Optimum seedling moisture content..

[Y.H.deHaan]

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Haan, Y.H. de writes:

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In relation to the measuring problem. I would try a mini tensiometer (porous
cup) it really measures the hydraulic head. 

In relation to improve the problem of drying. I would use some fines (like
clay or organic materials) to add to the seedling soil mixture. They hold
the water to a much higher suction. Drying of the seedling will not appear
if the soil is still moist.
        -----Original Message-----
        From:   owner-sowacs@aqua.ccwr.ac.za
[SMTP:owner-sowacs@aqua.ccwr.ac.za]
        Sent:   Wednesday, February 20, 2002 11-14
        To:     Y.H.deHaan@CiTG.TUDelft.NL
        Subject:        Optimum seedling moisture content..

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        In relation to measuring water content when much of the water is
tied up
        in granules.   I know conventional TDR will not work - it does not 
        recognise the water in the granules when the water in the medium as
a 
        whole has drained to the point where there is no continuous film.
I 
        suspect heat dissapation sensors will not work for the same reason. 
        One brand of capacitive sensor DID work.   This is not a trivial
problem 
        - I would suggest using gravimetric techniques.

        A related comment.    It is a good idea to check the moisture
release 
        curve of the poly acrilimide. Many of these materials do not release

        water until they are at close to wilting point - far to dry to do 
        vegetables any good.

        Cliff.hignett@soilwater.com.au

        owner-sowacs@aqua.ccwr.ac.za wrote:

        > I would like some information on the ideal moisture for seedling
germination.
        > 
        > Tomato and peppers. 
        > 
        > Also which probe would you recommend. 
        > 
        > I am a chemist and am interested in experimenting on optimising
growing conditions for seedling germination.
        > 
        > I am using poly acrylamide water retention granules at about 1%
%v/v
        > 
        > Can you help
        > 
        > Bernard Irving   <bernardirving@hotmail.com>
        > 
        > [Bruce comments
        > Assuming these are potted plants, the sensor probe would need to
be small
        > enough to insert into the pot without disturbing the roots too
much,
        > and provide a volumetric readout.
        > Please provide more information on the application.
        > I wonder if anyone can comment on the effect of water retention
        > granules on measured water content?!
        > 
        > I am sure the various manufacturers will also contact you
directly.
        > Bruce]
        > 

        -- 
        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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