基于电磁感应仪的田间土壤盐渍度及其空间分布定量评估

 【目的】阐明黄河三角洲地区土壤盐渍化空间变异特征，探讨利用电磁感应仪定量评估田间土壤盐渍化的空间分布。【方法】运用电磁感应仪(EM38和EM31)及其移动测定系统，结合GIS和地统计学方法, 研究了该地区典型地块土壤盐分与磁感表观电导率间的响应关系，分析了表观电导率的空间变异特征，并对土壤盐分空间分布进行了定量评价。【结果】土壤表观电导率与盐分含量具有良好的相关性，采用EM38h＋EM31h的优化测定组合可以提高土壤盐分的解译精度；表观电导率EM38h、EM31h的空间变异结构都表现出复合的尺度效应，较好地符合球状套合模型；EM31h的空间自相关程度强于EM38h，短程变异是构成EM38h、EM31h空间异质性的最主要部分；结构性因素是主导土壤盐分空间分布格局的最直接因素，随机性因素是加快盐分分布格局形成的重要因素。由盐渍化分级可知：研究区总体属于重度盐化土类型，且呈现一定的盐分表聚趋势；各土层中几乎不存在非盐化土，盐土与重度盐化土是最主要的土壤类型。【结论】该研究结果为不同尺度(从农田到区域)土壤属性调查与质量评价提供参考依据，并为农业水土资源的高效利用提供指导。

Quantitative Evaluation of the Field Soil Salinity and Its Spatial Distribution Based on Electromagnetic Induction Instruments

Taking into account the problem of salinization existing in Lower Yellow River Delta, with the application of electromagnetic induction instruments (EM38 and EM31) and their mobile sensing system, response relation between apparent soil electrical conductivity and soil salinity in typical field of the Yellow River Delta was analyzed by using GIS and geostatistics, then the spatial variability of soil salinity characterized by apparent soil electrical conductivity was discussed and spatial distribution of soil salinity was further evaluated quantitatively. Results indicated that apparent soil electrical conductivity was well correlated with salinity, and interpretation accuracy of soil salinity at different layers could be improved when adopting the optimal combination of EM38h and EM31h. Apparent soil electrical conductivity EM38h and EM31h both exhibited moderate spatial variation, and nested spherical models were fitted for semivariance of EM38h and EM31h because of the compound scale effect of their spatial structures. Spatial autocorrelation of EM31h was better than that of EM38h, and short-range variation was the chief constitute of spatial heterogeneity for both EM38h and EM31h. Spatial distribution pattern of soil salinity was directly controlled by structural factors, while stochastic factors were of importance for the formation of spatial distribution patterns. Salinization classification showed that heavy salinized soil was the predominant soil type as a whole and soil salinity exhibited the trend of top enrichment in the study area. The predominant soil types were saline soil and heavy salinized soil while the distribution area of desalinized soil was negligible at all layers. The research results provided a reference for the survey and quality evaluation of soil properties at different scales ranging from farms to regional levels, and it could be used as the guide for the efficient utilization of agricultural water-soil resources.