Re: SOIL SURFACE MOISTURE MEASUREMENT OR SENSING

[owner-sowacs@aqua.ccwr.ac.za]

For soil surface measurements you carn't go past tdr. Some systems come
with flat plates that can be laid on the ground to literally read the
surface soil moisture. The other way is through a pan evaporation


[Bruce comments:
My experience of measuring surface soil water content is that this is where
the variability is highest. 

There is no such thing as a uniform soil surface  (apart from a nicely
prepared seedbed), there will be changes in OM as well as vegetative matter
scattered over a surface. This small scale "unevenness" of the soil surface
must mean that uneven drying takes place.
Prodding around with probe-based sensors shows this - but care must be taken
not to mistake the sensitivity of probes that require their entire length to
be inserted with variability (as I initially did)...]
----------
>
From: owner-sowacs@aqua.ccwr.ac.za
> To: 
> Subject: SOIL SURFACE MOISTURE MEASUREMENT OR SENSING
> Date: Friday, 9 April 1999 5:27
> 
> NOTE:  To get off this list, send email to majordomo@aqua.ccwr.ac.za
> with the body of the message containing the line:
> unsubscribe sowacs
> 
> [Originally posted to IRL (apologies for cross-posting)]
> 
> "Stephen W. Smith" <swsmith@AQUAENGR.COM> writes 
> 
> List Subscribers:
> 
> We are working on a project involving the re-establishment
> of native grasses on a large Colorado site.  It is difficult
> to successfully establish native grass in this area and very
> dependent on first season precipitation.  Fortunately, we
> can apply some supplemental irrigation (via solid set,
> sideroll, or linear move sprinklers) to increase the first
> season germination success.
> 
> We expect to apply four นไ irrigations in the first two
> weeks with greater, less frequent, applications afterwards.
> A six inch total application is anticipated over 3 months.
> 
> Our water source is very, very limited and costly.  If the
> profile were deeper, as in the case of most established
> crops, we would utilize the water balance method to predict
> when to irrigate.
> 
> Are there recommendations from this group concerning soil
> moisture measurements or sensing at essentially the soil
> surface?
> 
> Thanks in advance for your response,
> 
> Stephen Smith
> Aqua Engineering, Inc.
> Fort Collins, Colorado
>