Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: January 12, 2008
Publication Date: May 18, 2008
Citation: Jabro, J.D., Evans, R.G., Kim, Y., Iversen, W.M. 2008. In-situ field capacity and soil water retention measurements in two contrasting soil textures. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). June 29 - July 2, 2008. Providence, Rhode Island. Technical Abstract: Knowledge of the in-situ field capacity and soil-water retention curve for soils is important for effective irrigation management and scheduling. The primary objective of this study was to estimate in-situ field capacity and soil water retention curves in the field using continually monitoring soil moisture sensors in two contrasting-textured soils. The two soils are Lihen sandy loam and Savage clay loam. Six metal square frames of 117 cm * 117 cm and 30 cm in height were inserted 5- to 10 cm into soil to prevent lateral water movement. The frames were spaced at approximately 40-m intervals on a 200 m transect to account for soil variability across the field. Two Time Domain Reflectrometry (TDR) sensors were installed in the center of the frame and two Watermark (WM) sensors were installed in the SE corner at 15 and 30 cm depths to continuously monitor soil water content and water potential, respectively. A neutron probe access tube was installed in the NE corner of each frame to measure soil water content used for TDR calibration. Neutron probe readings were taken every 6 hours in sandy loam and daily in clay loam soil. The soil inside each frame was saturated by applying approximately 18 cm of water intermittently to saturate the soil to a 40- to 50 cm depth. Frames were then covered with plastic tarps to avoid any evaporation from the soil for approximately 50 hr on sandy loam and 7 days on clay loam soil. Nine soil cores were taken at the 0- to 10 cm, 10- to 20 cm and 20- to 30 cm depths from each framed soil area for determination of gravimetric water content and bulk density. In-situ field capacity values were estimated in terms of water potential and moisture content from WM and TDR sensor data as well as from the gravimetric method. Several exponential equations were developed between soil water potential and water content.