SOWACS: SEEDS as sensors - interesting!

[Cliff Hignett]

Cliff Hignett writes to the sowacs list:
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It depends on the soil type and water content range.    If the
environment is relatively dry and the soil sandy then you might try
hydrogels (these respond to RH and soil water readily by expanding as
they take on water but you need to remove them to weigh or measure them)
- the most convenient source is the ;'pellet' blanks used by contact
lense manufacturers @ about $1 each- they are also the active ingredient
in baby diapers.

If you want a fast measure and the water content range is 0-0.3cc/cc (ie
a sandy enironment) then you could use needle size heat dissapation
probes.   these will measure the water content of a cubic mm of soil.
The technique is published but I can't find the reference - If you are
interested get in touch and I will look further.

cliff.hignett@soilwater.com.au

> Mark Bloomberg writes to the sowacs list:
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>
> My query relates to measuring moisture availability in the very small
> space around a germinating pine seed.  This environment has a
> diameter ca 1cm, is close to the soil surface and therefore moisture
> levels fluctuate rapidly in relation to time of day, changes in
> atmospheric RH etc.
>
> Oleskog & Sahlen (Oleskog,G and Sahlen K. 1999. Determination of
> moisture conditions using Pinus sylvestris (L.)  seeds as biosensors.
> Scandinavian journal of Forest Research.) stated that conventional
> methods of soil moisture measurement are not suitable because they
> may influence moisture levels in the seed's immediate environment,
> which is very small.  There are also steep vertical gradients in
> moisture in the  surface soil zone.  Oleskog opted for a bioassay
> approach, using changes in seed fresh weight as an indicator of
> moisture availability.
>
> Does anyone have alternative views on this problem?
>
> Yours sincerely, Mark
>
> Mark Bloomberg
> Lecturer in Forestry
> SPES Division, Lincoln University
> Ph (64) (3) 325 2811 Ext 8437

--
Cliff Hignett
Soil Water Solutions
45a Ormond Avenue
Daw Park
South Australia 5041
61 (08) 8276 7706
cliff.hignett@soilwater.com.au
www.soilwater.com.au




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