ARS | Publication request: EVALUATION OF A TIME DOMAIN REFLECTOMETRY SLED FOR MAPPING SOIL WATER CONTENT

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: October 15, 2005
Publication Date: November 7, 2005
Citation: Starr, G.C., Sorensen, R.B., Rowland, D., Sullivan, D.G. 2005. Evaluation of a time domain reflectometry sled for mapping soil water content. American Society of Agronomy Meetings. CD-ROM

Technical Abstract: A rapid method for mapping soil water content would be valuable for agricultural and scientific applications such as precision irrigation. A sled type measurement device with a time domain reflectometer and global positioning system was evaluated for measuring soil water content following tillage. The system was tested in the laboratory using three soils of varying texture and at a field site where non-uniform irrigation was used to induce spatial variability. The system exhibited a linear response (coefficient of determination, R2 = 0.70-0.93, root mean square error, RMSE = 0.022-0.034 m3m-3) to variation in volumetric soil water content for all soils tested. A single calibration fit all three soils with slightly higher error (R2 = 0.74, RMSE = 0.042 m3m-3) than the individual calibrations. Field trials showed that the system could detect soil water variability induced by non-uniform irrigation. The substantial nugget semi-variance (30-42 % of sill) was comparable to conventional TDR. The speed (2 second repetition rate) and ease of the sled method should allow mapping larger areas at greater resolution. This system can provide a valuable tool for many scientific, landscape, and agricultural applications.