cotton - Greenmount Press

Irrigation
feature…
A surface irrigation trial over 14 furrows in the 2011–12
cotton season showed cotton yield improvements of 10 per cent
and water use reductions of 12 per cent using adaptive control
compared with the grower’s treatment.
The required models and data input ability have been enabled
with a software framework ‘VARIwise” created by Alison during
her PhD. VARIwise was developed to simulate and compare the
performance of alternative site-specific irrigation strategies with
user-defined, spatially variable input parameters.
The field evaluation of the VARIwise control strategies used a
Soil sensor in field to detect soil moisture and advance front.
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Visible, red and infrared images obtained using on -the-go
plant sensor.
weather station, EM38 surveys, infield soil moisture probes and
plant sensor apparatus. The plant sensor apparatus, developed
for the project, consisted of three cameras and an ultrasonic
distance sensor mounted on a trolley under a shroud and pushed
down the cotton rows.
The three cameras obtained red, infrared and visible images of
the cotton crop to estimate leaf area index, flower count and boll
count, whilst the distance sensor determined the height of the
cotton crop. These plant parameters are required to calibrate the
crop model. The cameras captured an image of the cotton every
metre along the furrow with its GPS location.
“The plant sensor I developed enables plant data to be
collected at a high spatial resolution, and in an automated control
system this is often required to determine the crop stage and
water requirements,” says Alison.
The collected field data and irrigation control strategy
determine the optimal site-specific irrigation volumes, and the
surface irrigation model (SISCO) predicts the closest achievable
surface irrigation distribution and advance trajectory.
Four advance rate sensors were installed in each furrow which
each sent a signal to the main controller when triggered by the
advance front. The main controller then compared the actual
and optimised advance trajectories and transmitted the required
control signals to the valve on each siphon to adjust the flow rate
or stop the irrigation.
“This technology is flexible in its application as it can also be
scaled up to look at groups of furrows, or alternatively to adjust
the flow rate within individual furrows.”
“Our next surface irrigation evaluation will compare the
performance of different resolutions of irrigation control.”
A research project due to commence at the NCEA by Professor
Rod Smith funded by the CRDC would see the development of
a commercial prototype smart automation system for furrow
irrigation of cotton. This would provide the automation of
irrigation application in surface irrigation systems using Rubicon
technology, which can be utilised by the VARIwise control system
when fully developed.
“Surface irrigation offers the greatest benefits for adaptive
irrigation control because this is the predominant method of
irrigation used for cotton in Australia. But the control systems can
equally be applied to pressurised or other irrigation systems.
“For example, variable-rate hardware is commercially available
for centre pivots and lateral moves. But these systems provide no
or only rudimentary decision-making support based on historical
yield or EM38 maps of the field.”
Alison’s 2012–13 cotton irrigation trial is on a centre pivot
irrigation machine in Jondaryan. The plant sensor apparatus
developed for the surface irrigation fieldwork has been adapted
to be mounted to an irrigation machine. For this trial, one span of
the irrigation machine has been instrumented with a GPS, three
plant sensors and variable-rate irrigation hardware.
This will enable a comparison of adaptive control performance
on pressurised and surface irrigation systems.
26 — The Australian Cottongrower December 2012–January 2013