Abstract:The study aims to investigate the effects of different crop straw on key enzymes of nitrogen metabolism of root system and leaves, nitrogen content and soluble protein content in leaves of Jinyousihao during senescence. The results showed that, compared with the control, crop straw significantly increased the root activity, chlorophyll content, nitrate reductase, glutamine synthetase and glutamate synthase activity, while it reduced the glutamate dehydrogenase activity and the content of ammonium nitrogen in leaves (15.6 μg·g^-1). The nitrate content, soluble protein and free amino acid content increased, which effectively maintained a higher level of nitrogen metabolism and delayed the senescence of cucumber. The effect of corn straw returning was the best, for the root activity, nitrate reductase activity and soluble protein content the this treatment were increased by 23.4%, 33.3% and 18.7%, respectively, as compared with the control. Peanut straw showed better effect, with nitrate reductase activity increased by 10.8%. By contrast, rice straw returning showed no significant effect.