Coupling regulation of water and fertilizer in cold farmland of Harbin, Heilongjiang, China, based on resource-benefit-environment synergy

Dry land in Harbin City, Heilongjiang Province, Northeast China Water scarcity, non-point source pollution, and climate change are key challenges to the sustainable use of agricultural water and fertilizers in cold regions. These regions' unique climatic conditions, including freeze-thaw cycles, increase the complexity of managing resources. Current research is insufficient in addressing the feedback mechanisms between crop yield, pollution, and resource use efficiency in response to water cycles during growth and freeze-thaw periods. This study combines field experiments, process simulation, and optimization modeling to develop a sustainable method for regulating water and fertilizers in cold farmland. The results show that optimization increases net economic benefits per cubic meter of water by 18.69 % and reduces pollutant emissions by 20.22 %. Utilizing snowmelt and return water could save 43.8–50 % of irrigation water. Additionally, the impacts of future climate change, including altered crop water demand and precipitation patterns, could lead to a savings in irrigation water. This research provides valuable insights into the physical processes that govern the interactions between water, soil, fertilizers, crop yield, pollution, and resource efficiency, contributing to more effective water and fertilizer management in cold regions. Relationship diagram of agricultural water cycle and pollution migration system. • Quantify relationship between non-point source pollution and soil moisture migration. • Quantify the effect of water cycle in freeze-thaw and growth period on irrigation. • Collaboratively regulate water and fertilizer for eco-env- resource synergy. • Reveal the response of nexus management to climate change. • The use of snowmelt water and return water improves irrigation efficiency.