【作者】 范庆锋；

【导师】 张玉龙；

【作者基本信息】 沈阳农业大学 ， 土壤学， 2009， 博士

【摘要】 保护地集约化栽培，复种指数高、大量施用化肥，加上缺少雨水淋洗、温度高等特殊环室内境条件，致使保护地使用若干年后，酸化、次生盐渍化、养分不平衡等诸多土壤退化问题随之产生。本文选择辽宁地区典型保护地作为研究对象，自辽宁西部的朝阳市、东部的丹东市和清源县、北部的铁岭市、中部的沈阳市东陵区和于洪区，采集不同类型、不用利用年限和不同深度层次的保护地土壤样品，采用室内分析化验和数理统计分析的方法，从土壤pH的地区分布及剖面分异、土壤活性酸度和潜在酸度、有机质含量及盐分含量及土壤离子组成等方面，对保护地土壤酸化的特征、原因、过程、机理进行了较为系统地研究，探讨了保护地土壤盐分积累及其组成变化与土壤酸化的关系。1．保护地土壤酸度现状按地区分类辽宁地区保护地土壤pH值高低排列顺序为：朝阳地区＞清源地区＞铁岭地区＞丹东地区＞沈阳东陵地区＞沈阳于洪地区。就同一地区土壤而言，丹东地区保护地土壤pH值随着由露地改为保护地后使用年限的增长而上升，其它地区保护地土壤pH则随着改为保护地使用年限增长而下降，即表现出酸化趋势，且几乎每一地区均有pH值小于5.50的土壤样品出现。显然这与改作保护地前当地土壤pH有关。用作保护地前中性和碱性土壤pH下降，而酸性土壤pH值上升。就同一地点、不同深度层次土壤而言，朝阳、铁岭、沈阳东陵和于洪地区保护地土壤pH值均呈现0～20cm土层＜20～40cm土层＜40～60cm土层＜60～80cm土层的分布规律。表层土壤（0～20cm）的pH值要远远低于其下各层次土壤；20cm以下各层次间土壤pH值的差异较小，至80cm深处已经近露地土壤pH值。而丹东、清源两地保护地0～80cm各土层土壤的pH值则表现为表层高于下层、即随着土层深度的增加其pH值逐渐降低的趋势。就同一地点、同一深度层次、不用种植年限的土壤而言，随着种植年限的增加，保护地土壤的pH值是持续下降的，但是在前1～4年左右下降速度缓慢，甚至有所上升；其后随着保护地种植年限的延长，pH值下降速度加快。2．保护地土壤酸化特征露地改为保护地栽培蔬菜后，土壤活性酸、交换性酸（EA）、非交换性酸（NEA）含量和交换性盐基（EB）总量、阳离子交换量（CEC）明显增加，且表层土壤增加趋势比下层明显，但盐基饱和度（BS）下降。土壤pH与EA、NEA呈极显著负相关关系，与EB呈极显著正相关关系；统计分析结果表明，土壤pH的变化主要取决与EA，而受NEA和EB的影响相对较小，土壤NEA含量较露地明显增加且一般都大于EA。EA总量不同，土壤中交换性H⁺、Al³⁺的相对比例随之变化；在EA＜0.75cmol kg^-1时以交换性H⁺占优势，而当EA＞0.75cmol kg^-1时则以交换性Al³⁺为主。保护地土壤CEC、土壤NEA与土壤有机质含量均呈极显著正相关关系。保护地上层和下层土壤中交换性盐基总量（EB）、交换性K⁺、交换性Mg²⁺、交换性Na⁺含量均高于露地相应层次的土壤，而交换性Ca²⁺含量与露地比较则表现出减少的趋势，但Ca²⁺在交换性盐基中仍占优势地位；交换性Ca、Mg、K、Na又与水溶性Ca、Mg、K、Na呈极显著正相关关系。保护地土壤pH与BS、特别是Ca²⁺饱和度呈显著正相关关系。与露地土壤相比，保护地土壤盐基饱和度BS和Ca²⁺饱和度下降是导致土壤pH降低的重要因素。3．保护地土壤酸缓冲性能作为保护地的种植年限越长，土壤pH值越低，土壤酸害容量（达到植物受害pH值所需要的酸）越小；越容易对作物产生酸害。不同种植年限保护地土壤和露地土壤的酸缓冲性能曲线相似，但斜率各不相同。露地土壤pH酸缓冲性能曲线斜率绝对值最大，加入等量酸后pH下降幅度最大，即土壤酸害强度（土壤对酸的承受能力）越小；而作为保护地种植年限越久，酸缓冲性能曲线斜率绝对值最小，加入等量酸后土壤pH下降的越慢，土壤酸害强度越大。土壤酸害强度与有机质含量及阳离子交换量均呈极显著的正相关关系。4．保护地土壤酸化的影响因素（1）土壤有机质含量。土壤有机质含量较露地土壤大幅度提高是影响保护地土壤酸化的重要因素之一；土壤有机质含量增加，使保护地土壤的非交换性酸含量提高、酸缓冲能力上升。（2）土壤含盐量。保护地土壤pH值与含盐量呈极显著对数负相关关系，即土壤pH值随着土壤含盐量的增加而降低。保护地土壤的盐分含量随着作为保护地种植年限的延长而不断增多，由露地改为保护地10年左右供试表层土壤的平均含盐量从0.29g kg^-1上升至1.56g kg^-1，EC值达到0.53mS cm^-1，已超过作物的生育障碍临界点(EC＞0.50mS cm^-1)。盐分含量随土层深度增加而降低。（3）盐分离子组成。露地改为保护地栽培蔬菜后，土壤盐分含量增加，其中NO₃^-、SO₄^2-、Cl^-和Ca²⁺、Mg²⁺、Na⁺、K⁺均有不同程度的增加，而HCO₃^-则减少。阴离子以NO₃^-和SO₄^2-为主，阳离子以K⁺和Ca²⁺为主。供试表层土壤有的NO₃^-含量已高达0.66g kg^-1，是露地土壤的29倍。而阳离子以K⁺增加最为显著。统计分析结果表明，NO₃^-、SO₄^2-等强酸性阴离子特别是NO₃^-含量在全盐含量中所占比例上升，HCO₃^-、Na⁺等盐基离子在全盐中的相对比例下降是导致土壤pH值下降的重要因素。综上所述，特殊的保护地室内水热条件、过量施肥和连年高强度利用，致使土壤有机质含量积累、土壤盐分含量上升和盐分离子组成及其比例改变，构成了新的土壤酸平衡体系；硝酸根、硫酸根和钙、钾等阳离子的增加及其比例改变，是导致土壤pH上升或者下降的直接原因。为了实现作物高产、优质和防治保护地土壤退化，应控制化肥和有机肥用量，合理地选择土壤水分管理技术，并辅以轮作、揭棚淋洗等措施，则是十分重要和必要的。更多还原

【Abstract】 Soil acidification, soil salinization and nutrient imbalance were serious in protected fieldbecause of the intensive cultivation, higher multiple cropping index, fertilizer managementmeasures unreasonably and the lack of rain, which not only affected the sustainabledevelopment of food production, but also had a series of agricultural product quality securityand environmental protection problems. This paper used typical soil of protected field in theliaoning region to study the characteristic, reason, process, mechanism of soil acidificationand to explore the relation between soil salinity accumulating and pH with the help of indoorculture and mathematical analysis. The results were showed as follows:1. The present condition analysis of soil acidification in typical protected field inLiaoning.The areas should be arranged from high to low, according to their soil pH in Liaoningprotected field, as follows: Chaoyang > Qingyuan > Tieling > Dandong > Dongling > Yuhong.At the present time, the soil pH sharply decreased after the field began vegetable cultivationunder protection in most of Liaoning District （except Dandong）, and the sampling point that islesser than pH 5.50 consist in most of Liaoning district.The soil pH shows the trend of 0～20cm soil layer<20～40cm soil layer <40～60cm soillayer <60～80cm soil layer in protected field in Chaoyang, Tieling, Dongling and Yuhong.The soil pH increased and closed to open field with soil depth increasing, and topsoil（0～20cm） pH was far below the under layer, Differences among other soil layers were small. Butthe pH of topsoil layer higher than other soil layers in protected field in Dandong andQingyuan. That is to say, the soil pH declined with soil depth increasing, and that’s becausethere were related to field manage measures in protected field, geographical location and soiltexture.With replanting time prolonging, the soil pH was continuing decline in protected field.But the soil pH declined at a slow pace even increased in the first 1～4 years, and withreplanting time prolonging, the soil pH declined at a quick pace. With replanting timeprolonging, the soil pH was continuing decline in protected field in general.2. Acidity characteristics of soils in protected fieldsThe content of active acidity increased obviously after the field began vegetablecultivation under protection. Soil acidification displayed a clear rising trend in topsoil thansubsoil. EA, NEA, and EB, in various layers of the soils in the protected fields were muchhigher than those in the open fields, Soil pH was in significant negative correlation with EAand NEA, but in significant positive correlation with EB, Related coefficient and partial regression coefficient of regression equation showd that: Soil pH was determined mainly byEA, while NEA and EB had less impact on that.Exchangeable H⁺ were predominant when the EA<0.75cmol kg^-1, and exchangeable Al³⁺were predominant when the EA>0.75cmol kg^-1 The proportion of exchangeable Al³⁺increased with increasing exchangeable acid, while decreased with increasing OM. And, theproportion of H⁺ in exchangeable acid showed a reverse trend. The content of NEA increasedobviously after the field began vegetable cultivation under protection. The content of NEAwere usually higher than EA. Soil NEA was in significant positive correlation with OM.OM and CEC of the soils in the protected fields were much higher than those in the openfields. Soil CEC was in significant positive correlation with OM, it indicated that with thecontent of OM increasing, the soil CEC was continuing increase in protected field.Exchangeable EB, exchangeable K⁺, exchangeable Mg²⁺ and Exchangeable Na⁺ invarious layers of the soils in the protected fields were much higher than those in the openfields, whereas exchangeable Ca²⁺ in various layers of the soils in the protected fields weremuch lower than those in the open fields, but the difference was not significant. ExchangeableCa²⁺ was predominant in exchangeable EB. Exchangeable K⁺ of the soils has been a dramaticrise in the protected fields, which was the main characteristic of exchangeable EBcomposition variation. Soil Water-solubility Ca, Mg, K, Na were in significant correlationwith exchangeable Ca, Mg, K, Na. Therefore, soil water-solubility EB composition variationwas the main influential factor of the exchangeable EB composition variation.PA and total exchangeable EB of the soils in the protected fields were much higher thanthose in the open fields, but the base saturation （BS%）, the saturation of exchangeable Ca²⁺decreased significantly because of the increase of CEC, There is a significant positivecorrelation between the soil pH and the BS （%）, which is mainly restrained by the dominantexchangeable base Ca²⁺. Therefore, It was an important factor that the BS（%）, especially thesaturation of exchangeable Ca²⁺ decreased which caused soil acidification.3. Effects of protected field vegetable cultivation on soil salinity accumulating and pHThe salinity content and EC value of the soils in the protected fields were much higherthan those in the corresponding open fields. The average of the salinity content was 0.29g kg^-1in open field soil. With replanting time prolonging, the salinity content was continuingincrease in protected field, The average of the salinity content had reached 1.56g kg^-1 after thefield began vegetable cultivation under protection for 10 years. Corresponding EC hadexceeded the scope of that was 0.53mS/cm.The salinity content of 0～80cm soil layer in the protected fields were much higher thanthose in the corresponding open fields. The salinity content declined with soil depth increasing. The salinity content of topsoil was far above the under layer. The salt movingdownwards to the bottom soil and salt accumulating upwards to the topsoil were very obviousin the protected field soils.Apart from HCO₃^-, the content of NO₃^-, SO₄^2-, Cl^-, Ca²⁺, Mg²⁺, K⁺, Na⁺ increasedsignificantly in protected field. Anions are mainly NO₃^- and SO₄^2-, Cations are mainly K⁺ andCa²⁺. The content of NO₃^- may reach 0.66g kg^-1, that was 29 times than in open field.There is a significant logarithmic negative correlation between the soil pH and thesalinity content, that is to say, the soil pH declined with soil salinity content increasing.Correlation analysis, path analysis and stepwise regression results suggested that theproportion of strongly acidic Anions NO₃^-, SO₄^2-, especially NO₃^-, to total salts decreasedwhich caused soil acidification. And it was an important factor that the proportion of HCO₃^-,Ca²⁺ to total salts decreased which caused soil acidification.4. Studies on acidic buffer capacity in protected field soilThe soil pH declined with acid accession in protected fields under different plantingyears. But the rate of pH declined in the shape of "L". The rate of pH declined quickly inopen fields, and the rate of pH declined quickly. The longer the planting years in protectedfield, the slower to the rate of pH declining. When acid accession had once been accumulatedto a certain degree, soil pH in open fields was already below in protected fields.With replanting time prolonging, the soil acid-damage capacity was continuing decreasein protected field, that is to say, the acid bearing capacity of soil was keep decreasing. That’sbecause there were related to soil pH. The higher the soil pH, the more acid to need to reachthe point of crops injured. Therefore, the longer the planting years in protected field, the lowerthe pH and soil acid-damage capacity, the less content of acid to reach the point of cropsinjured, the easier injured.With replanting time prolonging, the soil acid-damage intensity was continuing increasein protected field, that is to say, in the case of equal acid joining, the longer the planting yearsin protected field, the smaller of the degree to which soil pH declined. That’s because therewere related to soil OM and CEC. There is a significant positive correlation between soilacid-damage intensity and the content of OM and CEC. That is to say, the higher the contentof OM and CEC, the stronger the ability of the soil to resist acid, it would slow down soilacidification. There were some differences between soil acid-damage capacity and soilacid-damage intensity, Soil acid-damage intensity can better reflect that the soil is sensitive toacid than soil acid-damage capacity.更多还原