Optimising plastic-film mulching under drip irrigation to boost maize productivity through enhanced water and fertiliser efficiency in sub-humid regions

Global food security is increasingly threatened by the vulnerability of agricultural systems to climate variability, especially in sub-humid regions. Northeast China, a major maize-producing region, experiences low spring temperatures and erratic rainfall, which have prompted the widespread adoption of plastic-film mulching (PFM) combined with drip irrigation. However, systematic evaluations of how different PFM patterns affect crop productivity and resource use efficiency remain limited. This study systematically evaluated three PFM strategies - full ridge-furrow mulching (FM), ridge mulching (RM), and no mulching (NM) - in combination with 240 kg N/ha and a zero-nitrogen control under drip irrigation to determine their effects on maize (Zea mays L.) yield, water use efficiency (WUE), and nitrogen utilisation. Field experiments over two consecutive growing seasons assessed crop growth, dry matter (DM) accumulation, nitrogen dynamics, grain yield, and related efficiency parameters. Both FM and RM significantly enhanced early maize growth. At the seedling stage, FM and RM increased plant height by 43.0% and 40.1%, and leaf area index (LAI) by 141.4% and 120.4% over NM, respectively. During the same stage, DM accumulation increased by 228.9% (FM) and 224.9% (RM). These improvements reflected favourable soil hydrothermal conditions under PFM. Before heading, PFM treatments increased pre-anthesis DM accumulation by up to 19.6%, and at maturity, FM and RM raised DM by 6.1% and 5.1% over NM. PFM significantly improved grain nitrogen accumulation, with FM and RM increasing it by 31.0% and 26.9% over NM, respectively, and nitrogen harvest index (NHI), with FM and RM increasing it by 6.8% and 6.1% over NM, indicating enhanced nutrient translocation to grain. PFM also improved grain yield, with FM and RM increasing it by 15.0% and 13.5%, WUE by 17.2% and 15.7%, and nitrogen partial productivity by 16.8% and 14.1%. No significant differences in yield or WUE were observed between FM and RM. Fertilisation consistently enhanced these benefits without changing the relative efficiency ranking of treatments. Notably, the advantages of mulching diminished after the heading stage as temperature and rainfall increased. PFM (both FM and RM) under drip irrigation improves maize yield, water use, and nitrogen efficiency in sub-humid regions. This integrated practice offers a scalable and sustainable strategy to increase maize productivity and resource efficiency, supporting food security in regions facing similar climatic challenges.