符合经济生态效益的农田化肥施用量

在洞庭湖区研究了农田化肥的外部成本和经济生态施用量.采用环境影响经济评价方法，估算了化肥的外部成本；运用外部不经济性原理和生产函数模型研究了兼顾农户经济效益、生态效益的农田适宜施肥量.结果表明，2002年洞庭湖区粮食生产中因化肥施用不当而带来的外部成本约为1.35×10⁸元，每千克纯氮的外部成本约为0.3元.在洞庭湖区目前生产条件下，兼顾生产、经济、生态三效益的适宜施肥量是208.26～210.65 kg·hm^-2，相应的粮食产量为5528～5539 kg·hm^-2.2002年洞庭湖区粮食生产实际施肥量已超过农户经济最优施肥量和生态适宜施肥量，建议政府在一些化肥高投入、高污染的地区征收环境污染税.

Optimal chemical fertilizer application rate accorded with local economic and ecological benefits

This paper studied the exterior cost of applying chemical fertilizer on the farmland in Dongting Lake area, one of the main foodstuff production regions in China, aimed to search for an optimal chemical fertilizer application rate accorded with local economic and ecological benefits. The exterior cost was estimated by the method of economic and environmental evaluation, while the optimal application rate was calculated based on Exterior Diseconomy Theory and by using production function model, with both ecological and farmers' economic benefits considered. The results showed that in 2002, the exterior cost of inappropriately applying chemical fertilizer was about 1.35 x 10(8) yuan, equivalent to 0.3 yuan x kg(-1) fertilizer N. Under current situation of test area, the optimal application rate of chemical fertilizer should be 208.26 - 210.65 kg x hm(-2), and the corresponding foodstuff supply would be 5528 - 5539 kg x hm(-2). However, the actual fertilizer application rate in 2002 exceeded the optimal one. A suggestion was made to impose tax for the environmental pollution of over-using chemical fertilizer.