Facilitating soil-and plant-water research through the use of TDR

Topp, G. Clarke, Lapen, David R., Cook, Freeman J., Morrison, Malcolm J. and Pillai-McGarry, Usha (2006). Facilitating soil-and plant-water research through the use of TDR. In: TDR 2006 Technical committee, TDR 2006: 3rd International Symposium and workshop, Purdue University, West Lafayette, Indiana USA, (1-22). 17-20 September 2006.

Author Topp, G. Clarke
Lapen, David R.
Cook, Freeman J.
Morrison, Malcolm J.
Pillai-McGarry, Usha
Title of paper Facilitating soil-and plant-water research through the use of TDR
Conference name TDR 2006: 3rd International Symposium and workshop
Conference location Purdue University, West Lafayette, Indiana USA
Conference dates 17-20 September 2006
Place of Publication United States
Publisher Purdue University
Publication Year 2006
Sub-type Fully published paper
Editor TDR 2006 Technical committee
Start page 1
End page 22
Total pages 22
Collection year 2006
Language eng
Abstract/Summary The development of TDR for measurement of soil water content and electrical conductivity has resulted in a large shift in measurement methods for a breadth of soil and hydrological characterization efforts. TDR has also opened new possibilities for soil and plant research. Five examples show how TDR has enhanced our ability to conduct our soil- and plant-water research. (i) Oxygen is necessary for healthy root growth and plant development but quantitative evaluation of the factors controlling oxygen supply in soil depends on knowledge of the soil water content by TDR. With water content information we have modeled successfully some impact of tillage methods on oxygen supply to roots and their growth response. (ii) For field assessment of soil mechanical properties influencing crop growth, water content capability was added to two portable soil strength measuring devices; (a) A TDT (Time Domain Transmittivity)-equipped soil cone penetrometer was used to evaluate seasonal soil strengthwater content relationships. In conventional tillage systems the relationships are dynamic and achieve the more stable no-tillage relationships only relatively late in each growing season; (b) A small TDR transmission line was added to a modified sheargraph that allowed shear strength and water content to be measured simultaneously on the same sample. In addition, the conventional graphing procedure for data acquisition was converted to datalogging using strain gauges. Data acquisition rate was improved by more than a factor of three with improved data quality. (iii) How do drought tolerant plants maintain leaf water content? Non-destructive measurement of TDR water content using a flat serpentine triple wire transmission line replaces more lengthy procedures of measuring relative water content. Two challenges remain: drought-stressed leaves alter salt content, changing electrical conductivity, and drought induced changes in leaf morphology affect TDR measurements. (iv) Remote radar signals are reflected from within the first 2 cm of soil. Appropriate calibration of radar imaging for soil water content can be achieved by a parallel pair of blades separated by 8 cm, reaching 1.7 cm into soil and forming a 20 cm TDR transmission line. The correlation between apparent relative permittivity from TDR and synthetic aperture radar (SAR) backscatter coefficient was 0.57 from an airborne flyover. These five examples highlight the diversity in the application of TDR in soil and plant research.
Subjects 300100 Soil and Water Sciences
620199 Field crops not elsewhere classified
Keyword TDR
Time domain reflectometry
Time domain transmissivity (TDT)
Soil water
Soil and plant water
Soil physical behavior
Oxygen diffusion
Fidle soil strength
Cone penetration resistance
Remote sensing
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Paper ID 39

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Created: Thu, 23 Aug 2007, 22:21:13 EST