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Those not on Agromet-l will have missed this interesting
perspective on soil water content : temperature assessment.
Bruce Metelerkamp
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From: Fabio Micale (micale)
To: agromet-L@mailserv.fao.org
Date: Tuesday, January 7, 1997 1:03 pm
Subject: Soil heat flux and soil moisture
Hello all,
I know that exit a strong relation between soil thermal
properties (conductivity, diffusivity) and soil moisture content.
Now, somebody could tell me if exist the possibility to know
(calculate) the soil moisture content when I have soil
temperature at different level (surface, -10 cm, -30 cm) and I
know its composition (organic matter, sand, loam, etc.)?
Tank you in advance, and the best wish for new year.
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-.o00--(_)--00o.---------------------------------------
Fabio Micale, Ph.D. |voice: +39-79-258600 |
Servizio Agrometeorologico |fax: +39-79-262681 |
Regionale per la Sardegna |http://www.sar.sardegna.it|
V.le Porto Torres, 119 | |
Sassari (Italy) - 07100 |micale@sar.sardegna.it |
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========================================================= From: Gommes, Rene (SDRN) (Rene.Gommes@fao.org)
To: agromet-L@mailserv.fao.org
Date: Tuesday, January 7, 1997 3:13 pm
Subject: RE: Soil heat flux and soil moisture
If you have continuous records of air and soil temperatures at
various depths, it is indeed possible to compute heat capacity
and thermal conductivity, BUT rainfall has a temperature which is
different from that of soil water, which creates problems in
practice.
In addition, the heat capacity as a function of soil moisture,
goes through a maximum, which makes it sometimes difficult to
know on which side of the maximum you are.
I tried to use that method to determine the beginning of the
cropping season. My reasoning was that in climates with a marked
dry season (say in Central Tanzania), you are sure that soil
moisture is virtually zero in November when the season starts, so
that you know that you are on the left of the maximum. In
practice. Because of the problem of the temperature of rainfall,
things turned out to be too difficult to be used operationally.
I used to derive the thermal properties from the temperature
curves. Maybe better results can be achieved if you can compute
the thermal properties of "dry" soil from the soil composition,
if you can make some reasonable assumptions about the temperature
of rainfall and infiltration rates...?
Good luck, and let us know your final conclusions!
R.
=============================================================
From: Nachtergaele, Freddy (Freddy.Nachtergaele@fao.org)
To: Agromet-L@mailserv.fao.org
Date: Tuesday, January 7, 1997 5:42 pm
Subject: FW: Soil Moisture content and temperature
>From: Nachtergaele, Freddy (AGLS)
>To: Micale, Fabio
>Cc: AGL-Registry; Tiddi, AnnaPaola (AGLS); Gommes, Rene (SDRN)
>Subject: Soil Moisture content and temperature
>Date: 7 January 1997 14:37
>
>Dear Dr. Micale,
>
>Soil moisture content is obviously determined by more factors
>than mentioned in your e-mail (rainfall and soil moisture
>storage capacity for instance). Soil moisture storage capacity
>can be derived (with relatively low levels of confidence) from
>clay%, organic matter%, bulk density and clay mineralogy. The
>state of the art in this respect was recently well summarized
>by N. Batjes from ISRIC Wageningen in an article in Geoderma:
>"Development of a world data set of soil water retention
>properties using pedotransfer rules "(Geoderma 71 (1996)
>pp31-52). For the specific influence of Soil heat on the
>moisture balance an excellent summary is contained in "A review
>of soil factors and processes that control fluxes of heat,
>moisture and greenhouse gases" published by ISRIC as WISE
>Report no3, Technical paper 23. An expert in this field worth
>contacting is Dr H.R Oliver from the institute of Hydrology,
>Wallingford UK. For more info on these references you could
>contact Mr Batjes at: batjes@isric.nl
>
>With best regards,
>
>Freddy Nachtergaele
>Technical Officer Soil Resources
>AGLS FAO Rome
>