基于改进SWAT模型的灌溉—施肥—耕作对乌梁素海流域营养物负荷及作物产量的影响

不合理的灌溉、施肥和耕作是导致乌梁素海流域农业面源污染的主要根源,乌梁素海作为我国北方地区重要的生态安全屏障,多年来面临着湖泊水环境污染、水生态退化等问题,科学开展湖泊水环境综合治理首先要解决流域内农业面源污染问题.研究通过修改土壤水平衡、溶质平衡、地下水平衡和作物生长等模块对SWAT 2012原始版本进行改进,并采用改进的SWAT模型构建了乌梁素海流域分布式水文模型,利用实测径流、硝态氮与总磷排放量、地下水埋深以及作物产量校正和验证模型.基于现状情景,以玉米、葵花和小麦3种主要作物为研究对象,设置了削减灌水量、施肥量及调整耕作方式3种农田管理情景.基于改进SWAT模型不同情景的模拟结果,计算分析各管理情景下的硝态氮与总磷负荷及对各作物产量的影响.结果表明,改进SWAT模型具有良好的模拟效果.不同作物削减5%夏灌水量增产最多达8.41%～10.32%,削减10%秋浇水量均明显减少硝态氮和总磷负荷.不同作物营养物负荷均随着氮磷施肥削减比例的增大呈现逐渐降低的趋势,但下降曲线逐渐趋于平缓;各作物产量随氮磷施肥削减比例的增加呈先增加后减少的趋势,其中玉米、小麦氮磷施肥削减比例达20%时产量开...

Effects of irrigation-fertilization-tillage on nutrient loading and crop yield in Ulansuhai watershed based on improved SWAT model

Irrational irrigation, fertilization and farming are the main causes of agricultural non-point source pollution in Ulansuhai watershed. As an important ecological security barrier in northern China, Lake Ulansuhai has been facing problems, such as lake water environment pollution and water ecological degradation. To achieve the integrated management of lake water environment, agricultural non-point source pollution in the watershed must be controlled. The study improved the original version of SWAT 2012 by modifying the modules of soil water balance, solute balance, groundwater balance, and plant growth. A distributed hydrological model of Ulansuhai watershed was constructed with the improved SWAT model, which was calibrated and validated with measured runoff, nitrate nitrogen (NN), total phosphorus (TP) emissions, groundwater depth and crop yield. Three scenarios including reduced amount of irrigation, fertilization, and adjusted farming mode based on the current situation were applied on three main crops (corn, sunflower and wheat). NN and TP loadings and their effects on the crop yields under different management scenarios were simulated using the improved SWAT model. The results showed that the improved SWAT model has a good simulation fitting. For different crops, reducing the irrigation amount by 5% in summer can increase production by up to 8.41%-10.32%, and reducing 10% irrigation in autumn will significantly reduce the NN and TP loadings. The nutrient load of different crops showed a decreasing trend with an increasing reduction ratio of nitrogen and phosphorus fertilization (NPF), but the declining rate gradually became smaller. The yields of different crops increased first and then decreased with the ratio of NPF increase. When the ratio of NPF reduction reached 20%, the yield of corn and wheat began to decline, and when it reached 25% the yield of sunflower began to decline. The nutrient loads and wheat yield of different crops gradually decreased with an increase of the mixing depth and efficiency of the tillage mode, while the yield of corn and sunflower gradually increased with the tillage parameters. If combining cutting 5% of summer irrigation, reducing 20% NPF amount, and the template plowing combination, corn yield could increase by 36.5%. If cutting 10% of autumn watering, reducing 25% NPF, the template plowing combination, sunflower nitrate nitrogen load could reduce by 42.1%. If cutting 5% of summer irrigation, 20% reduction NPF, and no-tillage combination, wheat yield could increase by 29.1%. However, cutting 5% of autumn watering, 20% reduction NPF and conventional spring ploughing combination, NN loading of wheat farming could reduce by up to 27.2%, and TP loading could reduce by up to 18.5%. This research can provide a scientific basis for the implementation of agricultural management measures to reduce non-point source pollution, increase crop yields in Ulansuhai watershed and reduce the nutrients loads in Lake Ulansuhai.