To comprehensively evaluate the reduction potential of diffuse nitrogen pollution under the field-ditch-pond system optimization, a watershed hydrological model was used to simulate the multi-scenario optimization of field ponding water level, ditch, and pond in a typical paddy field watershed. Results showed that different optimizations had different interception effects on diffuse nitrogen pollution, and that interception effects were different over distinct hydrological years. Under the optimization of field ponding water level, the total nitrogen loss from paddy fields after optimizing the drainage water level was reduced by 7.9% to 93.9% compared to conventional water level management, with the nitrogen interception effect being better in dry years than in wet years. Under ditch optimization, the reduction rate of nitrogen loss in the watershed increased from 0.8% to 26.7% after increasing the grass planting density of ditches, with the nitrogen interception effect being better in wet years than in dry years. Under pond optimization, the reduction rate of nitrogen loss in the watershed increased from 10.5% to 18.1% after increasing the catchment area of the pond, with the nitrogen interception effect being better in dry years than in wet years. Under the multi-optimization of the field-ditch-pond system, the interception effect of field ponding water level optimization on watershed nitrogen loss was better than that of pond optimization and ditch optimization. In summary, the multi-optimization of the field-ditch-pond system can effectively control the diffuse nitrogen pollution in paddy field watersheds and could promote the sustainable development of rice production.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |