Carole,
The disturbance to the soil structure around a well
installed neutron probe access tube should be minimal
if the correct installation method is used. The large
volume of measurement of the N probe, also means that
any disturbed zone is proportionally less important
than for eg capacitance sensors in tubes. The
electromagnetic field of the latter does not penetrate
far into the soil - and measures exactly in the most
disturbed zone!
The disturbance around a neutron probe tube will be
far less than around most other types of sensor,
especially if a hole has be dug. This can seriously
disturb the flow paths in the soil. For the plough
layer in agricultural soils, this may be tolerable,
but to greater depths (eg 1 - 2m or more), then
digging holes for sensor installation is a big and
very soil disturbing job.
Martin Hodnett
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