The Contrasting Ecological Effects of Farmland and Alfalfa Grassland Across Different Planting Scales in the North China Plain

Purpose: Comparing farmland and alfalfa grassland systems under different planting scales in influencing grain yield and environmental security is crucial to achieving sustainable food development. This study aims to evaluate the environmental impacts of farmland and alfalfa grassland systems under different planting scales in the North China Plain. Methods: The environmental impacts, including energy depletion, land utilization, water consumption, global warming, acidification, and eutrophication, were evaluated using robust regression and life cycle assessment (LCA) based on the functional unit of CNY 1000 of grain (crops and alfalfa) production. Robust regression was applied to improve the accuracy of the data, and the LCA method was effectively used to compare the environmental impacts under different planting scales. Results: The comprehensive environmental impact of alfalfa production was 9% lower than that of the crop system in the North China Plain. Compared to large-scale cultivation, smallholder farming resulted in 26%, 34%, and 22% higher environmental impact indicators for alfalfa, maize, and wheat, respectively. Conclusions: The experimental results demonstrate that the robust regression model achieves high prediction accuracy and generalization ability in estimating input–output quantity. The results can provide insights into the optimization of policy initiatives oriented towards the goal of resource-conserving, cost-effective, and environmentally friendly development to facilitate regional planning and sustainable development.