CAJ | 학술논문

农业经济发展与环境保护是既有矛盾又紧密联系的2个重要问题。为了客观科学地进行农业环境效益和经济效益的评价，该文以位山灌区为例，构建了农业区环境-经济综合效益模型，以农业净收益最大化为目标函数，以环境限制（氮淋失量）为约束，利用 Hydrus-1D 模型模拟计算了不同灌溉和施肥情景下的氮淋失量、根系吸氮量和作物产量，得出作物产量、氮淋失量与灌溉量和施肥量之间的回归方程系数，再利用Matlab优化工具得出不同的氮淋失量控制条件下的灌区优化施肥和灌溉方案。结果表明，农作物净收益随着环境限制条件的放松（即允许氮淋失量的增大）而增加，但增加速度逐渐减缓，表明以牺牲环境达到农业增收的边际效益呈递减趋势。位山灌区在允许氮淋失量为500 kg/hm2（以N计）时的净收益达到最大，相应的灌溉量为240 mm，施肥量为732 kg/hm2（以N计）。如需更严格控制氮淋失量，施肥量将受到限制，可能导致农民净收益减少，政府可通过农业环境补贴的方式进行经济补偿，以鼓励更环保的生产活动。通过科学合理的灌溉量和施肥量指导，可以实现经济效益和环境效益的双赢。研究结果可为灌区农业环境管理和政府环境保护补偿方式的制定提供参考。
농업경제발전여배경보호시기유모순우긴밀련계적2개중요문제。위료객관과학지진행농업배경효익화경제효익적평개，해문이위산관구위례，구건료농업구배경-경제종합효익모형，이농업정수익최대화위목표함수，이배경한제（담림실량）위약속，이용 Hydrus-1D 모형모의계산료불동관개화시비정경하적담림실량、근계흡담량화작물산량，득출작물산량、담림실량여관개량화시비량지간적회귀방정계수，재이용Matlab우화공구득출불동적담림실량공제조건하적관구우화시비화관개방안。결과표명，농작물정수익수착배경한제조건적방송（즉윤허담림실량적증대）이증가，단증가속도축점감완，표명이희생배경체도농업증수적변제효익정체감추세。위산관구재윤허담림실량위500 kg/hm2（이N계）시적정수익체도최대，상응적관개량위240 mm，시비량위732 kg/hm2（이N계）。여수경엄격공제담림실량，시비량장수도한제，가능도치농민정수익감소，정부가통과농업배경보첩적방식진행경제보상，이고려경배보적생산활동。통과과학합리적관개량화시비량지도，가이실현경제효익화배경효익적쌍영。연구결과가위관구농업배경관리화정부배경보호보상방식적제정제공삼고。
Agricultural economy development and environment protection are often contradictory and closely linked in today’s world. For example, fertilizer application in some extent can increase crop production. On the other hand, it also may cause non-point source pollution and aggravate water pollution. In order to evaluate the environmental and economic benefits of agricultural activities objectively and scientifically, an integrated agricultural enviro-economic model was established in this study. The maximum of crop net profit calculated by agricultural input and output is the target function in this model, and the limit condition is the nitrogen loads released to the surface water body and/or groundwater. Thus how to calculate the crop yield and nitrogen leaching is the key issue. The Weishan irrigation district is the fifth irrigation district in China, which is irrigated by the Yellow River. More than 90% of the area is farmland, with rotation of winter wheat and summer maize. As a case study, the Weishan irrigation district was selected for model application because of its homogeneous planting and measurable irrigation. A calibrated and validated Hydrus-1D model was employed to simulate the nitrogen leaching, root uptake of nitrogen and crop yields in several scenarios with different irrigation and fertilization. And then the regression equations were reached between crop yield/nitrogen leaching and the amounts of irrigation and fertilization to get the values of coefficients in the integrated model. Finally, the integrated model was solved by using the optimization toolboxes in Matlab software, and optimal irrigation and fertilization schemes were obtained under different controls of nitrogen leaching. According to the scenario simulations by Hydrus-1D model, nitrogen leaching had a positive correlation with both irrigation and fertilization amounts. Crop yield had a peak value with some optimal irrigation, while no peak value appeared with the change of fertilization for the model’s inner deficiency. Based on the analysis and discussion, the economic benefit would increase as a result of the easing control of pollution (i.e., allowable nitrogen leaching increase), but the growth rate would slow down, that is, the marginal benefit of agricultural development was diminishing at the expense of environment benefit. In the study area, the net income of crops planting was reached the maximum when nitrogen leaching controlled under 500 kg/hm2 with irrigation of 240 mm and fertilization of 732 kg/hm2. If more strict control of nitrogen leaching is expected, fertilization should be decreased, which may reduce the farmer’s income. In this way, government can provide compensation to farmers for encouraging more environment-friendly agricultural production. By using the integrated enviro-economic model, the environmental compensation was about 913.5 Yuan/hm2 if cutting the allowable nitrogen leaching from 500 to 450 kg/hm2. Moreover, scientific guidance of irrigation and fertilization can offer best economic and environmental benefits. For example, if the local actual irrigation of 300 mm and fertilization of 610 kg/hm2 changed with irrigation of 240 mm and fertilization of 458 kg/hm2, the farmer’s income would increase 478 Yuan/hm2, and nitrogen leaching would decrease 123 kg/hm2 at the same time, which may reduce agricultural non-point source pollution remarkably. Although there are some uncertainties in the estimation, this model can be used to provide references for the policy making of agricultural environmental protection and compensation.