WP4C
Soil water potential lab instrumentation
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Studying the extreme water status of soil has never been performed...WP4C can do it!
Soil hydrology
This bench-top instrument has allowed great advances in the field of water status measurements of porous media. In my experience within the Agro-Hydrological Sensing and Modelling laboratory (AgrHySMo, www.agrhysmo.agr.unipi.it), the instrument has broadened the explored domain of soil water potentials. Potentials were usually measured with a pressurized method (e.g. Richards' chamber), which had safety limits (similar to bombs) and lower measurement range (up to 2.5 MPa). The WP4C allows exploring the response of the crop to the extreme conditions of soil water deficit, which has never done before. Concerning the laboratory protocol to determine the soil water retention curve, the time for each measurement has improved markedly: a few hours for each point of the curve repeated 10 times in precision mode. Safety has also been improved compared to pressiometric methods. Recently, I have also used the device to quantify the water activity in food (maize kernel) with the aim of studying the growth conditions of the fungi producing mycotoxins. In this context, the support of the meter group team was very useful, which allowed me to adapt the instrument to this type of measurement.
Review Date: 23 Jun 2020 | METER
Studying the extreme water status of soil has never been performed...WP4C can do it!
Determination of the soil water retention curve
This bench-top instrument has allowed great advances in the field of water status measurements of porous media. In my experience within the Agro-Hydrological Sensing and Modelling laboratory (AgrHySMo, www.agrhysmo.agr.unipi.it), the instrument has broadened the explored domain of soil water potentials. Potentials were usually measured with a pressurized method (e.g. Richards' chamber), which had safety limits (similar to bombs) and lower measurement range (up to 2.5 MPa). The WP4C allows exploring the response of the crop to the extreme conditions of soil water deficit, which has never done before. Concerning the laboratory protocol to determinate the soil water retention curve, the time for each measurement has improved markedly: a few hours for each point of the curve repeated 10 times in precision mode. Safety has also been improved compared to pressiometric methods. Recently, I have also used the device to quantify the water activity food (maize kernel) with the aim of studying the growth conditions of the fungi producing mycotoxins. In this context, the support of the meter group team was very useful, which allowed me to adapt the instrument to this type of measurement.
Review Date: 2 Jun 2020 | METER
Water potential measurement
The WP4C is a complex instrument due to its versatility, but extremely easy to use with sample sizes up to 7 ml. Simply fill half of the cup with soil, leaves or seeds, and then equilibrate the sample.
The dew point sensor inside the WP4C is a primary measure of water potential, not some secondary parameter merely correlated with water potential. It measures the combined matric and osmotic potential using fundamental thermodynamics and a finely-tuned calibration.
Here’s how it works:
The WP4C determines the relative humidity of the air above a sample in a sealed chamber (conforms to ASTM D6836). Once the sample comes into equilibrium with the vapor, relative humidity is determined using the chilled mirror method. This involves chilling a tiny mirror until dew starts to form. At the dew point, the WP4C measures both mirror and sample temperature within 0.001 °C. This allows for unparalleled accuracy in the -0.1 MPa to -300 MPa range so you can have full confidence in sample readings.
