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 m etric ton (3300 Ib) soil monolith and an associated laboratory lysimeter ar e described herein. A mechanism was developed to extract a relatively large monolith with minimal disturbance of the soil and with a relatively simple apparatus. To avoid using a powered mechanism to push a lysimeter into the soil a trencher backhoe, incremental trimming of excess soil and a cylindr ical knife were used in conjunction with hydraulic jacks to sever the base of the soil monolith. A thin wall metal cylinder which served as the lysime ter shell, was then placed over the monolith and the void filled with polyu rethane foam. A laboratory lysimeter; using the principle of counter balanc ing, was designed to test evaporation of the extracted monolith for a trick le irrigation experiment. The water holding tank was integrated into the ly simeter to increase accuracy. The achieved weighing sensitivity of the lysi meter corresponds to an evaporation rate of 0.025 mm/h (0.001 in/h).