农田水利改革、增产激励与面源污染风险——基于云南陆良县改革试点的实证研究

Irrigation reform,yield stimulation,and risk of non-point source pollution:evidence from a pilot region in Luliang County,Yunnan

过度施肥导致的农业面源污染问题制约着我国农业发展,而完善农田水利设施、加强农业用水管理是促进农业可持续发展的重要举措。国家正在推进的农田水利改革能否在促进农业用水方式改变的同时减少农业面源污染,是值得关注的问题,但目前学界较少从农田水利改革视角为农业面源污染的防治提供新的理论与实践依据。本研究利用云南省陆良县的农户调查数据,通过多元回归模型探索农田水利改革对当地农田氮、磷面源污染排放量的影响,并采用中介效应模型进一步分析其作用机制。结果表明,就灌溉区位条件较差的研究区域而言,在农业活动外部性约束机制尚未建立的背景下,农田水利设施的完善会导致农田氮、磷面源污染排放量增加,这与农户的增产激励行为紧密相关。具体来看,农田水利改革改变了试点村农户的轮作方式、种子用量及灌溉用水量,即由改革前早春农田撂荒或马铃薯少量种植向复耕或扩大马铃薯种植规模转变,农田种子用量及灌溉用水量增加,使得当地农田面源污染风险增大。此外,非农就业比例在农户增产激励行为与农田水利改革之间发挥了一定的调节效应。在灌溉基础相对薄弱的地区进行农田水利改革时,应同步推进农田节水灌溉以及化肥减施、适施等行动,提高农户节水节肥意识,适时开展农业绿色生产技术推广,积极发展农业社会化服务。

Agricultural non-point source pollution caused by excessive fertilization is hindering China′s agricultural development.Improving farmland irrigation facilities and strengthening agricultural water management are important measures to promote the sustainable development of agriculture.Thus,exploring whether the ongoing reform can simultaneously improve agricultural water management and control non-point source pollution is of great significance.However,few studies have provided a theoretical and practical basis for non point source pollution control,especially from the perspective of agricultural irrigation and water conservancy reform.Based on the survey data collected in Luliang,Yunnan,we investigated the impact of the agricultural irrigation and water conservancy reform on local non-point source pollution emissions using the multiple regression model.Furthermore,we analyzed the mechanism driving the impact using the intermediary effect model.Our findings suggest that,in the villages with relatively poor irrigation systems,the reform increased the emissions of N and P non-point source pollution in the case of the absence of intervention for the externalities in agricultural activity.The increasing emissions were found to be closely related to farmers′short-term motivation to increase the volume of agricultural production.Specifically,the reform has changed the pilot villages′crop rotation,which is captured by the re-cultivation or expansion of abandoned lands for planting spring potato,and also increases the irrigation water use and seed consumption.These changes in agricultural production arising from the reform eventually aggravate local non-point source pollution.Moreover,the yield stimulation is moderated by non agricultural employment.Our findings provide some policy implications for areas with poor irrigation systems,the irrigation and water conservancy reform should keep pace with guiding farmers′proper application of chemical fertilizers,increasing their environmental awareness,promoting green technologies in agricultural production,and supporting agricultural socialized services.