A volumetric lysimeter system (VLS): an alternative to weighing lysimeters for plant-water relations studies

A closed, recirculating volumetric lysimeter system (VLS) consisting of 24 experimental plant growth units was constructed. The VLS measured irrigation and drainage volumes with pressure transducer trace analysis of irrigation reservoir/sump water elevation. To estimate crop evapotranspiration (ET), changes in soil moisture storage in the plant growth boxes were obtained with neutron probe measurements and were combined with the transducer data to estimate the complete water balance measurement of crop ET. Automated tensiometers, temperature sensors, and four-electrode salinity sensors were installed to monitor soil matric potential, temperature, and electrical conductivity of drainage waters, respectively, 10 times per hour. Plant response to evaporative demand was characterized with a high degree of resolution with the VLS transducer estimated ET detection of approximately 0.1 rum. The VLS provided rapid, reliable, and field-transferable research information. This provided us with the statistical power to compare variables of interest to study the interaction of water quality and quantity on plant ET. Data obtained from the VLS during the cultivation of two crops, alfalfa and tall wheatgrass, under various salinity and water stress treatments were analyzed with a response surface regression model. The model was able to attribute at least 89% of the variation in ET for each crop to salinity and applied water treatments. (C) 2003 Elsevier B.V. All rights reserved.