|Grattan, Stephen - UC DAVIS EXT, CA|
|Lieth, J - UC DAVIS, CA|
Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2003
Publication Date: January 20, 2004
Citation: POSS, J.A., RUSSELL, W.B., SHOUSE, P.J., AUSTIN, R.S., GRATTAN, S.R., GRIEVE, C.M., LIETH, J.H., ZENG, L. 2004. A VOLUMETRIC LYSIMETER SYSTEM (VLS): AN ALTERNATIVE TO WEIGHING LYSIMETERS FOR PLANT-WATER RELATIONS STUDIES. COMPUTERS AND ELECTRONICS IN AGRICULTURE. 43:55-68. Interpretive Summary: Agricultural irrigation efficiency is maximized when water applications to meet the demands of the crop are met while minimizing drainage below the rootzone. Some leaching of salts below the rootzone is essential to manage soil salinity within tolerable limits for yield maintenance, however, excess drainage creates unnecessary leaching that does not improve soil quality yet still contains salts that are transported below the rootzone. The optimization of these two conflicting processes is facilitated by the development of a volumetric lysimeter system (VLS). The system has the ability to automatically measure applied water, drainage water, and irrigation water salinity. By developing a range of water application rates and soil salinity profiles in the VLS, data are generated that can be analyzed to find the optimum combination of irrigation volumes and salinity concentrations that will maximize yield yet minimize drainage required to mitigate toxic soil salinity buildup. Efficient use of precious water resources while minimizing the threat of pollution to surface and ground waters by agricultural drainage is a very difficult and important challenge to irrigated agriculture thoughout the world.
Technical Abstract: A closed recirculating volumetric lysimeter system (VLS) consisting of 24 experimental plant growth units was constructed to measure irrigation and drainage volumes based on pressure transducer trace analysis of irrigation reservoir/sump water elevation. Changes in soil moisture storage in plant growth boxes were obtained with neutron probe measurements and are combined with the transducer data to estimate crop evapotranspiration. Automated tensiometers, thermistors, and four-electrode salinity sensors were installed to monitor soil matric potential, temperature, and electrical conductivity of drainage waters, respectively, ten times per hour. Plant response to evaporative demand is characterized with a high degree of resolution with the use of the VLS. The VLS provides rapid, reliable, and field transferable research information. The ability to maintain statistical power to compare variables of interest to the results of agricultural researchers studying the interaction of water quality and quantity on growth of agronomically important plant species and the resulting drainage patterns below the rootzone is less variable than would probably be available in all but the most elaborate field study. As an initial test, 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 surface regression techniques. The surface model was able to explain at least 98 percent of the variation in dry weight and drainage volume variables obtained from the VLS. The VLS provides an accurate alternative to weighing lysimeters