Re: Watermark or gypsum blocks?

[Cliff Hignett]

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> 1. Measuring osmotic potential is notoriously difficult particularly at the
> dry end, unless you control temperature very precisely.  Would you be better
> off controlling it by placing your petri dish above a saturated salt
solution
> in a fixed temperature environment.

2. Choice of sensor shuld be by the range of potential you wish to measure.
Watermark provide good results between 50kPa and 120kPa and gypsum blocks work
between 15kPa and 600kPa.   variation between batches is acceptable for most
applications (around 10% of reading) but for research application I suggest
that
each sensor should be calibrated.
3. It may be easier to measure soil water content (many devices available - or
just weigh the pot) and then infer the matric potential from a water release
curve measured on the soil.


--
Cliff Hignett
Soil Water Solutions
45a Ormond Ave
Daw Park
South Australia 5041
pH 61 (08) 8276 7706
WWW.SOILWATER.COM.AU