Microwave Sensing Data Applicationin Soil Salinity Monitoring

Soil salinity caused by natural or human-induced processes is a major environmental hazard. The global extent of primary salt-affectedsoils is about 955 M ha, while secondary salinization affects some 77 M ha, with 58% of these in irrigated areas. Nearly 20% of all irrigatedland is salt-affected, and this proportion tends to increase in spite of considerable efforts dedicated to land reclamation. This requires careful monitoring of the soil salinity status and variation to curb degradation trends, and secure sustainable land use and management. It is very important to study the quality, the scope, the area, the geographic distribution, the dynamic change and the degree of saline soils. Multitemporal optical and microwave remote sensing can significantly contribute to detecting temporal changes of salt-related surface features. opitical remote sensing, combined with ground data, have shown potential formapping depth of salinity occurrence.This article uses the radar images as the most important data, which is also the application of radar images for the first time in arid area of Xinjiang.1) The research of SAR data preprocessing includes geometrical correction , speckle reduction and image inhancement. The quality of preprocessing is important for the application's reliability and accuracy.The result indicated that the inhance Lee filter methode is most useful of image filterring for the detatcing soil salinity . It is preserving the radiometry and spatial resolution of the individual channels;The DEM is not necessary in the geometrical correction of flat area;The best band combination is L-HV band for red , L-HV band for green and C-HV band for blue,which is most effective for image enhancing on soil salinity detection.2) Analysese of radar backscattering properties of the saline soil' surface and typical ground objects in reaserch area. It is shown that the oder of the backscattering coefficient of tipical objects is residential>famland >gravel> saline soil> clay stone>water,also the backscattering coefficient of tipical objects in L band is larger than the C band and it is appeared declining trend; The higher the extent of soil salinity and the band'length is ,The smaller the saline soil's backscattering coefficient is presented;The standard deviation of the different extent saline soil'backscattering coefficient in the L band is smaller than in the C band,it is testified that L band SAR data most efficient for the detection on the soil salinity compared with C band SAR data;3) Analyses of radar polarization signal of the saline soil'surface, the result shown that the backscattering coefficient of saline soil'surface in the same polarization radar signal is larger than the cross polarization radar signal ; the both of them are proved most usful information for the detection on the soil salinity,among them the HH is more efficient for detenction on the serious saline soil and high enxten saline soil, the HV is more efficient for detenction on the light extent saline soil.4) It is shown that the backscattering characteristics of sline soil change sharply with the temporal, while the backscatter characteristics of the water,the residential area, gravel, clay stone is small change;5) Research of S1R-C SAR data application in soli solnity monitering. A ase on multi-temporal SAR im ages using in solnizaion land classfication was presented. PC1 and dual polarization information is good for saline soil classification; The experimental result show that the spring SAR image most effect to detect soil solinizaion compared with the autumn SAR image, the temporal selection is most important in salnizaion land identification.In brief, the paper uses different research technique, and discusses the application of the radar image on the extraction of saline soil information in the arid area. This research applies the radar image to the extraction of saline soil information for the first time in Xinjiang, and comprehensively uses the superiority of other remote sensing and the spatial data to evaluate the saline soils quantitativel. its method and the conclusion has a higher theory and practice value to the examination of saline soils information in the arid area of Xinjiang.