Innovative Soil Fluoride Estimation Method: Dual Polarimetric Saline-Associated Fluoride for Agricultural Patches

Abstract Fluoride and its constituents in soil affect plant growth and public health. In this study soil fluoride was measured for the semi-arid regions in southern India, using Sentinel-1 data in conjunction with the Dual Polarimetric Saline Associated Fluoride model (also known as Fluoride model). A loss angle was estimated from laboratory-based dielectric components of soil samples with strong electrical conductivity under high and low fluoride conditions. The conductivity loss angle, real and imaginary dielectric constants were used to study fluoride salt's dielectric behaviour. The imaginary dielectric component sensitive to dielectric loss could predict fluoride across large areas over time. This was statistically analysed with R2 = 0.86, RMSE = 1.90, and Bias = 0.35 showing a promising depiction that C-band SAR data can distinguish fluoride levels over varied clay soil and soil with varying vegetation development. Moreover, the association between biomass and simulated fluoride helped to identify fluoride-tolerant and non-tolerant crops. The study found that Sorghum and Oryza sativa tolerate saline-associated fluoride, whereas Peanut and Allium do not. Furthermore, the model successfully retrieves fluoride from saline salts based on tangent loss.