中文摘要：

本研究以高丹草（Pacesetter）结合单作春玉米（Zea mays L.）及休闲,探讨华北潮土区夏季多雨时期,牧草、作物及休闲三种土地管理方式土壤剖面0—200 cm NO3--N的分布及运移。研究表明,整个生长季节三种土地管理方式土壤NO3--N逐渐向下层移动,高丹草、玉米地均表现为NO3--N的逐渐耗竭,休闲地则为波浪式上升;种植结束时休闲地在0—200 cm土壤层次硝态氮较种植前增加,高丹草、玉米地则表现为较种植前降低,NO3--N在剖面60—80 cm深度出现积累。与休闲相比,植物对土壤剖面硝态氮的吸收显著减少了硝态氮向深层的淋溶,而休闲却增加了硝态氮向深层淋溶的风险。根长密度及根干重均随剖面深度增加而降低,在0—30 cm土层高丹草明显大于玉米,0—60 cm区域植物根长密度与相应层次土壤NO3--N消减量呈现显著正相关。高丹草对土壤上层氮素的吸收消耗大于玉米,其对截获残留硝态氮,阻止硝态氮大量向下迁移的作用更强,体现出植物吸收的＂安全网＂功能。

英文摘要：

This study was to investigate nitrate distribution and movement in 0200 cm soil layers among three land management systems in summer,such as Sorghum hybrid Sudangrass（Pacesette）,spring maize and fallow in North China Plain.The results showed that soil nitrate in all treatments gradually leached downword during the whole plant growth season,and in the systems of Sorghum hybrid Sudangrass and spring maize it gradually declined,but in summer fallow system it increased with a wave-manner.After harvest,compared with pre-plant,nitrate in 0200 cm soil layers with the treatment of summer fallow enhanced,but of Sorghum hybrid Sudangrass and spring maize it decreased,then accumuled into 60-80 cm soil depth.By contrast with fallow,plant absorption of soil nitrate could significantly reduced the leaching downword,while summer fallow was on the contrary. Root length density and dry weight decreased with the soil depth and the root length density of Sorghum hybrid Sudangrass at soil depth of 030 cm was significant higher than that of maize.There was a significant positive relation between plant root length density and soil nitrate decrease in 060 cm soil layer.Nitrogen absorption in the topsoil of Sorghum hybrid Sudangrass was more than that of maize.This showed that the former had larger capacity to intercept residual nitrate and hold its leaching.It also presented that plant had the function of ＇safety net＇.