Microwave Backscatter Dependence on Surface Roughness, Soil Moisture, And Soil Texture: Part III-Soil Tension

Results are presented of an experimental program to determine the impact of soil texture on radar response to soil moisture present within nonvegetated soil surfaces. These findings extend previous reports which document the experimental relationship between the radar backscattering coefficient σ° and soil moisture for bare soil [1] and soil under crop canopies [2]. In confirmation of previous results [1] and [2], the sensitivity of σ° to surface gravimetric or volumetric soil moisture is shown to be inversely related to clay content of the soil. As a result, gravimetric or volumetric moisture indicators exhibit poor performance in moisture estimation algorithms for complex multitextured soils. However, estimation algorithms incorporating some knowledge of soil water retention as a function of soil matric potential, or tension, display strong correlation with radar response, typically r ≈ 0.8, and are shown to be relatively independent of soil texture. These findings are shown to be consistent with soil dielectric properties [3]-[5].