强异质层状土壤条件下农田GSPAC水盐运移机理与模型

Soil in cropland uaually has distinctly stratified structure, which provides opportunity for fingering flow, especially in the high permeability soil layer. This makes water and salt transport processes in Groundwater - Soil - Plant - Atmosphere continuum (GSPAC) more complicated. Through laborotary and field experiments, data collection of long term field monitoring, as well as theoretical analysis and model simulation, processes and patterns of water and salt transport in GSPAC will be studied at cropland with shallow groundwater table that is prone to salinization. First, finger formulation and evolution characters in distinctly stratified soil, and their responses to the changing boundary condition will be analyzed, and simultaneous water and salt transport model (FWSM) in distinctly stratified soil considering fingering flow will be developed. Second, water and salt transport behavior in cropland under different irrigation scheduling will be analyzed, including water and salt dynamics in the crop root zone, fingering flow evolution in the ground layer, and the exchange of water and salt with groundwater. As a result, coupled water and salt transport model in GSPAC with distinctly stratified soil structure will be developed. And finannly, through long term data analysis and scenario simulations, reasonable irrigation and drainage scheme will be explored for cropland salinization control and high efficient use of irrigation water. The study can enrich the theory of fingering flow and solute transport in stratified soil and the theory of water and salt transport in GSPAC. It will also benefit the agricultural water saving and protection of agricultural water and soil environment.

农田土壤普遍存在强异质层状结构，特别是其中的强透水性底土层易诱发指流，使地下水-土壤-植物-大气连续体（GSPAC）水盐运移规律更为复杂。拟选取地下水浅埋区易盐渍化农田为研究对象，通过室内外试验和长期定位监测资料的搜集，结合理论分析和模型模拟，开展以下研究工作：⑴ 分析强异质层状土壤中指流形成、发育特征和溶质分布、穿透规律及其对变化边界的响应，建立强异质层状土考虑指流形成发育和动态边界响应的水盐耦合运移模型（FWSM）；⑵ 分析具有强异质层状土的农田GSPAC水盐运移规律，包括根区水盐动态响应、强透水性底土层中的指流发育及其与地下水的水盐交换特征，结合FWSM建立强异质层状土条件下的GSPAC水盐耦合运移模型；⑶ 通过资料分析和情景模拟，初步提出农田盐碱化防控和灌溉水高效利用的合理灌排方案。研究成果可丰富层状土指流和溶质运移理论以及GSPAC水盐运移理论，并促进农业节水和水土环境保护。

农田土壤普遍存在层状结构，特别是其中的强透水性底土层易诱发指流，使地下水-土壤-植物-大气连续体（GSPAC）水盐运移规律更为复杂。本项目通过室内土柱试验和室外田间试验的试验监测，结合理论分析和模型模拟，研究了层状土中的水盐运移动态及作物生长状况，获得了一系列研究成果：上细下粗型层状土能够减小入渗中的稳定入渗率，同时对土壤蒸发具有抑制作用；当下层土壤较粗时，会诱发指流，指流的发生和发展具有随机性，两区模型比传统模型能更好的模拟上细下粗层状土中水盐运移的情况，模拟结果更为可靠；利用非饱和带水分运动方程、对流弥散方程和作物生长原理，构建了水分运动、溶质运移和作物生长的耦合模型（LAWSTAC），模型中考虑了土壤层状结构对水分和溶质的动态影响；运用耦合模型对田间夹砂土进行了模拟分析，发现夹砂土埋深60 cm、厚度20-30 cm更适合土壤盐渍化和地下水埋深较浅地区的农业生产。此研究成果可丰富层状土指流和溶质运移理论以及GSPAC 水盐运移理论，并促进农业节水和水土环境保护。