Three‐Year Assessment of Nitrogen Losses, Greenhouse Gas Emissions and Carbon Footprints in Film Mulching Maize Fields: Impacts of Fertiliser Management

ABSTRACT Plastic film mulching (FM) is widely used to increase crop yields and nitrogen (N) use efficiency. Slow‐release fertilisers (SRF) and nitrification inhibitors (e.g., dicyandiamide [DCD]) are promising for reducing soil N losses, but their combined effects on N balance and carbon footprints (CF) in dryland spring maize systems remain unclear. A 3‐year field experiment on China's Loess Plateau evaluated two cropping patterns: non‐mulching (NM) and FM, combined with three fertilisers: conventional urea (CU), SRF and urea with DCD (UD). The study assessed N loss pathways (N 2 O, NH 3 , NO 3 − leaching), N mineralisation, maize yield and CF. Both FM and SRF/UD reduced NO 3 − leaching, with FM‐SRF being most effective while achieving the highest yield (13,981 kg ha −1 ). FM and SRF/UD had contrasting effects on N 2 O and NH 3 , with FM exerting a greater influence. FM increased N 2 O but decreased NH 3 , with the smallest N 2 O rise in FM‐UD and the largest NH 3 reduction in FM‐SRF. Primary N loss pathways were NO 3 − leaching (16%–52%) and NH 3 volatilisation (53%–83%). FM's impact on CO 2 emissions was smaller than fertilisation effects; FM‐SRF minimised N mineralisation, enhancing soil organic carbon (SOC) storage and reducing CO 2 emissions. FM‐SRF achieved the lowest greenhouse gas intensity (GHGI: 0.017 kg CO 2 ‐eq k g −1 ). ΔSOC dominated total CF (26%–62%), while N loss contributions were minor (3.4%–8.8%). FM‐SRF achieved the lowest total CF (4680 kg CO 2 ‐eq ha −1 ) and lowest CF per unit yield. Thus, SRF is optimal for film mulching spring maize systems, ensuring low CF and N losses in Loess Plateau drylands.