Abstract

A new sensor for the measurement of electrical conductivity (EC) and moisture content, specifically designed for soilless substrates, has been released (GS3, Decagon Devices). The Hilhorst equation has been proposed as a tool to convert the measured bulk EC (ECb) into the pore EC (ECp, the EC of the solution in the pore spaces of the substrate). A test was carried out to verify the ability of the GS3 sensors to measure changes in the substrate EC under realistic cultivation conditions. Pots, containing tomato plants growing in perlite, were subjected to irrigation for about four weeks with a schedule set to have a leaching fraction of about 90%, which enabled the maintenance of very similar EC in both the root zone and the drainage solutions. A low and a high EC nutrient solution (EC = 2.4 and 4.1 dS/m, respectively) were used in the first and the second half of the test, respectively. The EC of the leachate, used as a measure of the real substrate ECp (ECpreal), the ECb measured by the GS3 sensors and the resulting ECp calculated with the Hilhorst equation (ECpHilhorst) were recorded during the test. The three parameters (ECb, ECpreal and ECpHilhorst) all showed the trend of increasing salinity in the substrate. However, both ECb and ECpHilhorst resulted in different values, in absolute terms, compared to the ECpreal provided by the measurement of the leachate. In particular, the ECpHilhorst values were always lower than ECpreal (0.60 vs 2.48 dS/m and 1.10 vs 4.68 dS/m, on average, respectively in the first and second half of the test).However, the ECpHilhorst was correlated in the tested EC range with the real ECp in the substrate (ECpreal = 4.2815×ECpHilhorst - 0.0766, R2=0.99). According to our results, it seems that GS3 sensors used in perlite are not able to provide accurate values of ECp simply by applying the Hilhorst equation. However, the values provided by the sensor are correlated with the real ECp of the substrate; therefore, using a proper second-step equation can help to convert the obtained value into the real ECp of the substrate.

Autore Pugliese

• Parente Angelo , Montesano Francesco Fabiano

Tutti gli autori

• F.F. Montesano; M.W. van Iersel; A. Parente

Titolo volume/Rivista

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Anno di pubblicazione

2015

ISSN

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ISBN

2-85352-549-X

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