Jun Wang

Intensive agricultural areas across China suffer severe nitrogen surplus, yet its spatiotemporal drivers remain unclear. Using the nutrient balance method, this study quantified cropland nitrogen surplus and its intensity in 47 prefecture-level cities in Beijing, Tianjin, Hebei Province, Shandong Province, and Henan Province from 2010 to 2022. The Geographically and Temporally Weighted Regression (GTWR) model was applied to analyze six driving factors. Nitrogen surplus decreased from 6.71 million t to 4.11 million t, representing a reduction of 38.7%, with a marked decline occurring after 2016. Surplus intensity dropped by 30.7% from 29.13 t/km² to 20.20 t/km², and nitrogen use efficiency rose from 46% to 60%. The GTWR model proved to perform well (R² = 0.749). Both the multiple cropping index and the agricultural industrial structure shifted from positive to negative effects. Specifically, the effect of the multiple cropping index declined from 0.325 to −0.183, showing the largest absolute average annual change. Urbanization rate, agricultural mechanization level, and per capita cropland area exerted negative effects, whereas the agricultural planting structure varied among regions. The multiple cropping index was the most critical factor. Therefore, optimizing cropping systems is an effective pathway to reduce nitrogen surplus. Future research should focus on incorporating climate factors and exploring the interactive effects among driving factors at finer spatial scales (e.g., county level), to achieve more precise nitrogen management.

This research has been performed to optimize the management of cultivated land fragmentation in the Henan Section of the Yellow River Basin, (“the research area”), coordinate the contradiction between increasing food demand and environmental constraints, maintain regional food security, and promote agricultural and rural modernization. The spatial and temporal evolution characteristics have been summarized by calculating the fragmentation index of the cultivated land landscape, and the driving factors explored with geographical detectors. Results show the following: (1) between 2000 and 2023, the landscape fragmentation index of cultivated land in the research region exhibited a pattern of initial decline followed by a subsequent rise. It decreased by 69.33% from 2000 to 2015 and increased by 138.42% from 2015 to 2023. Over the period from 2000 to 2023, the cultivated land landscape fragmentation index in the study area saw an overall reduction of 26.87%. (2) ”The reduction in cultivated land area and the decrease in landscape fragmentation” index accounted for 82.46% in the county unit. (3) The kernel density curve of the cultivated land landscape fragmentation index showed a unimodal distribution, but the shape was flat. The regions with a fragmentation index mainly range from 4 to 6. The regional cultivated land fragmentation distribution was more dispersed. (4) The average altitude, the distance from the Yellow River, the proportion of the construction land area and population density are the main driving factors. The combined impact of the proportion of the construction land area and population density contributes more than 46% to the cultivated land landscape fragmentation index. The interaction among various factors exerts a more pronounced effect than any individual factor alone. The intensity of the main interaction factors reaches above 0.67. The findings of this study can serve as a theoretical foundation for the sustainable utilization and development of cultivated land resources, as well as for ecological protection and construction in the Henan segment of the Yellow River Basin.