Lysimeter Design, Construction, and Instrumentation for Assessing Evaporation From a Large Undisturbed Soil Monolith

The design, fabrication, and evaluation of equipment used to remove a 1.5 metric ton (3300 lb) soil monolithand an associated laboratory lysimeter are described herein. A mechanism was developed to extract a relatively largemonolith with minimal disturbance of the soil and with a relatively simple apparatus. To avoid using a poweredmechanism to push a lysimeter into the soil a trencher, backhoe, incremental trimming of excess soil and a cylindricalknife were used in conjunction with hydraulic jacks to sever the base of the soil monolith. A thin wall metal cylinder,which served as the lysimeter shell, was then placed over the monolith and the void filled with polyurethane foam. Alaboratory lysimeter, using the principle of counter balancing, was designed to test evaporation of the extracted monolithfor a trickle irrigation experiment. The water holding tank was integrated into the lysimeter to increase accuracy. Theachieved weighing sensitivity of the lysimeter corresponds to an evaporation rate of 0.025 mm/h (0.001 in/h).