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November 2015
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Natural resources and energy
Special
Average irrigation yields improved
with variable rate irrigation systems
S
oil and topography varies in most centre pivot circles with
some soil types and areas that will become water locked
while others will remain too dry to produce optimally. Due
to this, the yield will also fluctuate. These low and high spots
and soils create the need to vary water applications.
Variable rate irrigation technology allows you to apply exactly
the right amount of water to specific areas under your irrigator
− giving full control to maximise yields and profitability. The
Growsmart precision variable rate irrigation system achieves this by
individually pulsing sprinklers on and off, while also controlling the
irrigator speed to modify the application depth along the length of
the irrigator.
Control of the irrigator speed and individual valves allows the
amount of water applied to each area to be carefully regulated, opti-
mising water application.
There are many agricultural applications where irrigation efficien-
cy can be improved through the use of variable rate irrigation. The
technology has proven benefits for farms irrigating over varying soil
types or with different crops planted under the one irrigator. Water
savings and yield increases are achievable by reducing irrigation to
high run-off areas and low areas prone to getting wet and boggy.
Irrigation can also be completely avoided over buildings, tracks,
roads, water-ways, non-productive and environmentally sensitive areas.
First commercialised in 2008, Growsmart precision variable rate
irrigation was the industry’s first true precision variable irrigation
system. Growers have reported many advantages achieved from in-
stalling the system, including record crop yields, increased pasture
production, significant irrigation water savings, a drop in the power
bill due to reduced energy requirements and reduced maintenance
costs of farm tracks and lanes.
Independent research has indicated that in any one year, variable
rate irrigation can save between 9% and 26% of irrigation water. In
practise producers in Australasia have been achieving water sav-
ings of up to 35% by tailoring irrigation to the water requirements
of variable soils underneath an irrigator. These savings are possible
through the use of the intelligent precision variable rate irrigation
system enabling application rates over wet areas to be reduced and
water completely turned off over tracks, drains, buildings and unpro-
ductive areas.
Furthermore, because the precision variable rate irrigation system
only delivers water when and where it’s programmed to, there are
no wasted pumping costs. Calculations show that 9% to 26% water
savings equates to 27 kg - 77 kg of CO
2
-eq/ha/yr energy savings.
Rather than farming to the limitations of an existing irrigation sys-
tem, several crops that require varying amounts of water can be
grown under the one irrigation system when variable rate irrigation
is installed, giving you the ability to maximise the yields of each
crop. Fertiliser and chemicals can also be efficiently applied exactly
where they’re needed with the pinpoint accuracy of precision vari-
able rate irrigation technology which can be a real saving compared
to blanket applications.
Precision variable rate irrigation solves common over-watering is-
sues inherent to many machine set-ups such as laterals, geo-laterals
and part circles. For instance, irrigation plans can be set up to ramp
down application rates when approaching the reversing point for a
part circle or lateral and then ramp up again when heading away
from the barricade. The intelligent system can also detect when a
geo-lateral changes from lateral to pivot mode, altering the sprinkler
rates accordingly to even out the application.
Irrigation plans are created with FieldMAP, precision variable rate
irrigation’s custom mapping programme. The software is preload-
ed with applicable irrigator data, and then it is customised for each
system after which it is ready to generate irrigation plans. Water
application can be optimised for both the area irrigated and the
JACO NEL,
technology and field service manager: Lindsay
Figure 1: Irrigation plans are easily created with the map-based
FieldMAP software.