Systematic discrimination of irrigation and upheaval associated salinity using multitemporal SAR data

The increasing salinization in the soil profile by irrigation water and groundwater upheaval is a widespread issue and considered as a major threat to agricultural production in arid and semi-arid regions. The present study aimed to propose a systematic SAR simulation involving the imaginary part of dielectric constant measurements of two consecutive seasons (dry and wet) to quantify and discriminate the irrigation-induced and upheaval-associated salinity from total salinity levels and investigate its impact on crop growth. The Sentinel-1 data of C-band frequency (5.36 GHz) acquired for both the dry and wet spells from 2015 to 2019 was instrumental in the present study. The total soil EC (Electrical Conductivity) was quantified from the imaginary part of dielectric constant (ε″) using semi-empirical microwave simulation "DSDM-SS". Irrigation-induced salinity (ε_Irrigation″) and upheaval-associated salinity (ε_Upheaval″) were extracted from ε″ by proposing a site-, and climatic-specific novel model. The ε_Upheaval″ and ε_Irrigation″ have shown promising statistical significance with the in-situ soil EC (R² = 0.89, p = <0.001, rMSE = 1.08, Bias = 0.584) and groundwater EC measurements (R² = 0.85, p = <0.001, rMSE = 1.28, Bias = 1.16). The study found that the rate of salinity increase over time due to irrigation (77%) was considerably higher than the upheaval (42%) process. This demonstrated that the intensive use of groundwater for irrigation has a higher impact on vegetation vigor (θ = -0.87) than the upheaval process. The study revealed that crop failure in the dry season was provoked by osmotic stress and waterlogging conditions.