Bankless channels increase water efficiency
GroundCover™ Issue: 111 | Author: Deanna Lush
For irrigator Dallas Stott, from Whitton, New South Wales, terraced bays with bankless channels are improving yields and water use efficiency (WUE).
Dallas, who farms with his father Peter, irrigates cereals and cotton. They have changed 1200 of their 1500 hectares from a traditional syphon layout to bankless channels.
They started the changeover in 2006 then stopped during the drought. Work kicked off again in the 2010-11 season and they have undertaken a summer program of land forming ever since.
The Stotts hosted a visit by the GRDC’s Irrigated Regional Cropping Solutions Network earlier this year because of the increasing interest in WUE and yield gains that can be made from more efficient irrigation delivery methods.
“We used to have raised beds on 1.8-metre centres with a syphon down every furrow,” Dallas says. “We always had trouble with a soil-management technique to improve lateral infiltration, called subbing. It’s quite hard, red soil, so we moved to a terraced-bay layout,” Dallas says.
The bankless channels at one end of the paddock push water up a three to four-centimetre rise to the end of the bay. Then when the bay is completely filled, the door is opened into the next bay, which is 15cm lower and starts to fill.
Dallas says the system has improved flow rates because water is held up above the next bay, effectively creating a small dam. A 5ha bay upstream of a 10ha bay take the same amount of time to water because of the increased flow rate.
“Moving into the stepped bays, we believe we’ve been given a yield increase. It varies from season to season but just being able to irrigate efficiently and sub the soils in the way they are meant to be subbed (moving water through the soil to the middle of the bed) – we are getting a gain from that. It’s a huge bonus, it’s money in the pocket.”
He says it would not be possible to do the whole farm in a year but rather strategically to choose some areas every year to focus on.
“It is quite expensive; more than $2000/ha to develop from a syphon channel layout to a bankless channel layout. Although depending on how much dirt you have to move within the bays and how big your bankless channels have to be it can be down to $1200/ha to $1400/ha.
“But it’s also about the end result you can get.”
Dallas says other benefits include thorough irrigation of the centre of the bed, which was hard to achieve with syphons, and reduced labour because syphons do not need to be handled.
“Labour-wise, it is more efficient but it is really about being able to irrigate the soil properly. It’s the best layout I’ve had here.”
He says that running the syphon layout used to require a lot of drainage and pumping, which consumed considerable fuel and electricity.
“This system now allows us to use our pumps just as supply and not so much for drainage, so they just don’t run anywhere near as much as they used to.”
Dallas says the system also gives more flexibility to rotate crops, depending on the season.
“We can flick back from a maize, soybean or a cereal crop to rice very easily if we want to.
“This system is very easy. You can change your mind from one day to the next if you want to,” Dallas says.
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A fact sheet on Irrigated wheat in the Murrumbidgee and Murray is available at: www.grdc.com.au/GRDC-FS-IrrigatedWheatNSWVic
Region South, North