Passive Microwave Study of Salt Affected Agricultural Soil
Salt affected agricultural soil from superficial horizon of local profile of Alwar region with textural composition sand=30.2%, silt=59.7% and clay=10.1% has been selected for an estimation of observable parameter of passive microwave remote sensing. Artificially salinized and moistened soil samples with different concentrations in part per million (ppm) of Sodium Chloride corresponding to 0 ppm to 35000 ppm soluble in conductivity water are prepared.The real and imaginary parts of dielectric constant ε’ and ε” for artificially moistened and salinized soil with Sodium Chloride are determined at different levels of salinization. Real and imaginary part of dielectric constant is measured by wave-guide cell method at a single microwave frequency 9.78 GHz and at constant temperature 330C. The Fresnel reflectivity of salinized and moistened soil is determined for different observation angles. Further, Microwave emissivity of salinized soil is also calculated with suitable model calculations in view of passive microwave remote sensing. Microwave emissivity decreases with both salinity and moistness. Effect of salinity on emissivity is very small and considerable only at higher wetness of soil. In dry soils no impact of salinity observed on emission behaviour. High dielectric contrast between emitting layer of soil and air causes more energy to reflect back within the soil media than that of transmitted out in air. Hence, emissivity of soil decreases as salinity increases.
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