An Automated Microlysimeter for Long-Term Monitoring of Soil Evaporation.

The process of soil evaporation is of significance for a wide range of disciplines interested in monitoring and management of soil hydrologic regime. Applications are found in agricultural, environmental, meteorological, commercial, ecological and industrial sectors spanning from point-scale to watershed-scales and beyond. Soil evaporation has been thoroughly studied during the past century with many methods and models. However, none of the methods have adequately addressed the need for spatially distributed-, long-term-, in situ- and real-time-monitoring of soil evaporation. We present an automated design based on the microlysimeter concept with enhancements of a 60 cm deep lysimeter which is mounted on a 10 kg load cell for real-time output of water loss. The sample extraction and lysimeter installation are facilitated by a 75 mm diameter coring tool with an internal acetate sleeve to hold the soil sample. An external PVC sleeve is installed into the hole left by sample extraction, which then houses the load cell attached to the bottom of the 60 cm sample. The extended depth expands the useful operational life of the lysimeter beyond, approximately, 10 day limit found in 30 cm lysimeters in a previous study. Laboratory and field results demonstrate the utility of the enhanced microlysimeter design in long-term monitoring of soil evaporation.