White film cover improves water productivity and reduces carbon emissions of spring wheat farmland in the arid region of Northwest China

Crop water consumption and carbon emission (CE) vary under different mulching conditions, but limited research has been done on how black film (BM) and white film (WM) mulching affect the CO2 budget in wheat fields. To investigate the impact of different mulching practices on farmland CE and develop effective agricultural mulching strategies for emission reduction, water conservation and high efficiency, the study was carried out on spring wheat in the arid region of Northwest China. BM and WM mulching treatments were applied, with bare-ground no mulch cultivation (NM) as the control. Net ecosystem carbon exchange (NEE) was continuously measured using automated open canopy-chamber systems. Mulching significantly improved soil water storage and promoted wheat growth. During the jointing stage, BM enhanced vegetative growth and increased soil water consumption. After the jointing stage, WM increased the number of effective tillers and promoted physiological growth, along with increased soil water consumption. CO2 absorption followed a general pattern of WM > NM > BM from the jointing to the heading stage. At midday, BM experienced reduced CO2 absorption ("avoidance" phenomenon), while WM maintained high CO2 absorption, resulting in stronger NEE compared to BM (increased by 17.43 % in 2023 and 14.48 % in 2024). Concomitantly, increased stomatal conductance contributed to higher CO2 absorption. WM also promoted photosynthesis through higher relative leaf chlorophyll content, which in turn improved tiller differentiation, dry matter accumulation, and water productivity (WP). In conclusion, the use of WM in spring wheat in the arid region of Northwest China proved to be an effective method for reducing CE and increasing WP.