Abstract: The difference on the utilization of labeled nitrate-N in different soil layers between two kind of crops, spinach and wheat, as well as two varieties of wheat was studied by means of soil column experiment. The results show that the recovery rate of labeled nitrate-N in spinach, Xiaoyan 54(wheat), Jing 411 (wheat) were 40.7%, 29.9%, 23.4% ; 45.5%, 16.1%, 7.7% and 32.5%, 12.4%, 4.7%, respectively, when nitrate-N was labeled in 10-20, 40-50, 70-80 cm soil layers. Between crops, the recovery of labeled nitrate-N in different soil layers by spinach was significantly higher than that of wheat. And between varieties, Xiaoyan 54 was significantly higher than that of Jing 411. Significant positive correlation was observed between crop root length density in corresponding soil layers and the recovery of labeled nitrate-N. In general, the distribution of nitrate-N in soil profile after harvest in column with spinach was lower than that with wheat, and Xiaoyan 54 was lower than Jing 411. After harvest, the peak of labeled nitrate-N in 10-20 cm layer was moved down to 40-50 cm, while that labeled in 40-50 cm layer did not move downward clearly and that labeled in 70-80 cm layer had the tendency to move upward and accumulated at 60 cm. No significant difference was observed on the moving distance of labeled nitrate-N in different layers between spinach and wheat and between two varieties of wheat.

Key words: Wheat, Spinach, Nitrate-N, 15N, Recovery of labeled nitrate-N, Root system