中文摘要：

太湖地区过量施肥现象相当普遍，导致N肥利用率低和N肥损失严重。为此，2004-2006年在中国科学院常熟农业生态实验站进行了连续稻麦轮作试验，研究不同施N量对该地区水稻和小麦产量及N肥利用率的影响，以寻找较为适当的N肥施用量，该施N量即能使作物不减产，又要保持较高的N肥利用率。试验结果表明施N量超过150kg／hm^2后，作物产量增加较少。当施N量从100kg／hm^2增加到350kg／hm^2，连续3年的水稻平均N肥吸收利用率（REN）为46．1％～32．4％，两年小麦试验结果显示小麦的平均REN为36．0％～27．8％。相应的水稻和小麦的农学利用率（AEN）是15．0～5．56kg／kg和17．1～6．91kg／kg。研究还表明太湖地区水稻经济适宜施N量为209kg／hm^2，小麦是219kg／hm^2，在当地作物品种、气候条件和管理方式下，作物产量可分别达到8．2t/hm^2和4．7t／hm^2的高产，水稻的REN、N肥生理利用率（PEN）、AEN、N肥偏生产力（PFPN）可保持为37．6％、29．5kg／kg、11．0kg／kg和44．5kg／kg；小麦则是31．4％、38．4kg／kg、12．0kg／kg和23．7kg／kg。显然，适宜的施N量不仅没使作物减产，而且保证了作物最大的经济效益，并保持了较高的N肥利用率。

英文摘要：

Over nitrogen-fertilization often results in a low nitrogen use efficiency （NUE） and high N loss in Tai lake region. In order to find an optimal N application amount to rice and wheat, field experiments were conducted under different N application amounts from 2004 to 2006. The results showed the crop yield response to added N was very low when N amount exceeded 150 kg/hm^2, and the mean nitrogen uptake efficiency （REN） ranged from 32.41% to 46.11% in three years for rice and from 27. 8% to 36.0% in two years for wheat when N rate was 100 to 350 kg/hm^2, and the corresponding nitrogen agronomy efficiency （AEN） ranged from 5.56 kg/kg to 14.95 kg/kg for rice and from 6.91 kg/kg to 17.1 kg/kg for wheat. The study also indicated that REN, nitrogen physiological efficiency （PEN）, AEN, and partial factor productivity of applied N （PFPN） were 37.6%, 29.5 kg/kg, 11.0 kg/kg and 44.5 kg/kg respectively for rice with N application amount of 209 kg/hm2 and were 31.4%, 38.4 kg/kg, 12.0 kg/kgand 23.7 kg/kg with N application amount of 219 kg/hm2 for wheat respectively. We concluded that the optimal N application amount could not only increase crop yields but also increase the farmer＇s benefits.