REMOTE SENSING FOR CROP AND WATER MANAGEMENT IN IRRIGATED AGRICULTURE
Location: Water Management and Conservation Research
Title: Field thermal infrared emissivity dependence on soil moisture
Submitted to: Remote Sensing in Hydrology Symposium
Publication Type: Proceedings
Publication Acceptance Date: September 20, 2010
Publication Date: September 27, 2010
Citation: Sanchez, J.M., French, A.N., Mira, M., Hunsaker, D.J., Thorp, K.R., Valor, E., Caselles, V. 2010. Field thermal infrared emissivity dependence on soil moisture. Remote Sensing in Hydrology Symposium. 10-11.
Interpretive Summary: Increasing demands for water resources in arid lands may cause shortages for farmers. To help manage these farmers will need tools to help them make decisions about when, where, and how much to irrigate. Remote sensing of land surface temperatures is one such tool, since temperatures are indicators of soil moisture content. However, distinguishing between adequate and inadequate amounts of water in the uppermost soil layers can be difficult. To help solve this problem, an experiment over an irrigated soil was conducted in 2010 at Maricopa, Arizona to measure the relationship between remotely sensed temperatures and soil moisture content after sequential irrigations. The measurements showed that thermal emissivity- a property that relates apparent temperatures to actual temperatures-is correlated in a complex way with soil cracking, and not just to soil moisture. This finding may help improve accuracy of remote sensing of land surface temperatures and as a result will also improve the accuracy of estimating soil water content at farm-scales. This research benefits agricultural research scientists, water managers, and future growers relying upon irrigation resources.
Emissivity dependence on soil water content has been already reported and modeled under controlled conditions at the laboratory. This study completes and extends that previous work by providing emissivity measurements under field conditions without elimination of impurities, local heterogeneities or soil cracks appearing in the drying process. A bare soil plot was selected in central Arizona, USA. The soil plot was flood irrigated every 2-3 days and left to dry. Field emissivity measurements were collected for different values of soil water content. An overall increase of emissivity with soil moisture was obtained. Also, it was shown that deterioration of the soil surface tends to reduce the emissivity spectral contrast. Relationships obtained by Mira et al. (2010) were tested and compared with the field measurements.