ABSTRACT

In Tai Lake region, rice yield and its benefit responded to nitrogen rate in a convex parabolic curve based on results simulated by ORYZA v3 model, yet the nitrogen loss and its environmental damage responded in a concave parabolic curve. Assuming the partial income equal to the partial loss, optimal nitrogen rate trade-offed the rice productivity and environmental damage (ONR_EB) were determined under different rice and nitrogen price regimes. ONR_EB varied within the ranges of 215.4–294.1 kg N ha⁻¹ and 238.1–313.8 kg N ha⁻¹ in alternate wetting and drying (AWD) and flooded (FI) paddies. With rice price as 0.385–0.400 US$ kg_Y⁻¹ and price of nitrogen pollution as 0.308 US$ kg_N ⁻¹, ONR_EB was estimated as 289–291 and 310–312 kg N ha⁻¹ in AWD and FI paddies. When nitrogen price increased to 2.462 or 3.077 US$ kg_N⁻¹, ONR_EB will reduce to 247–252 or 236–242 kg N ha⁻¹ in AWD paddies and 269–273 or 259–264 kg N ha⁻¹ in FI paddies. Pricing nitrogen at a relatively high level (by incorporating cost for its environmental damage) or guiding farmers to increase their expected income will be an efficient tool for local government to reduce the nitrogen inputs in rice production.

摘要

根据ORYZA v3模型模拟结果，太湖地区水稻产量及其效益对施氮量呈凸抛物线响应，而氮素损失及其环境损害呈凹抛物线响应。假设部分收入等于部分损失，最佳施氮量权衡水稻生产力和环境损害 (ONR _EB ) 是在不同的水稻和氮价格制度下确定的。在干湿交替 (AWD) 和淹水 (FI) 稻田中，ONR _{EB在 215.4–294.1 kg N ha} ^-1和 238.1–313.8 kg N ha ^-1范围内变化。大米价格为 0.385–0.400 美元 kg _Y ⁻¹和氮污染价格为 0.308 美元 kg _N ^-1，ONR _EB在 AWD 和 FI 稻田中估计为 289-291 和 310-312 kg N ha ^{-1 。}当氮价格上涨至 2.462 或 3.077 美元 kg _N ^-1时，ONR _EB将在 AWD 稻田中减少至 247-252 或 236-242 kg N ha ^-1 ，在 FI 中减少至 269-273 或 259-264 kg N ha ^-1稻田。将氮定价在相对较高的水平（通过纳入其对环境的破坏成本）或引导农民增加预期收入将是地方政府减少水稻生产氮素投入的有效工具。