Plastic film mulching amplifies yield resilience and stabilizes water use efficiency of winter wheat across wet and dry years on the semi-arid Loess Plateau.

BACKGROUND: Mulching is usually evaluated on multiyear average yield, which hides how its benefit varies with rainfall. A three-year split-plot experiment at Tianshui, Gansu, on the semi-arid Loess Plateau crossed four fertilization levels (no fertilizer, CK; sheep manure, M; mineral, NPK; manure plus NPK, MNPK) with three mulching types (conventional tillage, CT; plastic film with soil cover, FM; film without soil cover, FMS) in three replicates, across two wet years (2022/2023, 2023/2024) and one dry year (2024/2025). RESULTS: Across the 12 combinations, grain yield fell from 6826 kg ha-1 in wet years (n = 72) to 3376 kg ha-1 in the dry year (n = 36), -50.5%. Year type explained 80.3% of yield variance, fertilization 7.2%, and mulching 5.5% (each P < 0.001). Averaged across fertilization levels, the FM and FMS advantage over CT rose from 16.2% and 9.7% in wet years to 38.3% and 37.6% in the dry year, a 2.4- to 3.9-fold amplification; MNPK × CT declined most steeply (-59.1%), a high-fertility trap. Mulching flattened the precipitation-based water use efficiency (WUEp)-precipitation slope from 0.059 (CT) to 0.042 kg ha-1 mm-2 (FMS); year × mulching was significant for WUEp (P = 0.042) but not for yield (P = 0.376). CONCLUSION: Amplification arose from a widened soil-water advantage of mulching over CT (3.7-9.7% in wet years, 11.1-15.8% in the dry year) and a steeper soil-water-yield response under water limitation. MNPK × FM gave the highest three-year mean yield (6656 kg ha-1) at a coefficient of variation of 29.2%, making mulching a precondition for safe fertilizer intensification. © 2026 Society of Chemical Industry.