Monitoring and evaluation of soil salinity in terms of spectral response using geoinformatics in Cuddalore environs

Soil degradation is a global problem that severely hampers the production of food needed to sustain the growing population. This study is aimed at monitoring, mapping and assessing the soil degradation in the Cuddalore district. Mapping of soil degradation is instrumental in understanding the spatial extent and rate of degradation. Key soil properties, such as pH, salt content, EC and ESP determine the salinity status of soils and this reflects in the spectra of surface samples interacting with organic matter, clay content, etc. Change detection can be assessed by post-classification comparison aiming to uncover the differences between the images of three different periods. The salinity variations in the study area was done using Landsat TM and ETM+ images and the changes were quantified for the years 1977, 2000 and 2009. A computerised soil degradation severity assessment was adopted using geomatic tools to process, manage and analyse the raster and thematic datasets. The indices used in this research are: The Normalized Differential Vegetation Index “NDVI”, Salinity Index, Normalised Difference Salinity Index. SAVI was found to be effective in discriminating plants under severe and moderate conditions of soil salinity and in non-saline conditions. Temporal trend analysis technique was done to detect significant changes in the soil verses vegetation conditions. The results showed a clear deterioration in vegetative cover, an increase of salinity accumulations and a decrease in soil/vegetation wetness of the total study area. Salinity had increased in the study area, with salinity increasing at a drastic rate during the past 30 years.