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United States Department of Agriculture

Agricultural Research Service

Title: Field Evaluation of a Time Domain Reflectometry Sled for Mapping Soil Water Patterns

Authors
item Starr, Gordon
item SORENSEN, RONALD
item Rowland, Diane
item Sullivan, Dana

Submitted to: Agronomy Abstracts
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. Field evaluation of a time domain reflectometry sled for mapping soil water patterns. Agronomy Abstracts. CD-ROM

Technical Abstract: To address the need for rapid, high-resolution mapping of field-scale soil water distributions, a time domain reflectometry (TDR) sled was developed and tested on two Greenville soils (kaolinitic, thermic Rhodic Kandiudults; 1-5% slope) in southwest GA. A surface probe was constructed by fitting three steel rods into machined slots in a 2.5 cm slab of Delrin plastic. After the probe was mounted on a steel frame and pulled across the soil surface plowing and cultivating to a depth of 20-25 cm. Proximate stationary and moving sled data were compared to conventional TDR probes that integrated depths of 0-2.5 cm, 0-20 cm, and 0-30 cm at 33 locations in the field. The moving sled was used to obtain volumetric water content data at approximately 6 m intervals along parallel transects separated by 30 m. These volumetric water content data were mapped using ordinary kriging and compared with 0.5 m elevation contours. The moving vs. stationary sled were in agreement and correlated linearly (R2 = 0.27). Correlations between sled and conventional TDR measurements decreased with integration depth. The semi-variogram fit an exponential model with a range length of 119 m. Soil water was concentrated along low lying areas and drainage pathways. This system is capable of collecting soil water and global position data every four seconds. These results suggest that the TDR sled shows promise as a tool to provide high-resolution estimates of soil water content variability at field scales.

Last Modified: 7/28/2014
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