Australian cotton growers are reporting water savings of up to 20 per cent after redesigning their fields to do away with labour-intensive siphon irrigation.
Growers have used siphons for decades to transfer water from channels over a bank onto the crop.
Cheap and low-tech, siphons are also labour-intensive, having to be started and stopped by hand around the clock during irrigation season.
Bank-less systems remove the banks and release water in stages, getting water on and off crops quicker and providing more even watering and preventing overwatering.
“I didn’t think we’d ever get away from siphons; we’ll be going to 100 per cent bank-less as soon as we practically can,” St George grower Scott Brimblecome said.
After converting 80 per cent of his 460-hectare property to bank-less irrigation, Mr Brimblecome saved 1.5 megalitres of water per hectare.
“Once we are fully automated, I believe we can go over 2ML-a-hectare water saving — that means I can put in a winter crop if I choose or I can expand my acres and grow more cotton,” he said.
The bank-less design
Irrigation specialist Glenn Lyons pioneered bank-less design around his home base of St George 20 years ago, taking inspiration from rice paddies in the Riverina.
“Early on farmers said it wouldn’t work, they were sceptical, but one or two allowed me to design their system to get it going,” Mr Lyons said.
“For Darren Armstrong, a client at St George, going bank-less turned his worst block into his best.”
“As a guess, I’d say somewhere between 10 and 15 per cent water saving at least, maybe up to 20 per cent, and we’re growing nearly double the amount of cotton with the same amount of water,” Mr Armstrong said.
Mr Lyons warns the system does not suit every operation — it’s dependent on soil type, slope and the volume of water available.
His design is loaded onto a USB, and a GPS-guided laser on land-levelling equipment does the rest.
Costing up to $4,000 a hectare, the cost of laser levelling deters some growers.
At Sundown Pastoral’s cotton farm Keytah near Moree, fields due for regrading and maintenance were converted to bank-less first.
“We’ve increased yields by two bales a hectare, and if we can increase our yields by two bales a hectare, we can probably pay for that earthworks in two years,” Keytah general manager Nick Gillingham said.
“We’re trying to do 500 hectares a year. We’ve got 10,000 hectares of irrigated cotton here, so it’s going to take a while.
“There’ll be areas where siphons will suit better, so I don’t think we’re boots on all bank-less yet but we’re going to keep working on it.”
Chronic labour shortage
While some growers are attracted to the bank-less system by the water savings and yield increases, others are switching due to the chronic shortage of farm labourers.
Three siphon teams of eight are needed to irrigate Keytah; this year the bank-less area needed just one person.
“The irrigator could control everything on his phone, and I think that’s where things are heading,” Mr Gillingham said.
“We believe we can take the human error out of irrigating, we can be more efficient with our water use while improving yields.”
Mr Brimblecome has hundreds of siphons he does not need any more and with a laugh says he’s open to offers.
“If someone wants to hit me up for some siphons, we’ve got quite a few here to get rid of.”
Source: https://www.abc.net.au/