proudly sponsored by
|
archiving of SOWACS proudly sponsored by |
|
Peter Broomhall writes:
Does the Aqauflex have the capability to distinguish spatial variation in
the SMD along the ribbon length?
For example, if through some ponding on the surface (disturbed surface by
Dairy Herd) the soil moisture content for 50 % of length if 35%VSW and the
remainder at 25% VSW, do you see an average value of 30%VSW or a graph
showing the spatial differences?
If an average was given, and the full point is 30% VSW, then you may the
paddock is full. Now if you irrigate at 50 % depletion, then when a value of
15% VSW was reached you would irrigate. If Daily water use was 3 mm/day, the
in 5 days you may well expect an irrigation, however within 3 days some of
the area has already reached 50 % depletion and is stressed for 2 days
before you irrigate. Water use in this area may well drop of after reaching
50% depletion.
Now the area with 35 % VSW may well take a day or two to drain or to cease
being waterlogged, water use only being 1-2 mm per day before reaching max
potential of 3mm per day. It may well take 7 -8 days to reach 15% VSW, and
if an irrigation is applied 5 days later the deficit is too low in this area
leading to further periods of waterlogging/drainage.
Basically
first 1.5 m Second 1.5 m Average
Day 1 35% 25% 30%
2 34% 22% 28%
3 32% 19% 25.5%
4 29% 16 % 22.5%
5 26% 13% 19.5%
6 23% 11% 17%
7 20% 10% 15%
Irrigate (15% increase)
8 35% 25% 30%
Aqauflex may not give any more detail than what would be achieved with
multiple point measurements. You may still find the latter gives clearer
detail on spatial and vertical distribution.
Depending upon the percentage of area being affected by the ponding affect,
the Aquaflex may well be non-representative of the total field. A problem
already known for point measurement systems. If one big fat Bull had decided
to mate with a Cow over your ribbon, just after the ground had been softened
by rain, you may find a little ground sinkage. Just like the point
measurement systems, you may need to relocate your site.
Point measurement can be effectively used to monitor field with large
spatial variation in distribution.
I recall some work down in Tasman a few years ago ( in IAA publication).
They installed multiple Neutron probes in a Potato field irrigated with
Travelling Irrigators. They found significant variation in application
efficiency across the field. However, after three or so passes the uneven
application by the irrigator eventually achieved a uniform total amount
applied per site across the paddock.
If the Aquaflex gives a spatial distribution along the ribbon it would be an
effective diagnostic tool and interpretation may be made with confidence.
Peter Broomhall
Hortech Services Pty Ltd
a.c.n. 060 406 957
P.O. Box 370 Kallangur Qld Australia 4503
Phone/Fax :07 3886 0389
Mobile : 0418 878 484
E-mail: hortech@ats.com.au
Home Page : http://ats.com.au/~hortech