Abstract: [Objective] To assess the physiological response and differential changes of the activities of antioxidant enzymes in feed oat （Avena sativa） to nitrogen fertilizer at the northern foot of Yinshan Mountain, and to determine the optimal nitrogen fertilizer application rate. [Method] Using feed oat species ′Sanxing′ as the material, the nitrogen fertilizer application rates of 0, 150, 200, 250, 300 and 350 kg/hm² were set, and additional 15%, 35%, 30%, and 20% of the nitrogen fertilizer was applied at seedling stage, tillering stage, jointing stage, and booting stage for each nitrogen fertilizer application rate, respectively. The activities of three types of antioxidant enzymes and the level of malondialdehyde （MDA） in feed oat leaves were evaluated at booting stage, heading stage and grain filling stage. [Result] As the increase of nitrogen fertilizer application rates, the activities of superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT） in feed oat leaves at booting stage, heading stage, and grain filling stage increased first and then declined, and the level of MDA reduced progressively. At all of the three observed growth stages, the highest POD activity in feed oat leaves was found at the nitrogen fertilizer application rate of 250 kg/hm². At booting stage and grain filling stage, feed oat leaves had the highest SOD activity at the nitrogen fertilizer application rate of 250 kg/hm². The highest CAT activity was observed at the nitrogen fertilizer application rate of 300 kg/hm² at booting stage and heading stage, and at grain filling stage, that was observed at the nitrogen fertilizer application rate of 250 kg/hm². [Conclusion] At the northern foot of Yinshan Mountain, lower application rate of nitrogen fertilizer enhances the activities of antioxidant enzymes in feed oat, and higher rate exerts the reverse effect. The appropriate nitrogen fertilizer application rate is 250 kg/hm².

Key words: the northern foot of Yinshan Mountain, feed oat, nitrogen fertilizer application rate, antioxidant enzyme