EDP Sciences Journals List
Home Document
Subscriber Authentication Point
Issue Agron. Sustain. Dev.
Volume 24, Number 5, July-August 2004
Page(s) 275 - 279
DOI 10.1051/agro:2004023

Agronomie 24 (2004) 275-279
DOI: 10.1051/agro:2004023

Control of the moisture content of growing media by time domain reflectometry (TDR)

Philippe Morel and Jean-Charles Michel

UMR A 462 SAGAH (Sciences Agronomiques Appliquées à l'Horticulture), INRA-INH-Université d'Angers, 42 rue Georges Morel, BP 57, 49171 Beaucouzé Cedex, France

(Received 24 June 2003; accepted 7 May 2004)

Abstract - The irrigation of pot crops requires considerable follow-up because the autonomy of the water reserve of the growing medium is low in relation to plant water requirements. Computerised systems for irrigation management are therefore under investigation. Time domain reflectometry (TDR) was used on different peat-based mixtures to which perlite or composted bark were added in volumetric ratios of 0, 25, 50, 75 and 100%. Calibration equations (linear or polynomial) established between the water content and dielectric constant were obtained for each mixture. Their precision is highly satisfactory (R2 > 0.95), except for the mixture with 100% perlite. However, this method requires an equation per growing medium. We therefore attempted to establish a general formula that could be applied to binary peat-based mixtures. We tested second-order polynomial calibration equations, a function of the dielectric constant measured as well as the volume percent of complementary material added to the peat (bark or perlite). The precision of these equations is excellent for all mixtures (R2 > 0.96). For all practical purposes, this approach would considerably simplify the use of TDR for computerised irrigation management because it would introduce only a limited number of parametric equations into the irrigation system.


Key words: irrigation management / TDR / pot crop / growing medium

Corresponding author: Philippe Morel morel@angers.inra.fr

© INRA, EDP Sciences 2004


What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.