Application examples
 

    Crop Water Uptake Studies

Researchers at the University of Reading are developing new techniques for studying the diurnal patterns of water uptake and water efflux from roots. Soil water content was measured using ThetaProbes which were well suited for this purpose because of their thermal stability and high resolution. One investigation looked at the temporal and spatial patterns of root water dynamics in maize/sunflower intercrops. This was part of a broader detailed study of interspecies competition for water and light.  

Further work compared the overall rates of water uptake by the maize and sunflower crops with their rates of transpiration. Measurements were made using sap flow gauges and also derived from readings taken at various points in the canopy using an AP4 porometer.

 
An environmental monitoring system, built around the DL2e Data Logger, has been installed at a site in Saxony (Germany), under the control of the Institution for Environmental and Geological Sciences, Saxony. The installation includes 15 tensiometers, 10 ThetaProbes, 1 Equitensiometer, 5 soil temperature probes, 2 air temperature and RH probes, 2 wind speed sensors, a wind direction sensor and an albedometer. Power is provided from a 55W solar panel and 140Ah battery. The pump, logger, controller, motors and valves are housed in a large weatherproof enclosure - as shown in the photograph. This site is one of four in the region, all collecting similar data. 

Three soil water samples are collected automatically at 5 different depths, the lowest being 160cm. Tensiometer readings are used to regulate the level of vacuum at a constant -20 kPa below the soil water potential reading. The data and samples are collected every 4 weeks, and the soil water is then analysed for minerals, heavy metals and organo-chlorides. 

With thanks to UP Umweltanalytische Produkte gmbh, Delta-T’s distributor in Germany, for providing this example.

Delta-T's new catalogue:   covering:
Soil Water Content: ThetaProbe -   introduction ;   performance ;   theory
Soil Water Potential: Tensiometer ;   Equitensiometer
Pore water conductivity: Sigmaprobe     theory
Evapotranspiration: (Software and weather stations)
Data loggers and readout units ;   Application examples ;  


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© Bruce Metelerkamp

www.sowacs.com/feature/deltat/water-uptake.html
last update : 14 August 1999