A Weighing Lysimeter for Evapotranspiration and Root Measurements1
- William A. Dugas,
- Dan R. Upchurch and
- Joe T. Ritchie2
Crop water use is intimately tied to soil water and rooting patterns. Therefore, a lysimeter was fabricated which is unique in that root density and water content measurements can be made throughout an undisturbed soil profile coincident with whole-profile evapotranspiration measurements. With this lysimeter, interrelationships throughout this soil profile between rooting depth and density, soil water content, plant water uptake, and evaporative demand can be evaluated. The lysimeter was constructed with a steel outer and inner box. The inner box contained an undisturbed soil monolith and was set on a scale, which in turn was set on the outer box floor. The 2.0 by 1.5 by 2.54 m monolith was obtained by forcing a steel box over a soil pedestal. Root growth and density and soil water are capable of being monitored throughout the monolith by using 36 clear, extruded acrylic tubes that were inserted horizontally through the monolith at various depths. Most of the soil mass is counterbalanced and the system is capable of resolving water mass changes equivalent to 0.02 mm. Evapotranspiration rates determined from the lysimeter compare favorably with empirical estimates. Costs for the facility and manpower requirements for operations and maintenance are substantial. However, root and soil water measurements, which are possible with this lysimeter, in conjunction with total-profile water loss measurements, provide a means for quantitatively evaluating interrelationships throughout the profile between these important phenomena.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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