再生水地下滴灌对土壤酶活性和大肠杆菌（Escherichia coli）迁移的影响

发布时间：2018-09-18 09:34

【摘要】：滴灌是应用再生水最适宜的灌溉方式,能够避免直接接触污染和减少污染物随地表径流迁移,但是再生水中含有相对较高的盐分、养分、溶解性有机质和病原体等物质,且再生水滴灌可能增加根区土壤盐分和养分含量以及病原体浓度,影响根区土壤养分转化和生物活性,进而增加养分淋失、病原体淋溶污染地下水的风险。因此,研究再生水滴灌条件下灌水量和滴灌带埋深对土壤酶活性、大肠杆菌-Escherichia coli(E.coli)分布和水氮淋失的影响对再生水安全高效灌溉具有重要的理论和实践指导意义。本文以玉米(Zea mays L.)为研究对象,于2014和2015年在华北平原半湿润地区(北京大兴)开展再生水地下滴灌大田玉米试验。试验因素包括灌水量、滴灌带埋深和灌溉水质3个因素。其中,灌水量按作物需水量(ETC)的70%(I1)、100%(I2)和130%(I3)设置3个水平;滴灌带埋深设为0 cm(D1)、15 cm(D2)和30 cm(D3)3个水平;此外,将地下水灌溉设置为对照处理(2014年地下水对照灌水量为12;2015年地下水对照灌水量为I3),对照处理滴灌带埋深分别为0、15和30 cm,记为C1、C2和C3。玉米生育期内监测了土壤酶活性(碱性磷酸酶、脲酶和蔗糖酶)、E.coli分布、水氮动态、NO33--N淋失特征、土壤电导率(ECb)和化学性质,并在关键生育阶段测定了植株株高、叶面积指数(LAI)和叶、茎、籽粒干物质质量以及吸氮量,分析了滴灌带埋深、灌水量和灌溉水质对土壤酶活性、E.coli分布与运移、土壤水氮分布与淋失、土壤盐分、玉米生长和产量的影响。为了更系统地定量评价施肥制度对再生水亏缺灌溉条件下浅滴灌带埋深处理(I1D2)硝态氮淋失的影响,基于HYDRUS-2D软件构建了地下滴灌水氮运移模型,并模拟分析了施氮量对再生水亏缺灌溉条件下浅滴灌带埋深处理硝态氮淋失的影响。主要结论如下:(1)再生水地下滴灌条件下,0～20 cm深度土壤含水率随灌水量增加而显著增加,随滴灌带埋深增加而显著减小;较大灌水量和滴灌带埋深均会导致NO_3~--N向下层土壤运移,增大NO_3~--N淋失风险。与地下水灌溉相比,再生水灌溉增加了土壤NO_3~-N含量而降低了土壤NH4+-N含量。灌溉后表层土壤ECb增幅以较低滴灌带埋深处理较高,而随着土壤深度增加,ECb增幅随滴灌带埋深呈增加趋势。两年试验中,再生水灌溉明显提高了 0～50 cm深度土壤ECb,但是不会导致土壤盐渍化。(2)再生水地面灌和滴灌后碱性磷酸酶、脲酶和蔗糖酶活性在土壤剖面均呈层状分布。较小的滴灌带埋深明显提高了表层土壤酶活性,较大的滴灌带埋深显著促进了深层土壤酶活性;与滴灌带埋深相比,灌水量对土壤酶活性的影响随土壤深度、生育阶段和酶活性类型而变化。相关分析结果表明:灌溉处理前后碱性磷酸酶、脲酶和蔗糖酶活性与土壤有机质、全氮、全磷和pH显著相关,不同类型酶活性对灌溉施肥管理响应一致;脲酶活性在玉米生育前期促进尿素水解和氮素矿化,后期促进氮素吸收和生物固持。与地下水滴灌相似,再生水地下滴灌提高了根区土壤酶活性,没有干扰和改变土壤C、N、P养分转化,不会对土壤肥力水平造成负面影响。(3)再生水地下滴灌不会导致玉米生育期E.coli在土壤中累积,E.coli不会随深层渗漏进入深层土壤。水分深层渗漏主要发生在降雨较大而作物耗水量较小的生育初期和末期。滴灌条件下较大的灌水量和滴灌带埋深均会增加深层渗漏风险和导致土壤溶液中较高的NO_3~-N浓度;玉米生育期累积NO_3~-N淋失量随滴灌带埋深增加而显著增加。与地下水滴灌相比,再生水滴灌明显增加了 NO_3~--N淋失量,2014和2015年平均增加幅度分别为65%和84%。(4)灌水量和滴灌带埋深均未显著影响玉米产量及其构成要素。与地下水滴灌相比,再生水滴灌未对玉米株高、LAI、地上部分干物质质量及吸氮量、产量及其构成要素和品质造成显著差异;同时,再生水滴灌未造成玉米籽粒E.coli污染。考虑节水、玉米产量和根区水氮淋失,华北平原半湿润地区滴灌条件下玉米生育期内采用灌水量为70%ETC较为适宜。(5)基于HYDRUS-2D软件建立了地下滴灌线源土壤水分、NO_3~--N和NH4+-N运移模型,评估了施氮量及其分配对NO_3~--N淋失的影响。模拟结果表明:玉米生育期累积NO_3~--N淋失量随施氮量增加而增加。综上所述,滴灌带埋深15 cm的地下滴灌结合70%ETC灌溉能够提高作物根区土壤酶活性,避免再生水直接接触污染和E.coli在土壤中累积,同时降低水氮淋失,并维持较高的玉米产量,是华北平原半湿润地区大田玉米较合适的再生水灌溉管理方式。
[Abstract]:Drip irrigation is the most suitable irrigation method for reclaimed water, which can avoid direct contact with pollution and reduce pollutant migration with surface runoff. However, reclaimed water contains relatively high salinity, nutrients, dissolved organic matter and pathogens, and reclaimed water drip irrigation may increase soil salinity and nutrient content and pathogen concentration in root zone. Therefore, it is necessary to study the effects of irrigation quantity and buried depth of drip irrigation zone on soil enzyme activity, distribution of E. coli and leaching of water and nitrogen on safe and efficient irrigation of reclaimed water. In this paper, a field experiment of reclaimed water subsurface drip irrigation on Maize (Zea mays L.) was carried out in the semi-humid area of North China Plain (Daxing, Beijing) in 2014 and 2015. The experimental factors include irrigation quantity, buried depth of drip irrigation zone and irrigation water quality. Among them, irrigation quantity is based on crop water requirement (ETC). Three levels were set up for 70% (I1), 100% (I2) and 130% (I3); the buried depth of drip irrigation belt was 0 cm (D1), 15 cm (D2) and 30 cm (D3); in addition, groundwater irrigation was set as the control treatment (groundwater control irrigation in 2014 was 12; groundwater control irrigation in 2015 was I3), and the buried depth of drip irrigation belt was 0, 15 and 30 cm respectively, which was recorded as C1, C2 and C3. Soil enzyme activities (alkaline phosphatase, urease and sucrase), E.coli distribution, water and nitrogen dynamics, NO33-N leaching characteristics, soil electrical conductivity (ECb) and chemical properties were monitored during rice growth period. Plant height, leaf area index (LAI), leaf, stem and grain dry matter quality and nitrogen uptake were measured at key growth stages. Effects of irrigation quantity and irrigation water quality on soil enzyme activity, E.coli distribution and movement, soil water and nitrogen distribution and leaching, soil salinity, maize growth and yield were studied. The main conclusions are as follows: (1) Under the condition of subsurface drip irrigation with reclaimed water, the soil moisture content at 0-20 cm depth increases significantly with the increase of irrigation amount, and decreases significantly with the increase of the depth of the drip irrigation zone. Compared with groundwater irrigation, reclaimed water irrigation increased the content of soil NO_3~-N and decreased the content of soil NH4 +-N. After irrigation, the increase of ECb in surface soil was higher at lower depth of drip irrigation, but with the increase of soil depth, ECb increased. In the two-year experiment, the soil ECb of 0-50 cm depth was significantly increased by reclaimed water irrigation, but soil salinization was not observed. (2) Alkaline phosphatase, urease and invertase activities were stratified in soil profiles after surface and drip irrigation. The results showed that the soil enzyme activities were significantly promoted by the deeper buried depth of drip irrigation zone, and the effects of irrigation amount on soil enzyme activities varied with soil depth, growth stage and enzyme activity types. Nitrogen, total phosphorus and pH were significantly correlated, and the responses of different enzyme activities to irrigation and fertilization management were consistent. Urease activity promoted urea hydrolysis and nitrogen mineralization in early growth stage, and nitrogen absorption and biological fixation in late growth stage of maize. Nutrient transformation had no negative effect on soil fertility. (3) Subsurface drip irrigation with reclaimed water did not cause E. coli accumulation in soil during maize growth period, and E. coli did not enter deep soil with deep leakage. Compared with drip irrigation, drip irrigation with reclaimed water significantly increased the leaching loss of NO_3-N, with an average increase of 65% in 2014 and 2015, respectively. (4) Compared with drip irrigation, there was no significant difference in plant height, LAI, aboveground dry matter quality, nitrogen uptake, yield, components and quality of maize, and there was no significant difference in E. coli pollution. Considering water saving, maize yield and root water and nitrogen leaching loss, 70% ETC was more suitable for maize growth period under drip irrigation in semi-humid area of North China Plain. (5) Based on HYDRUS-2D software, soil moisture, NO_3~--N and NH4 + - N transport models of subsurface drip irrigation line source were established, and the effects of nitrogen application and its distribution on NO_3~--N leaching were evaluated. The results showed that the accumulation of NO_3~--N leaching increased with the increase of nitrogen application. In conclusion, the combination of subsurface drip irrigation with 70% ETC irrigation at a depth of 15 cm in drip irrigation zone could improve soil enzyme activity in crop root zone, avoid the direct contact of reclaimed water with pollution and the accumulation of E.coli in soil, reduce water and nitrogen leaching, and maintain higher maize yield. Yield is a suitable management mode of reclaimed water for field corn in semi humid area of North China Plain.
【学位授予单位】：中国水利水电科学研究院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S275.6;S154

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