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Title: DETERMINATION OF SOIL WATER PHYSICAL PROPERTIES UNDER FIELD CONDITIONS USING CAPACITANCE PROBES AND GUELPH PERMEAMETER

Author
item FARES, A - UINV. OF FLA. LAKE ALFRED
item Alva, Ashok
item NKEDI-KIZZA, P - UNIV. OF FLA. GAINESVILLE
item ELRASHIDI, M - UNIV. OF FLA. GAINESVILLE

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2000
Publication Date: 10/1/2000
Citation: FARES, A., ALVA, A.K., NKEDI-KIZZA, P., ELRASHIDI, M.A. DETERMINATION OF SOIL WATER PHYSICAL PROPERTIES UNDER FIELD CONDITIONS USING CAPACITANCE PROBES AND GUELPH PERMEAMETER. SOIL SCIENCE, 165:768-777. 2000.

Interpretive Summary:

Technical Abstract: Soil hydraulic conductivity (K)-water content (0)-pressure head (h) relationships (K-O-h) are key parameters for modeling water flow and chemical transport through the soil. The objective of this study was to use the Instantaneous Profile method in combination with capacitance probe, tensiometer, the Guelph permeameter, and van Genucheten hydraulic functions sto determine the hydraulic conductivity-water content-pressure head relationships of a Candler fine sandy (hyperthermic, uncoated, Typic Quartzipsamments) soil. The soil was flooded for more than 2 h to achieve a constant water content through the profile and was then covered with a plastic sheet to prevent evaporative loss or addition of rain water. The capacitance probe and tensiometer readings were taken simultaneously at 0.1-, 0.2-, 0.4-, 0.7- and 1.1-m depths. Water content and hydraulic conductivity values decreased substantially as water redistributed through the soil profile after saturation. Saturated hydraulic conductivity, measured with the Guelph permeameter for the five soil depths, varied between 6.1 and 10.0 m/day. More that 50 percent of the soil water was drained from the soil profile within 8 to 10 h following saturation. The analytical RETC (RETension Curve) model was used to extend soil water release curves beyond the limited range of tensiometer suction measurements. This study demonstrated that the capacitance probe is a practical tool that can be used in combination with the Guelph permeameter and analytical fitting software (RETC) to determine in-situ soil water characteristic curves, saturated hydraulic conductivity, and k(0) at different soil depths.