HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Nadler, A. Articles by Clothier, B. E. Search for Related Content PubMed Articles by Nadler, A. Articles by Clothier, B. E. GeoRef GeoRef Citation Agricola Articles by Nadler, A. Articles by Clothier, B. E. Related Collections Water Management Soil Methods/Instrumentation Structure and Properties

DIVISION S-1—SOIL PHYSICS

Horizontal and Vertical TDR Measurements of Soil Water Content and Electrical Conductivity

^a Soil and Water Institute, Agricultural Research Organization, Ministry of Agriculture, State of Israel, POB 6 Bet Dagan, Israel, 50250
^b Environmental group, HortResearch, Private bag 11-030 Palmerston North, New Zealand

* Corresponding author (vwnad{at}agri.gov.il)

When time domain reflectometry (TDR) is used to measure soil water content () and salinity, the probes can be installed either horizontally or vertically. We tested the common convention that values averaged from horizontal probes will be equal to a vertical direct measurement. In a laboratory experiment, a sandy loam soil, packed uniformly (0.02-m layers to 0.18-m depth) into a box, was gradually wetted to saturation by CaCl₂ solutions of 0, 0.5, 1.1, 2.1, 3.1, 4.5, 5.9, and 8.4 dS m^-1. Horizontal and vertical TDR probes for measuring and electrical conductivity of the bulk soil (_a) were installed during soil packing. A comparison between values averaged from three horizontal probes and from two vertical ones showed deviations of 0.02 (L L^-1). A simple water redistribution model was used to attribute this deviation to the process of averaging the horizontal results. The best practical attainable reproducibility, under our experimental conditions, were close to the theoretical limit 0.005 (L L^-1) but the average experimental reproducibility of was 0.01 to 0.02 (L L^-1). Width of the soil layer affecting the moisture measurement was reconfirmed to be close to 30 mm. The resistors-in-series model was found to be a good approximation to describe the soil profile _a from separately measured horizontal _a. Final values of the electrical conductivity of the soil solution (_w) after sufficient leaching were in good agreement with _w values calculated by an empirical protocol that uses _a, , and a soil texture property.

Abbreviations: DW, distilled water • OM, organic matter • TDR, time domain reflectometry • , soil water content • , dielectric constant • _a, electrical conductivity of bulk soil • _w, electrical conductivity of soil solution

This article has been cited by other articles:

				A. Nadler and M. T. Tyree Substituting Stem's Water Content by Electrical Conductivity for Monitoring Water Status Changes Soil Sci. Soc. Am. J., June 18, 2008; 72(4): 1006 - 1013. [Abstract] [Full Text] [PDF]

				D. Timlin, D. Fleisher, S.-H. Kim, V. Reddy, and J. Baker Evapotranspiration Measurement in Controlled Environment Chambers: A Comparison between Time Domain Reflectometry and Accumulation of Condensate from Cooling Coils Agron. J., January 1, 2007; 99(1): 166 - 173. [Abstract] [Full Text] [PDF]

				D. A. Robinson, D. A. Robinson, S. B. Jones, J. M. Wraith, D. Or, and S. P. Friedman A Review of Advances in Dielectric and Electrical Conductivity Measurement in Soils Using Time Domain Reflectometry Vadose Zone J., November 1, 2003; 2(4): 444 - 475. [Abstract] [Full Text] [PDF]