【作者】 王珏；

【导师】 张丽娟； 李慧卓； 巨晓棠；

【作者基本信息】 河北农业大学 ， 土壤学， 2009， 硕士

【摘要】 氮素是人类提高粮食产量的巨大动力,然而经过长期不合理的氮肥投入,中国农田土壤已累积了大量的硝态氮,对地下水构成了严重威胁。如何解决土壤深层硝态氮高累积的问题备受人们专注。本研究分别采用外源15NO3--N注射法和硝态氮高累积剖面田间原位试验方法,通过不同根系植物和种植方式,设置田间微区试验和田间小区试验,对不同根系作物及种植方式对土壤中累积硝态氮的利用及残留运移趋势进行探讨,从而筛选出适宜的植物种类及种植方式,并且得出了以下结论:1在常规田间管理条件下,15N微注射微区中,当季苜蓿-无芒雀麦、苜蓿、春玉米、鸭茅及黑杨对深层标记15N利用率分别为18.4%,14.5%,11.0%,9.5%和7.0%;苜蓿-无芒雀麦显著高于玉米、鸭茅和黑杨;玉米显著高于鸭茅和黑杨。第二年对应为11.8%,8.9%,14.6%,2.8%和7.7%,小麦-玉米15N利用率显著大于苜蓿、黑杨和鸭茅,但与苜蓿-无芒雀麦无显著性差异。两年15N总利用率对应为30.2%,23.4%,25.6%,12.3%和11.4%,苜蓿-无芒雀麦显著高于其他处理,苜蓿和小麦-玉米显著高于鸭茅和黑杨。两年连作对标记15N利用率最大的是牧草间作,作物轮作及苜蓿连作对底土硝态氮也有较高量的吸收,而林木(黑杨)则较差。2硝态氮在土壤中移动性强,其空间有效性与作物根系的发育和分布关系密切。本试验研究发现,标记层区域作物的根长密度与作物对该区域的土壤标记硝态氮的利用率有很好的相关性。3在微区常规水肥管理条件下,一季后,鸭茅、黑杨15NO-3-N明显下移至130cm;苜蓿-无芒雀麦、苜蓿和春玉米未发生强淋洗,仅扩散20cm左右。连作两年,标记氮向下运移较向上强,鸭茅最为强烈(下移超过110cm)。结果表明可以利用牧草间作、作物轮作及苜蓿连作避免硝态氮进一步向深层迁移累积乃至向浅层地下水迁移。4硝态氮高累积剖面植物原位修复试验结果显示,连续种植两年总生物量黑杨、小麦-玉米、苇状羊茅、苜蓿-无芒雀麦和苜蓿分别为107.3,54.1,46.7 ,44.7和36.2kg/plot,黑杨显著高于其他处理,小麦-玉米显著高于苜蓿,三种牧草间无显著性差异。两年累计吸氮量对应为1053.4,595.4,902.3,854.3和826.1 g/plot;黑杨吸氮量显著高于其他处理,三种牧草之间没有明显差异,但显著高于小麦-玉米,在种植第二年吸氮量显著增加。本试验结果说明种植林木及牧草可以获得较高的生物量及吸氮量,牧草对土壤氮素吸收利用随种植年限而递增。5不同植物种类及土地利用方式对土壤剖面硝态氮分布的影响有差异,土层中硝态氮在一季后,0~100cm均有所降低,生草休闲和苇状羊茅消减能力较强;100~180cm(除苇状羊茅外)均高于种植前,说明种植当季有硝态氮淋洗。第二季后,苇状羊茅土壤剖面累积氮的表观损失量最高, 0~200cm土层硝态氮含量均低于5mg/kg,显著低于生草休闲和黑杨(0~20cm例外),黑杨有较强淋洗;苜蓿第二季较第一季对剖面硝态氮消减显著。6在通体高量积累硝态氮的土壤上,可以通过苇状羊茅、苜蓿-无芒雀麦及自然生草休闲的土地管理方式,实现土壤剖面硝态氮含量快速消减,但是自然生草仅在第一季效果较好。在必须考虑收获物经济利用条件下,故苇状羊茅和苜蓿-无芒雀麦为较优的选择,苜蓿在相对长期的修复中具有优势。更多还原

【Abstract】 Nitrogen is the tremendous power of increaseing production, but after a long-term some farmers had unreasonably inputed application of nitrogen fertilizer. That would lead to accumulate a large amount of nitrate in soil,and that is a serious threat to groundwater. Some people has focus on the issue that how to solve the high accumulative nitrate of subsoil. This study separately set up the field micro-plot experiments by technique of external injection of labeled 15NO3- -N and the field plot of in-situ testing about the nitrate-nitrogen accumulation to investigate of the behavior of residue nitrate and its utilization by the different roots plants and planting patterns in agro-ecosystem , and main conclusions as following:(1) Under conventional field management condition,about 15N injection micro-plot experiments, in the first season ,the recovery of labeled of 15NO3--N by alfalfa- bromus inermis intercropping,alfalfa,spring maize,cocksfoot and black poplar were 18.4%, 14.5%, 11.0%, 9.5% and 7.0% respectively. The recovery of labeled of 15NO3--N by alfalfa - bromus inermis intercropping was significantly higher than that by corn, black poplar and cocksfoot; and corn was significantly higher than that by cocksfoot and black poplar. The second season, the recovery of labeled of 15NO3--N by alfalfa- bromus inermis intercropping,alfalfa,spring maize, cocksfoot and black poplar were 11.8 %, 8.9%, 14.6%, 2.8% and 7.7% respectively. Furthermore, the recovery of labeled of 15NO3--N by wheat-corn were significantly higher compared with alfalfa, black poplar and cocksfoot, but alfalfa - bromus inermis was no significant difference. In two years, the total 15N utilization rate of alfalfa- bromus inermis intercropping,alfalfa,spring maize, cocksfoot and black poplar were 30.2%, 23.4%, 25.6%, 12.3% and 11.4% respectively. Alfalfa - Bromus inermis’s 15N utilization rate were significantly higher than other treatments, 15N utilization rate of alfalfa and wheat - corn was significantly higher than cocksfoot and black poplar. In two years ,15N utilization rate of the forage intercropping systeme was the max-rate, wheat maize rotation system and continuous cropping alfalfa was the second rate, but the trees’s (black poplar) 15N utilization rate was mini-rate.(2)In the soil Nitrate-N transport had intimate correlation with crop root development and distribution. The pilot study found that in the labeled soil- region the density of crop’s root length and the utilization rate of the crop’s nitrate had good correlation.(3)Under the micro-conventional water management conditions,after the previous quarter,cocksfoot and black poplar about the 15NO3--N had significantly movement to 130 cm; Downward leaching of alfalfa - Bromus inermis, alfalfa and spring corn were weaker, only the spread of 20cm. In two years,the movement of the 15NO3--N was stronger downward than upward, and the strongest was cocksfoot (down more than 110cm). The results showed that the forage intercropping, crop rotation and cropping of alfalfa could be used to avoid downward leaching of the accumulation of NO3--N.(4) The results of in situ test showed that : in two years, the total biomass of black poplar, wheat - corn, fescue, alfalfa- bromus inermis intercropping and alfalfa were 107.3 kg/plot,54.1 kg/plot,46.7 kg/plot, 44.7 kg/plot and 36.2kg/plot respectively, and the total biomass of black poplar was significantly higher than other treatments, wheat - corn was significantly higher than the alfalfa,among total biomasses of the three forage plants were no significant difference.The total N uptake of black poplar, wheat - corn, fescue, alfalfa- bromus inermis intercropping and alfalfa were: 1053.4, 595.4,902.3,854.3 and 826.1 g / plot respectively,in two years. The N uptake of black poplar was significantly higher than other treatments;among total N uptakes the three forage plants, but they were significantly higher than wheat– corn’s, The test results indicated that planting trees and forage plants can be higher biomasses and N uptake, with the increaseing of cultivation period N uptaks of forage plants had increased production.(5) Different plant species and land uses were different their influences of nitrogen distribution on soil profile. After the fist term, in depth 0-100cm of the soil nitrogen was reduced,the catch grass and the fescue were strongerly. In depth 100-180cm of the soil (except fescue) were higher than the pre-cultivation ,which showed that had nitrate leaching in first season. The second season, in soil profile the apparent loss of nitrogen of the fescue was the highest In depth 0-200cm of the soil , NO3--N were lower than 5mg/kg, it was significantly lower than the catch grass and the fescue (except in depth 0-20cm),The NO3--N of the black poplar was strongly leaching; nitrate of the alfalfa was reducted on the section season more then the first.(6) In the high accumulate of nitrate-N of all soil layers, reducttion of the fescue, the alfalfa - bromus inermis and the catch grass was used to reducte nitrate-N that was effective of nitrate-N, in the soil.But the catch grass was used to reducted nitrate-N that was good only in the first season. Under the condiction of the economical and effective way , the fescue and alfalfa - Bromus inermis were better in effectiveness of nitrate-N;and in the long-term the alfalfa was showed better。更多还原