土壤剖面不同层次标记硝态氮的运移及其后效

 【目的】以北方半干旱湿润区潮土为对象，探讨土壤剖面不同层次硝态氮（NO-3-N）的运移及其后效。【方法】采用外源标记微注射法，设置田间微区试验。【结果】在试验水氮管理条件下，15、45、75 cm 3个标记处理分别向下迁移了65、35、25 cm，但均未移出作物根区（1 m）。播后至冬前3个标记处理100 cm处土壤溶液NO-3-N浓度变动较小，生长后期小麦15、45 cm标记处理出现上升，而菠菜则有所降低，两种作物的75 cm标记处理在整个生长季持续上升，说明作物对75 cm标记硝态氮利用程度较低。夏玉米对前茬标记氮的利用率为2.1%～5.6%，其中以标记45 cm土层处理残效最高；15 cm和45 cm 2个标记深度前茬小麦京411显著高于前茬小麦小偃54。【结论】土壤剖面不同层次累积硝态氮在作物生长季内未发生强烈的淋洗，但表现出上层标记硝态氮移动距离长，下层移动距离短的规律；100 cm处土壤溶液NO-3-N浓度的动态变化可在一定程度上反映作物根区内氮素利用的状况；后茬作物对标记于土壤剖面不同深度的硝态氮的利用是很有限的，与前茬作物吸收、土壤剖面硝态氮的运移及残留密切相关。

Movement and Residual Effect of Labeled Nitrate-N in Different Soil Layers

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.