The Difference in the Effects of Black and Transparent Mulching Films in Dryland Maize Production: From the Perspective of Soil Nitrogen Cycling to Plant Root-Shoot Physiology

In the context of global warming, dryland agricultural production faces dual stresses of high temperature and drought. While transparent plastic film mulch has effects of warming soil and conserving moisture, its excessive warming tendency can exacerbate thermal stress in the root zone of rainfed maize, leading to root senescence, inhibition of photosynthesis, and yield fluctuations, especially in warm-dry ecological regions where maize yield reductions of 5%-10% may occur. Due to its unique optical properties, black plastic film can maintain soil moisture while moderately regulating root-zone temperature, making it a key technical pathway for replacing transparent film. This paper systematically elaborates on the differences in the effects of black and transparent plastic film on dryland maize production from the perspective of soil nitrogen cycling to plant root-shoot physiology. From a soil-process perspective, transparent film significantly increases soil temperature, accelerating nitrogen mineralization and nitrification. Although this enhances the supply of available nitrogen in the short term, it worsens organic nitrogen pool depletion in the long run and raises the risks of nitrogen leaching and gaseous nitrogen loss. In contrast, black film moderates soil temperature, maintains relatively stable microbial activity and nitrogen transformation processes, coordinates the “supply-demand-loss” relationship of nitrogen, and promotes efficient nitrogen-fertilizer use. From a plant-response perspective, the high-temperature stress induced by transparent film inhibits root activity and nitrogen uptake, resulting in premature leaf senescence and disrupted allocation of photosynthetic carbon. Black film alleviates heat stress on the root zone, extends leaf greenness duration and grain-filling period, and optimizes source-sink relationships. Based on the above mechanisms, black film has a significant advantage in increasing and stabilizing yield in areas with an annual average temperature above 9 ℃ and a precipitation of 400 mm during the growing season. On average, it can increase maize yield by 7% to 17%. Future rainfed maize production should rely on accumulated-temperature-precipitation coupling models to define ecological application thresholds for the two film types, focus on rhizosphere microbial-ecological responses to warming, integrate drip irrigation under mulch with controlled-release fertilizer technology, and establish a climate-smart mulching model that coordinates water and fertilizer management. Through the integration of multiple technologies and mechanistic innovation, black film mulching technology is expected to provide a systematic solution for the sustainable development of dryland agriculture under global warming.