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>Moshe Meron wrote: > Add to this the natural variability in soil water content, and soil water potential on the micro-scale in the soil. For instance lately obtained (and not yet published) results by Martin Shmitz from the FAL-Braunshweig, Germany, (SCHMITZ@BT.FAL.DE) showed similar, and quite sizable, variability for TDR, FDR and granular matrix sensors readings in a very small grass plot. Common to all of those sensors was the measurement of a very small soil volume. It looks like the key of useful soil water content / potential measurements is at large volume measuring devices, or alternatively at numerous (and cheap...) small soil volume measuring sensors. There is still some place for technological advances in soil water measurement. <<<< This is one component of sensor development that will always be argued - does the improved resolution offered by developing techniques (for example dielectric techniques compared to nuclear), improve measurement. If many readings are taken (for example multiplexing of TDR or FD sensors) then the smaller volume of measurement is acceptable and indeed an understanding of the variability can be obtained. However, if few readings are obtained due to cost or ability, then a larger integrated volume of measurement will offer a more robust indication of the soil conditions. The argument is circular, I suggest that the reasoning behind obtaining the measurements is more important and once this is understood, (generally) the instrumentation pretty much sorts itself out. Brendan George Research Officer Forest Research & Development Division State Forests of NSW PO Box 100 Beecroft 2119 Australia +61 2 9872 0111 (ph) +61 2 9871 6941 brendang@sf.nsw.gov.au