Water is an important resource in agriculture. Crops require water to survive and grow. Water acts as the medium of transportation for conveying soil nutrients to all parts of a plant. Soil moisture is the quantity of water contained in the soil at a particular point in time. It controls water and heat energy exchanges between the land surface and atmosphere through evaporation and transpiration. Monitoring soil moisture on agricultural fields is, thus, a crucial component of crop performance monitoring and implementation of appropriate interventions (Gherboudj et al., 2011; Muller and Décamps, 2001). For example, soil moisture information can assist in scheduling irrigation. It has also been found useful in crop yield estimation.
Analysis of RS images, coupled with ground-based soil moisture estimates, can provide information on the spatial distribution of soil moisture (Muller and Décamps, 2001). This is often based on establishing a relationship between soil surface reflectance (from the RS image) and ground-based estimations. An optimal relationship can be established when both measurements are made simultaneously. In recent years, the use of Synthetic Aperture Radar images for determining the spatial distribution of soil moisture has become popular (Gherboudj et al., 2011; Susan Moran, 2000).