不同灌溉方式对设施土壤酸化影响机制研究

Acidification is an important degradation process and the main characteristics of soil in greenhouse. When acidification reaches a certain level, plants will suffer toxic by aluminum, manganese and hydrogen, and nutrients availability will be changed and resulting in nutrient imbalances. Accordingly, crop productivity and soil quality will be decreased. Unlike exposed soil, soil acidification for greenhouse often happens simultaneously with salinization. Obviously, it relates to not only fertilization, but also closely to soil hydrothermal conditions such as irrigation. Recently, the effects of precipitation, fertilization and land utilization type on soil acidification have been reported. While the studies about the relationship between acidification and irrigation methods in greenhouse is limited. There are not deeply researches on the mechanism of soil acidification. Soils will be sampled from greenhouse with long-term irrigation experiment. The index changes of soil acidification will be compared among different irrigation methods by analyzing the relationship between soil pH, latent acid and exchangeable cations, base saturation and salt content. The influence mechanism of irrigation methods on soil acidification will be discussed on the basis of the relationship between soil acidification and salinization. The acidification characteristics caused by different irrigations will also be evaluated. These results will provide valuable theoretical basis and technology guide for soil water management in greenhouse.

酸化是设施土壤退化的重要过程和主要特征之一。土壤酸化至一定程度后，不仅导致铝、锰和氢对植物的毒害作用发生，也会使营养元素有效性改变、造成养分失衡，从而使作物减产、土壤资源质量下降。与露地土壤不同，设施土壤酸化往往与盐渍化同步发生；显然这既与施肥等因素有关、也与灌溉等土壤水热条件关系密切。目前，关于土壤酸化的研究多集中于降水、施肥、土地利用方式的影响上，即使设施土壤关于酸化与灌溉方式之间关系的研究也不多见，对设施土壤酸化机理缺乏深入的研究。本课题以长期定位灌溉试验设施土壤为供试材料，通过分析土壤pH、潜性酸与交换性阳离子、盐基饱和度、盐分含量等之间的关系，比较不同灌溉处理土壤酸化指标的剖面变化，在探讨土壤酸化与盐化之间关系的基础上阐释灌溉方式对土壤酸化的影响机制、对设施土壤酸化机理做出进一步解释，并对不同灌溉方式致酸特点做出评价，以期为设施蔬菜栽培进行合理的水分管理提供理论依据与技术指导。

酸化是设施土壤退化的主要问题之一。与露地土壤不同，设施土壤酸化往往与盐渍化同步发生，显然这既与施肥等因素有关、也与灌溉等土壤水热条件关系密切。本课题自长期定位灌溉试验设施地分层采集沟灌、滴灌、渗灌3种灌溉处理土壤样品，比较不同灌溉处理土壤酸化指标的剖面变化，分析土壤pH与潜性酸、交换性阳离子、盐基饱和度、盐分含量等之间的关系，在探讨土壤酸化与盐化之间关系的基础上阐释灌溉方式对土壤酸化的影响机制，并对不同灌溉方式致酸特点做出评价。结果表明：1）沟灌、滴灌、渗灌三种灌溉方式下土壤pH值均是表层最低，随着土壤层次的不断加深而逐渐升高，在0~30cm土层范围，土壤pH值均表现出滴灌高于沟灌和渗灌；各处理土壤交换性酸、非交换性酸含量随土层加深而降低，各灌溉处理间在0~30cm土层其含量差异显著，表现为渗灌>沟灌>滴灌。2）三种灌溉方式土壤有机质、阳离子交换量及盐基离子含量表层较高，不同灌溉方式间表层土壤有机质含量及阳离子交换量表现为渗灌高于沟灌，沟灌高于滴灌，土壤交换性盐基离子含量总体以渗灌处理最高。各灌溉方式0~60cm土层土壤盐基离子饱和度大小顺序均Ca2+>Mg2+>K+>Na+。Ca2+、Mg2+饱和度在0~30cm土层滴灌最高，30~60cm土层渗灌最高。K+饱和度总体以渗灌为高，沟灌居中，滴灌最低；土壤Ca/K、Mg/K比值总体以滴灌最高，沟灌次之、渗灌较小。3）三种灌溉方式土壤全盐含量、硝态氮均呈现出明显的表聚现象，0~20 cm土层范围内，滴灌处理硝态氮含量和全盐含量明显低于沟灌和渗灌处理。4）土壤pH与潜性酸、盐基离子组成及其饱和度、全盐含量和盐分离子组成关系密切。统计分析结果表明，土壤pH值与交换性酸、非交换性酸呈极显著负相关关系，与盐基饱和度、特别是Ca2+饱和度呈极显著正相关关系，与全盐含量和硝态氮含量呈极显著负相关关系。总之，灌溉方式能够影响设施土壤酸化特征，不同灌溉处理不同深度土层土壤酸化程度不同。从防治土壤酸化角度综合评价，滴灌抑制土壤酸化效果最好。