Precision Lysimeters for Evapotranspiration and Field Water Balance Studies.

Recent technological improvements in monolithic weighable lysimeters have made them viable tools for research and monitoring tasks in hydrology, climatology, bioremediation, soil science and agronomy.  These lysimeters are installed without disturbance to the enclosed soil profile, and are instrumented to maintain internal water potential distributions similar to those in the surrounding, undisturbed soil.  A drop-ring around the top of the lysimeter allows tillage of the surface soil along with the soil surrounding the lysimeter to assure that the lysimeter response is representative of the surrounding field.  Precise measurements of lysimeter mass combined with drainage measurements at field matric potential allow tracking of water balance with a resolution of 0.01 mm. 
We have installed precision lysimeters with a surface area of 1 m² and depths of ­1 m and 2 m.  These have been used to monitor water balance of organic versus conventional farming with winter wheat, maize and pumpkin continuously over the past 5 years.  We show the method of installation, instrumentation within and around the lysimeter, and representative results from measurements of precipitation, evaporation, drainage, soil water potential, and leachate composition.