Abstract: The effect of ureaN application rates on crop yield and nitrate (NO3\|N) leaching were investigated during two winterwheat growing seasons using undisturbed lysimeters in the Taihu Lake Basin of China. The results showed that there was a polynomial rather than a linear relationship between wheat yield and N rates, and the maximum wheat yield was 4.62×103 kg·hm-2 at the N rate of 280 kg·hm-2. However, a significantly positive linear relationship was found between seasonal NO3\|N leaching and N rates, and the seasonal NO3\|N leaching mean values ranged from 4.6 kg·hm-2 NO3-N to 17.1 kg·hm-2 NO3\|N in the five N treatments. It was recommended that the 195 kg·hm-2 N rate was adopted as the optimum ecological application rate of N for wheat in this region, because at that rate, 95% of the maximum yield was ensured while 19.9% of leaching NO3-N reduced compared to that of the maximum yield.

Key words: nitrate leaching, leachate, precipitation, N application rate