中文摘要：

采用外源标记15NO3--N微注射技术的田间微区试验,研究了我国北方灌溉农作体系中,由于氮肥的高量投入导致作物收获后土壤剖面大量残留NO3--N对后作的氮素供应潜力及其去向。结果表明,在本试验水氮管理条件下,菠菜（Spinacia oleraceaL.）对土壤剖面15、457、5 cm位置标记氮的利用率分别为28.2%、22.3%、16.3% 冬小麦（Triticum aestivumL.）小偃54对相应位置标记氮的利用率分别为21.8%、17.4%、11.5%,而京411为21.8%、11.6%、7.4%。菠菜对土壤不同层次残留氮的利用率显著大于小麦,小偃54显著高于京411。菠菜的根长密度低于小麦,土壤剖面多数层次两个小麦品种的根长密度差异不显著,小麦的根长密度与相应土层标记硝态氮的利用率呈显著的正相关关系 根干重在土壤剖面多数层次呈现小偃54〉京411〉菠菜的趋势。生长季结束标记氮发生了向下移动,3个标记处理分别在土壤剖面60—80、60—80、80—100 cm出现积累峰 但菠菜15 cm位置收获后整个剖面的%Ndff值均很低,标记氮在剖面中几乎没有积累峰 不同标记位置的残留氮均发生向上运移,上移距离分别为15、453、5 cm,残留氮标记的层次越深,其在土壤中再分布能力愈弱,残留越集中。

英文摘要：

High input of nitrogen fertilizer caused continuous nitrogen surplus in agro-ecosystem.There were large amount of residual NO-3-N in soil profile after crop harvest in irrigation agricultural system of North China.Nevertheless,the fate and supply potential of the residue NO-3-N for succession crops had been unclear.Field micro-plot experiment and technique of external injection of labeled 15NO-3-N（labeled-N） were used.The results showed that the recovery of labeled NO-3-N in 15 cm,45 cm and 75 cm soil profile by spinach（Spinacia oleracea L.） were 28.2%,22.3% and 16.3% respectively.Those by wheat（Triticum aestivum L.） Xiaoyan 54 in corresponding positions were 21.8%,17.4% and 11.5%,while those by Jing 411 were 21.8%,11.6% and 7.4% respectively,the recovery of labeled NO-3-N in different soil layers by spinach was significantly higher than that by wheat,furthermore,the recovery of labeled NO-3-N by Xiaoyan 54 were significantly higher as compared with Jing 411.The root length density of spinach was lower than that of wheat,and no significant difference of root length density was found in the two wheat varieties in most soil layers.The crop root length density in corresponding soil layers had significant positive correlation with the recovery of labeled nitrate-N;the dry root weight in treatments appeared the tendency with Xiaoyan 545Jing 411spinach in most soil layers.Labeled NO-3-N moved downwards at the end of growing season.The accumulated apices were appeared in soil layer with 6080 cm、60-80 cm、80-100 cm respectively in threelabled experiments.But the%Ndff values of spinach at 15 cm position in the whole profile were all low and the lablednitrogen had scarcely no accumulated apices at the profile.At the same time,the residue nitrogen in different soil layers was all upward migration with 15 cm、45 cm and 35 cm respectively.The deeper of labeled residue nitrogen layer,the weaker of redisbution ability in soil profile and the residue nitrogen was more concentrated.