ekS - Instytut Agrofizyki im. Bohdana Dobrzańskiego PAN w Lublinie ...

Through a preaugered pilot hole it can reach any depth (Fig. 62) without
destroying either the soil structure or disturbing the heat and mass transport in the
soil. For semi-permanent installation the probe can be inserted horizontally
through a sidewall of a soil pit or slantwise, from the soil surface. The probe
installed once may be left intact in the soil for as long as necessary, then drawn
out at the end of the experiment.
FP/m is a probe for in situ field measurement of the soil water content,
whereas FP/mts is its version for simultaneous measurement of water content,
temperature and salinity (electrical conductivity) of the soil from the same
sampling volume.
Both probes are suitable for periodic measurements at random and/or fixed
locations, where instantaneous profiles of water content, temperature and salinity
are to be determined by readings taken at various levels of the soil profile. Each
of them may also be applied as a mobile probe (FP/m/m or FP/mts/m) for
momentary measurements in surface layer of the soil, by walking over the field
and inserting the probe in the soil surface layer at chosen sites.
The shortest available probe is 15 cm long. Its support pipe has not any
bending. To place the probe at 5 – 15 cm depth it can be inserted horizontally
through a sidewall of a shallow soil pit. The longest possible probe is 400 cm long
(probes longer than 150 cm are delivered as a kit to be assembled by the user). In
order to install FP in the soil, a pilot hole has to be preaugered from the soil
surface, deviated out of vertical of an appropriate angle, a. The probe length, L,
and the depth, D, the sensor rods are meant to reach in the soil profile (the
installation depth) are related as follows:
D
L = − 5 + a
cosα
(89)
where: L, D and a in cm and α is the out of vertical deviation angle. The length,
L, is distance between the base of the sensor rods and the bending point of the
plastic support pipe and a is length of the part of the probe body sticking out the
soil surface. Different combinations of L, a and α allow to reach the intended
deepth, D. Suggested magnitude for a is 30°.
For the regular FP/mts the temperature sensor is fixed inside the PVC body, at
the base of the rods. If the probe is to be applied as the near surface (FP/mts/ns
presented in Fig. 63) or as the mobile, vertically inserted one (FP/mts/m), then
this base is located at the body-soil interface, where distortion of temperature
distribution is maximal. In order to avoid the problem the sensor is enclosed
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