在双季稻区，不同肥力水平稻田的化肥减施潜力还不明晰。本研究针对高中低肥力的双季稻田，通过在养分专家系统（NE）推荐的施氮量基础上设置氮肥增减15%、30%和45%的田间试验，分析了水稻产量及其与氮肥用量的量化关系。结果表明：高中低肥力等级上各处理的早晚稻产量大体呈现出高肥力>中肥力>低肥力的趋势，与低肥力相比，中高肥力的早稻产量提高了2.30%~8.56%，晚稻产量提高了13.56%~17.94%。在NE基础上氮肥减施30%和45%处理下，高中低肥力水平的早稻产量比NE处理降低了8.05%~12.52%，晚稻产量降低了2.03%~6.67%，但低肥力中NE基础上氮肥减施30%的早稻产量则无显著降低。同时，NE基础上氮肥减施15%以及增施15%、30%和45%均不能显著提高高中低肥力水平的早晚稻产量。进一步通过一元二次方程拟合表明，不同肥力等级上早晚稻的产量潜力和对应的氮肥合理用量均呈现出高肥力大于中肥力和低肥力的趋势，养分专家系统可以在实现95%的产量潜力下将氮肥减施12.94%~34.07%，且在维持高产的前提下，高肥力的氮肥减施比例明显低于中肥力和低肥力。因此，在南方双季稻地区，养分专家系统可以在高中低肥力水平实现化肥减施增效，但不同肥力等级氮肥减施比例存在差异。

It is still unclear about the potential of chemical fertilizer reduction among different soil fertility levels in the double-cropping rice area of China. In this study, the field experiments were conducted in the higher, medium and lower soil fertility levels of fields in double-cropping rice area. The treatments were different rates of nitrogen （N） fertilizers, which included the N rate from the Nutrient Expert system （NE） and the N rates increasing or decreasing of 15%, 30% and 45% based on N application rate recommended by NE. Then, the rice yield and its relationship with N rates were analyzed. The results showed that: the yield of early and late rice was followed by higher fertility > medium fertility > lower fertility. Compared with the lower fertility, the yield of early rice in the medium and high fertility levels were increased by 2.30%~8.56%, and they were increased by 13.56%~17.94% in late rice. For the treatment of decreasing 30% and 45% N fertilizer on the basis of NE, the yield of early rice were decreased by 8.05%~12.52% among the higher, medium and lower soil fertility levels than the NE treatment; while their yield of late rice were decreased by 2.03%~6.67%, respectively, excepted for the lower soil fertility. However, compared with the NE treatment, the yield of early and late rice was no significant decrease in the treatments of decreasing N fertilizer by 15% and the increasing of 15%, 30% and 45% N rates on the basis of NE among different soil fertility levels. Furthermore, the yield potential in different soil fertility levels and the corresponding rational amount of N fertilizer were followed that higher fertility was the higher than the medium fertility and lower fertility through the fitting equation. It indicated that the N fertilizer could be reduced by 12.94%~34.07% for 95% yield potential by using the NE model. Meanwhile, the N reduction rate of higher fertility was significantly lower to maintain higher yield than those of the medium and lower fertility levels. Therefore, in the double-cropping rice areas of southern China, the NE model could achieve the reduction of N fertilizer and the improvement of efficiency among higher, medium and lower soil fertility levels. There are differences in the proportion of N fertilizer reduction in different soil fertility levels.