3.1 Band Rationing for NDSI
From the clipped image of Rupnagar, the salinity sensitive bands were
used for generation of NDSI. The NDSI values range from -1 to1 with 1
representing high salinity values in soil(Konukcu et al., 2006). Studies
reveal that the Red and NIR bands are the most sensitive to the soil
ions causing salinity(Rengasamy et al., 2003). The following formula was
used for the purpose-
NDSI=\(\frac{(Green-SWIR)}{(Green+SWIR)}\) (1)
Since the bands 3 (GREEN) and Band 11 (Short Wave InfraRed-SWIR) have
spatial resolutions of 10 m and 20 m respectively, the optical image
bands were resampled at 14 m spatial resolution (same as that of
multilooked Sentinel-1 SAR image). Based on this, surface Salinity maps
for entire Rupnagar district were generated for the study dates of
4th December and 27th December 2019
and 20th January 2020. The application of fertilizers
mainly DDT (Dichlorodiphenyltrichloroethane) affected the salinity
levels, declining between the first two dates of early stage of wheat
crop growth to slightly rising in January. The details are shown in the
maps in Figure 3-