Agricultural non-point source pollution in the Yongding River Basin

• The ESI of agricultural production in the Yongding River Basin is 0.1056.
• Local agriculture is seriously unsustainable.
• Total nitrogen loss is 96 kg hm−2 and total phosphorus loss is 9 kg hm−2.

More and more nitrogen and phosphorus chemical fertilizers are applied in the upstream of the Yongding River Basin. With the aid of convertibility between emergy and value, the calculated ESI (Environmental Sustainability Index) of basin agricultural production is 0.1056, indicating that local agriculture is seriously unsustainable. According to the different combining types of nitrate and ammonium salts with soil particles, soil nitrogen losses under the influence of rainfall-runoff are quantitatively evaluated from the perspective of the nitrogen cycle. By virtue of the content of dissolved and particulate phosphorus in soil, the calculation process for soil phosphorus loss is modeled according to the field runoff volume. The total nitrogen and total phosphorus losses from soil are 96 kg hm−2 and 9 kg hm−2, respectively. The calculation result of nitrogen and phosphorus losses in the basin is certainly reasonable. Finally, the research emphasis of calculation method for reducing basin agricultural non-point source pollution is represented from management level.