'Any means necessary'
From the February 2008 edition of Agriculture Today.
Waverley Ag at Burren Junction is typical of many cotton farms today seeking to increase water use efficiency in the face of drought, ground water cutbacks and zero river water allocations.
As part of a co-ordinated industry strategy, cotton growers like Andrew Greste, general Manager of Waverley Ag, have been undertaking infrastructure changes, embracing new technologies, and adopting improved irrigation management techniques.
His aim is to increase water use efficiency by 20 per cent in the next five years.
"Most cotton growers are in survival mode," Mr Greste said.
"If they are to survive they need to adopt any means necessary to improve water use efficiency."
Mr Greste has examined every component of his irrigation system, including field application, storage and distribution management.
In collaboration with research trial works conducted by CSIRO and NSW Department of Primary Industries, field application efficiencies were assessed using Irrimate technology.
Results indicated most irrigation events had excellent application efficiencies, meaning losses were generally minimal.
"The Irrimate evaluations have validated the company’s investment in increased supply channel and head ditch capacity," Mr Greste said.
"Bigger infrastructure enables us to get the water on and off quickly.
"Reduced waterlogging means greater potential yields, and increased bales per megalitre.
"While it’s good to know you are getting most of your irrigations right, the field evaluations revealed two issues.
"Our fields have higher infiltration rates early in the season, so we need to be on our guard in order to prevent over-irrigation.
"But at the end of the season water is not infiltrating to depth.
"This means we need to reduce our irrigation intervals and not let the field dry up too much," Mr Greste said.
Good irrigation scheduling is key to improving yields and water use efficiency at Waverley.
Mr Greste uses capacitance probes to monitor plant water use and apply water to fields at the right time.
To establish whole farm efficiency, he used a software package, Watertrack Optimiser last season, in conjunction with NSW DPI and Aquatech Consulting.
This allows irrigation managers to monitor water movements on the farm and identify how much water is available on a daily basis.
Watertrack enabled Mr Greste and NSW DPI to identify storage evaporation as the main contributor to farm losses.
This season the company has consolidated all farm water into a single storage and avoided wetting up non-essential channels.
It is also using electronic meters to monitor daily storage volumes.
"I can now make important management decisions with a greater degree of confidence," Mr Greste said.
Detailed seepage assessments were conducted on a number of storages.
"It’s important to know whether your storages leak.
"Seepage estimates were only two to three millimetres per day, so we can sleep easy knowing we don’t have a problem there."
Mr Greste also plans to replace a three-kilometre section of channel with one kilometre of plastic pipe.
This will be achieved by taking a more direct route from his bore to the storage.
"Evaporation in open channels can be considerable in these environments.
"I’m also looking at the feasibility of deepening a storage dam to minimise evaporative losses."
