Figure 5. Correlation between surface EC and sub-surface (60 cm depth) soil EC for 4th December 2019, 27thDecember 2019, and 20th January 2020.
The surface parameters from field were found to directly correlate to the satellite data parameters of SAR backscatter and NDSI, hence an attempt was made to correlate the satellite data parameters with sub-surface field parameters which showed high correlation as shown in Figures 4 and 5 above. Hence, sub-surface soil moisture and EC values were used for regression analysis along with satellite data. 60 cm depth was chosen since in early stage of wheat crop growth, this is the root zone depth of wheat crop.