New results in integrating passive and active remote sensing methods to assess soil salinity: A case study from Jezre'el valley, Israel

Irrigated lands in Israel are subjected to salinization processes, mostly as a result of low-quality irrigation water. The Jezre'el Valley in northern Israel, which exemplifies this phenomenon, was selected for this study. This area has been characterized by increasing soil salinity over the years, with consequent increase in soil sodium adsorption ratio, leading to significant deterioration of the soil structure and a reduced infiltration rate. The traditional methods of soil mapping (soil sampling, laboratory tests, and mapping) are time-consuming and do not provide near-real-time information. We evaluated an alternative method consisting of passive and active remote sensing: (i) in situ and airborne sensor spectral measurements, (ii) frequency domain electromagnetic, and (iii) ground penetration radar. A partial least-squares regression model was used to assess a thematic electrical conductivity map of the surface based on the airborne hyperspectral images. A sub-surface salinity map was also generated by applying the surface-to-sub-surface correlation on the surface thematic electrical conductivity map. The generated maps were found to be in good agreement with those based on laboratory chemical data. The results indicated that traditional methods are correlated with remote sensing from the air and ground observations, which can therefore account for soil salinity. Importantly, merging the passive and active remote sensing methods yields a better understanding of the underlying processes than either approach alone.