【作者】 陈竹君；

【导师】 王益权；

【作者基本信息】 西北农林科技大学 ， 土壤学， 2008， 博士

【摘要】 近20年来，日光温室在我国的发展十分迅速，已成为我国设施农业产业的主体。生产中十分重视肥料的施用，导致过量施肥、养分比例失调等问题相当普遍，由此产生了一系列不良后果，包括土壤盐分累积、养分利用率低、土壤质量退化及环境风险增加、有害物质积累、生物多样性衰退等，严重影响了日光温室产业的可持续发展。这些问题已引起不少研究者的重视，但已有研究更多的集中在温室土壤盐分累积及合理施肥等方面。土-液界面离子交换作用是陆地生态系统固相与液相物质交换的主要方式，不仅与土壤养分的保持和供应，而且与养分在土壤中的迁移和转化有紧密的联系。日光温室大量的养分投入，无疑会频繁地影响土壤固-液界面离子交换过程进行的方向和程度。日光温室栽培下出现的上述问题，实际上是过量施肥影响土-液界面离子交换后的表象。目前，关于日光温室这一高强度集约栽培方式下土壤养分累积导致的土壤离子组成变异而产生的土壤不健康问题以及土壤固-液相界面离子交换作用特性变化等对土壤质量和生态环境风险影响的研究相对较少。本文以陕西省关中地区日光温室为研究对象，采用常规化学分析方法、模拟试验与物理化学方法相结合，研究了日光温室栽培下不同土壤养分累积及交换性养分(K⁺、Ca²⁺、Mg²⁺等)含量及比例的变化，不同氮肥品种（尿素、碳酸氢铵、硫酸铵）及磷钾肥施用对日光温室土壤溶液电导率（EC）和不同离子组成及比例的影响，外源不同K⁺、Ca²⁺、Mg²⁺比例和浓度对土壤离子吸附交换特性的效应，以及温室栽培对土壤K-Mg、K-Ca交换选择系数、自由能变化等的影响。旨在揭示日光温室栽培土壤固-液相离子组成、比例、盐分累积和离子交换特性的演变趋势和机理，为有效评价土壤固-液界面养分离子交换特性与土壤养分供应的关系，针对性地调节土液界面养分离子的平衡状况，协调作物养分供应，维持和提高土壤质量和降低生态风险提供理论依据。研究取得了以下主要结论：（1）采用高速离心法提取土壤溶液方法，比较了温室栽培土壤和大田土壤溶液离子含量及比例差异后发现，温室栽培土壤溶液电导率（EC）、K⁺、Na⁺、Ca²⁺、Mg²⁺、NO₃^-离子浓度以及K⁺／Ca²⁺、K^-／Mg²⁺比例分别为大田土壤的2．5、95．0、16．6、1．9、3．2、4．0、31和39倍，表明日光温室土壤盐分累积及养分比例失调问题突出。（2）与大田土壤相比，日光温室土壤交换性K⁺含量显著增加，土壤交换性Ca²⁺含量无明显差异，土壤交换性Mg²⁺的含量及其离子饱和度有所提高，而日光温室土壤钙饱和度、Ca／K和Mg／K均明显低于大田土壤，这与日光温室栽培下大量施用钾肥有关。研究地区日光温室栽培番茄频频出现缺镁问题。研究表明，日光温室土壤交换性Mg²⁺含量及其离子饱和度与大田土壤相比并不低，且有所提高，而Mg／K均明显低于大田土壤。由于K⁺与Mg²⁺之间又存在明显的拮抗作用，再加上番茄是需镁较多的作物，因此，Mg／K比例失调可能是石灰性土壤地区日光温室栽培番茄频频出现缺镁的主要原因。（3）土培模拟与高速离心法直接提取土壤溶液相结合，研究了不同氮肥品种及用量对日光温室土壤溶液离子组成、比例的影响。结果表明，施用不同氮肥品种（尿素、碳酸氢铵和硫酸铵）对土壤溶液EC的影响有所差异，培养起始时硫酸铵对土壤溶液EC明显大于尿素和碳酸氢铵处理，之后不同氮肥品种对土壤溶液EC影响的差异变小。与氮肥种类相比，其施用量对土壤溶液EC更为明显，随着氮肥施用量的增加日光温室土壤培养过程中土壤溶液EC显著增加，说明氮肥施用量与土壤盐分累积具有十分密切的关系。同时，增施氮肥还促使土壤固相等量的将Ca²⁺、Mg²⁺、K⁺、Na⁺等离子解离进入土壤溶液中，从而造成盐分累积状况加剧。（4）采用土培模拟与高速离心法直接提取土壤溶液相结合，研究了磷钾肥不同配比对日光温室土壤溶液离子组成、比例的影响。结果表明，增加磷施用量，显著降低土壤溶液EC和Ca²⁺、Mg²⁺离子含量，对土壤溶液K⁺、NO₃^--N和NH₄⁺-N离子浓度均无显著影响。增施钾肥，土壤溶液EC和K⁺、Na⁺、Ca²⁺、Mg²⁺、K⁺／Ca²⁺、K⁺／Mg²⁺比例均呈增加趋势。依据土壤特性，合理施用有机肥、氮、磷、钾肥，是防止温室栽培土壤盐分累积、阳离子养分比例失调，保持土壤结构的有效途径。（5）日光温室栽培土壤钾素Q／I曲线及参数与大田土壤明显不同，温室栽培下塿土和潮土土壤钾素活度比（AR₀）较相应大田土壤分别提高了14．8和6．9倍。土壤对外源钾的缓冲能力下降；从K⁺和Ca²⁺+Mg²⁺的交换自由能看，温室土壤存在因钾素过多可能引发钙、镁缺乏的风险。（6）塿土和潮土无论温室还是大田土壤K-Mg、K-Ca交换等温线均属“S”型曲线。随固相吸附K饱和度的增加，选择系数均呈指数趋势降低。K-Mg、K-Ca交换等温线与非选择交换等温线比较结果和选择系数变化均表明，土壤对K⁺离子的吸附选择均有转折点，对于K-Mg交换，大田塿土、温室塿土、大田潮土和温室潮土K⁺离子吸附选择转折点对应的交换性K⁺含量分别为1385．5、1355．5、1007．1和1106．3 mg／kg，对于K-Ca交换，K⁺离子吸附选择转折点对应的交换性K⁺含量分别为580．3、575．6、415．4和355．1mg／kg时，当土壤交换性K⁺含量分别小于转折点交换性K⁺含量时，K⁺可以自发代换Ca²⁺、Mg²⁺离子被土壤胶体吸附。更多还原

【Abstract】 The cultivating areas of sunlight greenhouse in China during the past 20 years haveincreased rapidly,and it has become one of main types of protected cultivation in China.Mostfarmers have paid a great attention to the application of fertilizer in sunlight greenhouses.Excessive application of fertilizers is very common in most regions.It resulted in a series ofproblems,including nutrient imbalances,over-accumulation of salts and harmful substancesin soils,low use efficiency of fertilizers,degradation of soil quality.These problems havelimited the sustainable development of sunlight greenhouse in China.Although someresearchers had dealt with these problems,most of them have concentrated on saltaccumulation in soil and the optimum application of fertilizers in greenhouses.Ion exchangein soil and solution interface is one of major exchange way of substances between soilparticles and growing plant roots in terrestrial ecosystem.Ion exchange in soil has a closerelationship not only with the supply of nutrient in soil,but nutrient movement andtransformations in soils.Obviously,the excessive application of fertilizers in sunlightgreenhouse will affect the ion exchange balances in the soils.The problems taken place insunlight greenhouse is the phenomena of ion imbalances in soil.However,there are limitedstudies about the effect of sunlight greenhouse cultivation on nutrient accumulation and ionexchanging properties in soils.Therefore,we carried out this research in the sunlight greenhouse bases located inGuanzhong plain,Shaanxi Province with the different methods（chemical analysis,incubationmethod,and physi-chemical methods）to study the effects of sunlight greenhouse cultivationon the nutrient accumulation and ion balances(K⁺,Ca²⁺,Mg²⁺)in the soils,and effects ofaddition of different forms of nitrogen fertilizers（urea,ammonium carbonate,and ammoniumsulfate）and phosphorus and potassium fertilizers on the electric conductivity（EC）and ioncompositions and ratios of soil solution,and the effects of different concentrations and ratiosof K⁺ and Mg²⁺ions on the adsorptions of K⁺,Ca²⁺and Mg²⁺ions by the soils.The majorconclusions were as follows:（1）The EC and concentrations of K⁺,Na⁺,Ca²⁺,Mg²⁺,NO₃^-ions and ratios of K⁺/Ca²⁺, K⁺/ Mg²⁺in soil solution of greenhouse obtained with the centrifugation method withoutadditioin of fertilizer were 2.5,95.0,16.6,1.9,3.2,4.0,31 and 39 times of that in arable soil,respectively,indicating the serious accumulation and imbalances of ions in the sunlightgreenhouse soil in research regions.（2）Compared to the openland soils,the sunlight greenhouse cultivation significantlyincreased the contents of exchangable K⁺ and Mg²⁺ions in the soils,and had not significanton the content of exchangable Ca²⁺ions in the soils.On the contrary,the sunlight greenhousecultivation significantly decreased the saturation of Ca²⁺ions in soil colloids,and the ratioesof Ca/K and Mg/K in the soils.This is related to the excessive application of K fertilizers inthe sunlight greenhouses.Tomato deficient in magnesium usually occurs in some greenhousesin the research region.This could not be explained by the contents and saturation ofexchangable Mg²⁺ions in the soils,because of higher levels in greenhouse soil than that inopenland soil.The ratio of Mg/K in the greenhouse soils was lower than the openland soil.Imbalance of Mg/K in the greenhouse soils is considered as the major reasons for magnesiumdeficiency in tomato due to the antagonistic interaction between K⁺ and Mg²⁺ions and highneed of Mg²⁺ion by tomato.（3）Addition of different forms of nitrogen fertilizers only had some effects on the EC ofsoil solution in the first week of incubation,after that the differences among the differentforms of N fertilizers were not significant.The EC of soil solution was significantly increasedas the increasing of N application rate,indicating the high contribution of nitrogen rate to theaccumulation of salts in the soil.The nitrate concentration in soil solution was increased withthe rates of N fertilizer added and the incubation time.The application of N fertilizer alsoincreased the concentrations of K⁺,Na⁺,Ca²⁺and Mg²⁺in soil solution,especially theconcentration of Ca²⁺and Mg²⁺ions.More attention is need to pay to the effects of Napplication rates on the accumulation of salts in soil,and the leaching of K⁺,Na⁺,Ca²⁺andMg²⁺from soil solution.（4）The application of P and K fertilizers had different effects on ion composition of soilsolution.Addition of P fertilizer significantly decreased the EC and concentrations of Ca²⁺,Mg²⁺ions both in arable and greenhouse soils,its effect on concentrations of K⁺,NO₃^--N andNH₄⁺-N ions in the soils was not significant.As the increasing addition of K fertilizer,the ECand concentrations of K⁺,Na⁺,Ca²⁺,Mg²⁺ions and ratios of K⁺ / Ca²⁺,K⁺ / Mg²⁺in solutionsof arable and greenhouse soils increased.It is concluded that adquate application of Kfertilizer is important in preventing the excessive accumulations of salts,cation imbalancesand poor structure of greenhouse soils.（5）The activity ratios between K⁺,Ca²⁺,and Mg²⁺ions of two greenhouse soils used（i.e., Loess soil and fluvo-aquic soil）at the point where no change of exchangeable K⁺ takes place（AR₀）were about 14.8 and 6.9 higher than the corresponding open land soils,respectively.The buffer capacities of greenhouse soils to add K+ were lower than that of open land soil.The changes of Gibbs free energy of K⁺,Ca²⁺,and Mg²⁺exchange（△G）of greenhouse soilsindicated these soils had the potential deficiencies of Ca²⁺,and Mg²⁺induced by the excessiveapplication of potassium fertilizer.（6）Ion adsorption isotherm curves of K-Mg and K-Ca both in greenhouse and openlandsoils followd the S-shape curve.As the increasing of K⁺ ion saturation in soil particles,theselectivity coefficients of the K-Mg and K-Ca equilibria decreased.The selectivitycoefficients of the K-Mg and K-Ca of the preference and non-preference isotherms indicatedthat the soils used had a turn-point for selectively adsorbing K⁺ ions.For K-Mg equilibrium,the exchangeable K⁺ ions in soils corresponded for the turn-points for selectively adsorbingK⁺ ions were 1385.5,1355.5,1007.1 and 1106.3 mg/kg for the Loess soils in openland andgreenhouse,and the fluvo-aquic soil in openland and greenhouse,respectively;For K-Caequilibrium,the exchangeable K+ ions in soils corresponded for turn-points for selectivelyadsorbing K⁺ ions were 580.3,575.6,415.4 and 355.1 mg/kg for the Loess soils in openlandand greenhouse,and the fluvo-aquic soil in openland and greenhouse,respectively.When theconcentrations of exchangeable K+ ions in soils were lower than the correspondedexchangeable K⁺ ions at the turn-points,K⁺ ions could exchange the exchangeable Ca²⁺,andMg²⁺ions adsorbed by soil colloids.更多还原