5. Conclusion(s)
The results (Refer to section 4) show that dual polarized SAR data along with optical multispectral data if used in a synergetic way by taking the advantages of both in terms of parameters that can be derived from them can be used in a simple modelling approach for Root Zone soil salinity estimation. Till now, most soil salinity studies were concentrated only upon the surface soil salinity despite using highly advanced datasets which were costly and sophisticated laboratory tests of soil samples. This study not only conducted in a highly cost-effective manner but also aimed at a simple, robust, and accurate approach. The results show that the study has been highly accurate with high values of R2-statistics of 0.997 and 0.958 in training and testing stages, respectively. The accuracy and goodness of model fit was further strengthened by the F-test and DW tests as mentioned in results section. The novelties from this study are that this study is innovative in a manner that it uses Microwave and Optical data from satellites, thermal data from thermal imaging sensor from field thus giving it a multi sensor approach for soil salinity estimation at sub-surface level with high accuracy with a simple approach. The study made use of freely available Sentinel-1 SAR and Sentinel-2 optical satellite data, and no sophisticated laboratory analysis hence making it cost-effective and time saving. The study estimates root zone soil salinity from satellite data unlike most other studies which were confined to surface soil salinity estimation using remote sensing.
The study establishes a fact that remote sensing could be used effectively and accurately for root zone soil salinity estimation which is a major cause of crop failure and low yields world-wide. The findings could be used for planning and taking timely measures for soil health enhancement.
As an improvement and future extension to the work, a longer time series SAR dataset could be utilised at higher wavelengths (L and S band) at monthly intervals and soil salinity variations can be studied with crop growth monitoring simultaneously. At present, the study has been conducted for Rupnagar district of Punjab. Further the technique is being implemented for other areas in India and is expected to deliver similar results.