow systems: conventional fallow (G₀) and legume green manure incorporation (G). Subplots included five fertilization regimes: mineral fertilizer alone, mineral fertilizer combined with manure (M), straw (S), or their combination (MS). Results Replacing summer fallow with green manure initially reduced yield by 8–14 % but produced a 14.4 % advantage during the 2023 drought after a 3–5-year transition. The green manure system (G) enhanced crop nitrogen and phosphorus uptake primarily via soil nutrient pool expansion, whereas nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) showed strong interannual variability rather than consistent increases across years. Among treatments, the G-M achieved the highest yield, whereas G-MS most effectively enhanced soil nutrient stocks (0–60 cm) and maintained comparable nutrient uptake to G-M. Path analysis indicated that 61 % of the total yield effect occurred indirectly through nutrient-pool expansion and enhanced nutrient uptake. Conclusions Replacing summer fallow with green manure shifted system management from water conservation to soil fertility renewal. The G-M pathway supports short-term productivity through fast nutrient turnover, whereas G-MS builds long-term resilience by expanding soil nutrient capital and sustaining nutrient cycling. Significance Integrating green manure with organic amendments offers a flexible and scalable approach to strengthen soil function, enhance nutrient–yield coupling, and build climate resilience in dryland wheat systems.