| Abstract: The experiment was conducted to probe the regulation of nitrogen application on physiological mechanism and further improve the yield of potato. 'Qingshu No.9' was used as the experimental material to study the effects of nitrogen on the plant height, stem diameter, the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and yield of potato. The results showed that when the amount of nitrogen was 350 kg/hm2, plant height and stem diameter were the highest in the entire growth period of potato. The activity of SOD decreased with the growth period, which reached the highest level on 430 kg/hm2 for nitrogen. When the amount of nitrogen was 350 kg/hm2, the activities of POD and CAT were highest and the average yield per plant was significantly higher than other treatments. Regression analysis indicated that the relations between the yield and the amount of nitrogen application was as follows: y= -0.006 4x2 + 2.641 8x + 115.6 (R2 = 0.887 2**). It was concluded that potato yield (maximum yield was 491.27 g per plant) was highest when the amount of nitrogen application was 206.39 kg/hm2. Therefore, in this experiment, the optimum application amount of nitrogen was 206.39～350.00 kg/hm2 by comprehensive analysis of potato physiological characteristics and yield formation. |