Application of the source-sink landscape method in the evaluation of agricultural non-point source pollution: First estimation of an orchard-dominated area in China

Agricultural non-point source pollution (ANPSP) is a critical cause of global environmental problems. However, the estimation of ANPSP in typical orchard-dominated areas is lacking. In this study, the site conditions and fertilizer application patterns of apple orchard-dominated landscapes in Qixia, north China, were investigated, along with the spatial distribution of land use types, which were obtained through field survey and remote sensing interpretation. Combined with rainfall runoff experiments and an analysis of soil samples and statistical yearbook data, the results revealed that the total N (P) export coefficients of apple orchards, cropland, and builtup land were 68.90 (2.79), 41.58 (1.87), and 4.19 (0.47) kg ha-1 a-1, respectively. Moreover, the areas of extremely low, low, medium, high, and extremely high risks for ANPSP in Qixia were 35,232, 56,514, 62,106, 29,331, and 18 450 ha, respectively, under the current fertilizer application rates of N 545 kg ha-1 a-1 and P2O5 569 kg ha-1 a-1 in apple orchard areas. Two fertilization scenarios were simulated according to local standards; the reduction of the extremely high-risk ANPSP area reached 73.39% in scenario I and 100% in scenario II. In contrast, extremely low-risk areas increased by 14.88% (scenario I) and 218.15% (scenario II). Eventually, a correlation analysis between the source, sink, and current status of ANPSP risks and various environmental factors was conducted. The results showed that ANPSP was significantly positively correlated with the drainage density, water erosion intensity, clay content, and SOC, while it was significantly negatively correlated with the slope, altitude, and the sand content, which indicates the good performance of the source-sink landscape method. Therefore, this method at a source-sink landscape scale may facilitate the evaluation of ANPSP in areas both regionally and worldwide.

Automated summary

This study examined the influence of fertilizer application rates and land use types on agricultural non-point source pollution (ANPSP) risks in apple orchard-dominated landscapes in the Qixia region of northern China. Two fertilization scenarios were simulated to reduce ANPSP risks, resulting in significant reductions in high-risk areas and increases in low-risk areas. Additionally, the results demonstrated the effectiveness of the source-sink landscape method in assessing ANPSP at both regional and global scales.