Design, fabrication, and operation of an in-situ microlysimeter for estimating soil water evaporation

Authors: Marek, Gary; Colaizzi, Paul; Evett, Steven - Steve; Moorhead, Jerry; Brauer, David; Ruthardt, Brice

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2019
Publication Date: 6/12/2019
Citation: Marek, G.W., Colaizzi, P.D., Evett, S.R., Moorhead, J.E., Brauer, D.K., Ruthardt, B.B. 2019. Design, fabrication, and operation of an in-situ microlysimeter for estimating soil water evaporation. Applied Engineering in Agriculture. 35(3): 301-309. https://doi.org/10.13031/aea.13140.
DOI: https://doi.org/10.13031/aea.13140

Interpretive Summary: Evapotranspiration (ET), or crop water use is the major consumptive use of irrigation and precipitation. Water scarcity has led to agricultural research that aims to maintain crop yields while reducing ET. Partitioning of ET into evaporation (E) and transpiration (T) is needed for further understanding of water interactions within the soil-plant-atmosphere continuum. However, partitioning ET is difficult and requires direct measurements of E or T. Well-designed and fabricated microlysimeters can be used to measure E from agricultural soils. Scientists at USDA-ARS at Bushland present design, fabrication, installation, and operation details of an inexpensive, in-situ microlysimeter for estimation of E. Example data and analysis is also provided.

Technical Abstract: Evapotranspiration (ET) or crop water use is the major consumptive use of irrigation and precipitation, commonly accounting for the largest component of the water balance. As water resources become scarce, agricultural research aims to increase water use efficiency by maintaining profitable crop yields while reducing ET. Advanced understanding of ET in the soil-plant-atmosphere continuum requires quantification of evaporation (E) and transpiration (T) components. However, the partitioning of E and T can be challenging even when using high quality ET data. Microlysimeters can be used to measure E from the soil surface and estimate T by subtraction using quality ET data. However, an understanding of the limitations of small, hydraulically isolated microlysimeters is required for meaningful interpretation of results. Proper design, fabrication, and operation of microlysimeters can yield good estimates of E from bare soil. Multiple microlysimeters and strategic placement may be required for accurate estimates of E in row crops, particularly during incomplete plant canopy conditions. Periodic weighing of lysimeter cores allows for time-averaged measurements of E but precludes E rate data at finer time scales. Design and testing of continuous weighing platforms to improve temporal density of microlysimeter measurements is needed. We present design and fabrication details of a compact, inexpensive, in-situ microlysimeter for field estimates of E in agricultural soils. Installation and operation techniques are also provided with discussion of example field data.