基于农户个体行为的珠江流域氮、磷营养盐控制政策情景分析

为揭示农户个体行为与流域农业非点源营养盐产生和控制政策之间的逻辑关系,以珠江流域为研究对象,采用系统动力学模型与多主体农户和农村环境管理模型耦合构建流域营养盐污染控制政策的情景分析方法,基于农户在化肥税和农药税组合型政策下的生产行为设计了基准情景、低化肥税情景、中化肥税情景和高化肥税情景4种具有代表性的情景方案,并在各种情景下定量描述流域营养盐对农业政策的响应和评估流域营养盐控制的优选政策方案.结果显示:从农业投入和产出的角度看,2030年低化肥税情景、中化肥税情景和高化肥税情景的化肥施用量相对基准情景分别减少了24.0%、39.8%和50.2%,农药使用量分别减少了27.6%、32.8%和37.4%,农作物产量分别减少了10.0%、16.3%和21.2%,畜禽养殖量分别增加了5.9%、7.5%和14.0%;2030年,基准情景、低化肥税情景、中化肥税情景和高化肥税情景的总氮入河量分别达到94.5、85.1、78.5和75.3万t,总磷入河量分别达到14.0、12.8、12.0和11.6万t;化肥税和农药税的组合型政策能够有效减少营养盐污染量,然而,中化肥税情景和高化肥税情景比低化肥税情景的边际效果小、经济成本高、农作物产出低和畜禽污染高,故低化肥税情景被认为是控制珠江流域营养盐污染的最优方案.

Policies scenario analysis based on the farmers' individual behavior for nitrogen and phosphorous nutrient controlling of Pearl River Basin

To reveal the logical relationship between farmers'' individual behavior and the generation and control policies of agricultural non-point source nutrient in watershed, scenario analysis approaches in watershed nutrient control policies are established based on coupling System Dynamic model with Multi-agent Agricultural household model for Rural Environmental Management model. This research took Pearl River Basin as the research object. This study designs four future scenarios:business-as-usual scenario, low fertilizer fax rate scenario, middle fertilizer fax rate scenario and high fertilizer fax rate scenario, simultaneously with the same pesticide tax rate of 25% for latter three policy scenarios. Under various scenarios, the response of watershed nutrient to agricultural policies is quantitatively described and optimal policy for controlling watershed nutrient is assessed. The results indicate that in low fertilizer fax rate scenario, middle fertilizer fax rate scenario and high fertilizer fax rate scenario for 2030, the quantity of synthetic fertilizer applied will be 24.0%, 39.8% and 50.2% less than that of in business-as-usual scenario, respectively; the quantity of pesticide applied will be 27.6%, 32.8% and 37.4% less than that of in business-as-usual scenario, respectively; crop yield will be 10.0%, 16.3% and 21.2% less than that of in business-as-usual scenario, respectively; the number of livestock will be 5.9%, 7.5% and 14.0% higher than that of in business-as-usual scenario, respectively. In business-as-usual scenario, low fertilizer fax rate scenario, middle fertilizer fax rate scenario and high fertilizer fax rate scenario for 2030, the total nitrogen input to Pearl River Basin will be 9.45×10⁵, 8.51×10⁵, 7.85×10⁵ and 7.53×10⁵ t, respectively; the total phosphorus input to Pearl River Basin will be 1.40×10⁵, 1.28×10⁵, 1.20×10⁵ and 1.16×10⁵ t. The combination of fertilizer tax rate and pesticide tax rate can effectively reduce the discharge of nutrient. Even though middle fertilizer fax rate scenario and high fertilizer fax rate scenario have greater control effects, they have marginal effect, higher economic cost, less crop production and more animal manure pollution compared to low fertilizer fax rate scenario. Therefore, the policy option carried out in low fertilizer fax rate scenario is considered to be optimal for controlling Pearl River''s nutrient pollution.