砂姜黑土孔隙的全谱识别与调控机理

Structure improvement of vertisol soil is one of the main problems in the middle-lower yield farmer land improvement in Huang-Huai-Hai Plain, the quantitative expression of soil pore in vertisol soil is an effective method to reveal the development process of unhealthy structure. In this proposed project, pore characteristics with different scales from mm to microns, and to nano in four typical vertisol soils will be investigated to reveal the control factors and reduction mechanisms. The main study content include: The characteristics of the number and morphology of pore structure of typical vertisol soils are analysed by a series of modern techniques such aslaser scanner, nitrogen adsorption and mercury porosimetry and synchrotron radiation micro CT, and identification theory method of the complete characterization of pore size distribution of vertisol soil will be developed. A water alternative control experiment and long-term field experiment will be conducted to reveal the effects of natural factors (soil texture, soil moisture, soil aggregate and soil organic matter) and the human factors (tillage and fertilization methods) on the formation of vertisol soil pore structure. Effect of the soil moisture and exogenous organic matter (straws) on the complete characterization of pore size distribution in vertisol soil were studied by the field experiments. Such efforts not only contribute to the development of the new theory of the complete characterization of pore size distribution in vertisol soil, but also provide theoretical basis and technical support for the middle-lower yield farmer land improvement in Huang-Huai-Hai Plain.

砂姜黑土结构改良是黄淮海平原中低产田改造的难题之一，定量表征土壤孔隙变化特征是揭示其不良结构产生机理的有效途径。项目以黄淮海平原砂姜黑土4类典型土种为研究对象，针对砂姜黑土毫米-微米-纳米尺度孔隙的全谱识别理论与方法展开研究。具体内容为：融合同步辐射显微CT-压汞仪-氮气吸附等检测技术，查明砂姜黑土全谱孔隙结构的数量及形态变化特征，创建砂姜黑土孔隙全谱识别方法；利用长期田间定位试验，静态解析关键控制因子（土壤质地、水分、团聚体和有机质）影响砂姜黑土全谱孔隙的内在机理；通过不同时间尺度的田间定位试验，动态验证土壤水分、外源秸秆碳对砂姜黑土全谱孔隙结构重建的调控效应。旨在尝试建立砂姜黑土孔隙的全谱识别理论及方法，拓展传统土壤物理学乃至非均质情形研究的新内涵，为黄淮海平原中低产田改造奠定理论基础。

砂姜黑土是黄淮海平原面积最大的中低产土壤之一（总面积约267万公顷，占全国砂姜黑土总面积的2/3），由于变性土的典型特征，解译其不良结构产生机理一直是相关研究难点。针对砂姜黑土区高度集约化种植模式下全谱孔隙（毫米-微米-纳米多尺度）检测方法缺失、关键影响因子机理不明的科学问题。本研究选取黄淮区砂姜黑土典型土种为研究对象，通过野外盆栽和田间定位等试验，运用土壤物理化学、土力学、生物学、计算机图形学以及数字图像学等学科最新技术手段取得了以下5个方面的创新成果。(1)形成了同步辐射显微CT（SR-μCT）-压汞仪（MIP）-氮气吸附（NAI）联合表征砂姜黑土全谱孔隙的理论方法体系。明确了不良结构产生机制主要是干湿交替下条件下，小于5μm的无效孔隙（包括超微孔隙和隐孔隙）膨胀和收缩的结果。(2) 初步探明了土壤粘粒、土壤有机质、土壤含水量及土壤团聚体是砂姜黑土大、中孔隙的关键控制因子，明确了外源有机碳通过自身碳输入增大土壤孔隙表面积、物理缠绕土壤粘粒形成大团聚体及增加砂姜黑土大、中孔隙的结构改良机制。(3)创建了砂姜黑土大孔隙三维结构信息提取的方法体系。提出了分形维数作为砂姜黑土改良效果的评价新指标，研发了土壤三维结构无损取样的设备装置。(4)创新发现了生物质碳、有机肥对砂姜黑土小孔隙及微孔隙的协同效应及调控机制。(5) 创新构建了砂姜黑土黑色物质、纳米级有机-矿物复合体及生物标志物的物理提取方法。该研究为《国家耕地质量保护与提升行动》、《中国耕地质量等级调查与评定》以及黄淮海平原中低产田改造提供了科学依据与技术支撑。