To monitoring soil moisture ([theta], [m.sup.3] [m.sup.-3]), six sets of tensiometers
were installed at the experimental area.
Monitoring Container Crop Irrigation by Means of Tensiometers
A rubber diaphragm (1 mm thick and 90 mm in diameter) was installed between two 90 mm diameter plastic flanges mounted onto the top of a tensiometer
. The underside of the diaphragm was exposed to the water and/or partial vacuum inside the tensiometer
The calibration of tensiometers
was obtained by means of four vacuum pressure (suction) values over a range of -50 to 0 kPa generated by a vacuum pump.
The results for shoulder strength measured with the tensiometer
for the hug-up test, EC test, and FC test are summarized in [Table 3].
Figure 3 shows the dependency of the dynamic contact angle to the contact line velocity for the forced spreading experiments done for two different weight ratios of mixtures of PEG/water on smooth Teflon plates using tensiometer
equipment applying the Wilhelmy plate method.
The beaker was placed on the sample platform of the Kruss K11 tensiometer
. The platinum surface tension probe was removed from the tensiometer
hook and rinsed with deionized water and dried with the blue part of the flame from the propane torch.
At these two locations, a T5x pressure transducer tensiometer
(UMS, Munich; www.ums-muc.de) was inserted to the middle of the core.
The study of the soil structure-crop yield relationship was based on the comparison between the [CE.sub.1/5] profiles, the crop yield components, tensiometer
profiles recording, and available water capacity (RU) calculations.
Here, this problem is revisited using a more accurate instrument for interfacial measurements: the spinning drop tensiometer
. The results differ considerably from the previous evaluations.
When the tensiometer
is placed against a soil surface the water in the stone equilibrates to the pore pressure in the soil.
* A gauge on the top surface of the tensiometer
that gives visual indication of the tension being applied (up to 60 foot-pounds of torque).
The moisture of the substrate may be regulated by an analogous switch tensiometer
. The pressure at the switch tensiometer
should be set between -80 and -160 hPa, regulated by a computer, depending on plant species (Frenz, 1989).
The experiments were prerformed using tensiometer
K8 (Kruss, Germany) with a 20 mm diameter platinum--iridium ring.