Abstract: Abstract: This study set up field micro-plot experiments by technique of external injection of labeled 15NO-3-N to investigate the movement and aftereffect of labeled nitrate-N in different soil layers. The results showed that，under the condition of experimental water and nitrogen management, in the crop growth season no NO-3-N intensively poured, labeled NO-3-N in soil depth of 15cm, 45cm and 75cm moved downwards 65cm, 45cm and 25cm respectively, which no moved outside crop root zone (1m). These presented the regulation of labeled NO-3-N in upper soil layer moving in longer distance and those in subsoil in shorter distance. Labeled NO-3-N dynamic regulation in soil solution 100 cm depth frankly reflected N utilization status. From after-sowing to before-winter, labeled NO-3-N concentration in those three treatments changed less. But at the growth-evening stage, for wheat it increased in soil depth of 15 cm and 45 cm and for two crops it increased in 75 cm layer until harvest, which showed that N utilization in 75 cm soil layer were lower. In summer maize growth season, labeled-N utilization ratio was from 2.1% to 5.6%. The remnant efficiency in different labeled-N treatments collectively represented higher in soil depth of 45 cm and lower in 15 cm and 75 cm. And in summer maize planted behind Jin411 it was significantly higher than those planted behind Xiaoyan54 in soil depth of 15 cm and 45 cm, the value in the former was higher than those in the latter in soil depth of 75 cm, but no significant.

Key words: 15N, Wheat, Spinach, Maize, Utilization ratio of nitrate-N