Three-year field experiments were conducted to investigate the effects of ridge film mulching plus furrow planting (RFMF) and traditional flat planting (FP) on the seed quality, oil yield and nitrogen-use efficiency of winter oilseed rape (Brassica napus) and to determine the optimal rate of nitrogen (N) application under the two planting patterns. Six N rates, 0, 60, 120, 180, 240 and 300 kg N ha⁻¹, were applied under both patterns. RFMF significantly increased seed yield, oil yield, N agronomic efficiency (NAE) and N partial factor productivity (NPFP) by 15.5–43.5%, 18.0–48.3%, 2.1–70.6% and 17.9–48.2% respectively, compared with FP. The optimal N application rates were 235 and 218 kg N ha⁻¹ under RFMF and FP, respectively. In conclusion, RFMF could be adopted with N rate of 235 kg N ha⁻¹ for the cultivation of winter oilseed rape in northwest China to improve shoot nutrient uptake, oil yield and N use efficiencies.

Warming is making drought and heat co-occur more often, intensifying compound stress on cropland in northern China’s drylands, where water scarcity makes further irrigation expansion untenable. On the Guanzhong Plain, a major grain-producing region, it remains unclear which irrigation conditions buffer cropland carbon–water productivity—the carbon assimilated per unit of water consumed—against such events. Using growing-season (March–October) remote sensing for 2016–2024, we identified the 2022 compound drought–heat event pixel by pixel and classified cropland as stable rainfed, transitional/mixed, or stable high-coverage irrigation from the pre-event (2016–2020) irrigated-area fraction and its persistence. In 2022, 88.9% of cropland experienced at least one compound dry–hot day, with dry–hot overlap 2.4 times the independence expectation. After balancing climate, terrain, soil, spatial position, and subpixel cropland fraction, stable high-coverage irrigation held no advantage in event-year resistance, post-event recovery, or overall resilience. Carbon assimilation remained above its pre-event level while carbon–water productivity fell, so the event cost water-use efficiency rather than carbon. Event-period root-zone soil-moisture change ranked first, and irrigated-area fraction last, among twelve random-forest predictors of resistance. We flagged 6722.3 km² of cropland for water-use audits and 2418.1 km² for supplemental irrigation; limited water should be allocated by realized moisture status, exposure, and resilience, not by irrigability.