Relying on rain
Inside a diverse cropping operation at Dalby
IN 1904, the Dalby town council and their subterranean drilling team were overjoyed when, at
870m, they struck water. The small Queensland town was looking to establish an artesian bore similar to other nearby centres such as Moree and Mitchell, and what they struck was mineral-rich and a therapeutic 38C.
For the next 34 years Dalby was a place where locals and tourists indulged in “taking the waters” – a national health fad in the early 1900s that was thought to be remedy bodily aches and pains.
But for Dalby farmer Wayne Newton, “taking the waters” is not about drilling down, but rather intercepting water to fill dams – something that has been in short supply in recent years.
With no access to bore water or allocations from the Condamine River, he can only use what comes from the sky.
Much needed October rainfall of about 100mm has temporarily quenched the thirsty soils where he farms on the Darling Downs flood plains, 200km northwest of Brisbane.
Annual rainfall totals have been well down almost every season since 2013, with
50mm cracks frequently seen in the heavy clay soil.
Wayne said although the cracks could be a metre deep and looked severe, they were a normal function of the expansive Vertosol clay soil. He just needs them to fill with water.
“The beauty of it is when you get heavy rain the cracks literally fill from the bottom,” he said. “The water runs down to the bottom of the cracks and soaks out into the ground in between the cracks – it’s like filling a bottle from the top.”
“When the soil gets wet it swells and the cracks close. It swells both vertically and horizontally and everything closes up, and that helps then keep the moisture in the ground until the crop uses it, and once the crop uses it the cracks open up again ready to take in the next rain.”
WAYNE puts in both summer and winter crops, but says the most important are the summer rotations of cotton, sorghum, mungbeans and maize.
Being in a subtropical climate means croppers on the Downs are less reliant on in-season rain, but need to have soil water profiles relatively full before sowing.
The area’s heaviest clay soils store up to 250mm of plant available water, with the lighter ones closer to 200mm.
To shore up water supply for thirsty crops like cotton, the Newtons built two 1000-megalitre turkey-nest dams in the late 1990s.
The compacted clay-wall dams store water that is “harvested” from natural drainage lines running across their property. The water is intercepted as it runs across the flats toward the Condamine river, and pumped into the dams.
There is now a moratorium on infrastructure intercepting water this way, under the Murray Darling Basin Plan.
“When it comes to overland flow, because we’re limited to when we have the water, we can do it – it’s not like we’re taking it out of a river – there’s may be only four or five days a year we can pump it,” Wayne said.
In order for the water to run, the cracks in the clay must fill up first.
“When things are reasonably dry mostly we don’t see much run-off until we’ve had over 100mm rain,” he said. “At the 100mm point there’s a bit of water starting to lie around on the country. Once you get another storm with another 25–40mm that’s when you start to see the water running, and that’s what we’re seeing now.”
PUMP IT UP
ONCE the water is running, the Newtons can pump 200 megalitres of overland floodwater a day, meaning that five days of pumping will fill the dams for the next season.
Of their 630mm average rainfall, well over half comes in summer.
“It’s a highly variable climate we work in, and the distribution of that rain can be quite sporadic,” Wayne said.
“Certainly it’s not unusual to go through July to September with very little or no rain.
“We take rain when we can get it.
“Building storages for water is just one of our responses to the climate we have up here.”
Storm cells in summer were unpredictable and area-specific, the multigenerational farmer said.
“There might be a big storm travel through the district, and if you’re right underneath it you get the rain, and if you’re on the edge you smell the rain.
“Over the years I’ve seen seven inches come down in a couple of hours. Well that makes a lot of water.”
Despite getting too much rain being a more common problem than the opposite, the past few years have been exceptionally dry.
Until mid-October, Dalby has hardly seen enough rain to fill the cracks, let alone the dams. The area recorded
42mm in the normally wet months of March to May, and
72mm between February and October.
But a lot can change in three weeks. The skies opened in early October, dumping 105mm. At the Newtons’ place the clay cracks filled quickly, but only small amount of run-off was captured for storage.
According to Wayne, their two dams are now 15 per cent and 75 per cent full, meaning more summer rain is needed for the summer crops.
It’s a highly variable we work in, and the distribution of that rain can be quite sporadic.
— Wayne Newton
WATER, weather, prices and a myriad of other factors mean that deciding cropping rotations in the subtropical climate can go down to the wire.
“We don’t have fixed rotations, we’re very flexible. What we plant is driven firstly by available moisture, and then what the returns are going to be,” Wayne said. “Cotton is one of our most profitable crops, but then you’ve got to have a good profile of moisture if you want to grow it on dry land, or irrigation water if you’re going full irrigation.”
Cotton is now making good returns for Australian farmers, and the Newtons are well serviced by three local cotton gins to process their harvest.
In a good year they can produce several thousand bales, with the yield varying from three to eight bales/ha on dryland paddocks and 10-12 bales on irrigated ones.
“Cotton prices are pretty good at the moment – they’re north of $600/bale. That’s good. We’ve sold cotton for as low as $300/bale before, but anything above $500 is reasonable,” Wayne said.
Having water security for the cotton-growing season is paramount, meaning the storage dam levels at early November are crucial when deciding how much to put in.
Sowing is anywhere between October and December.
This year Wayne, who farms with his wife Bev, son Greg and daughter-in-law Lisa, has put in 320ha, with the October rain coming in the nick of time to encourage a larger planting.
In the Darling Downs region cotton isn’t taken off until April-May, but in the interim sorghum and mungbean crops are harvested.
“The beauty of the long growing season means that if it has a tough start, cotton is such a tough plant and it can hang on for rain later in the summer. The subsoil moisture keeps it going and then if you get the rain, you get the yield,” Wayne said.
Underpinning their cropping schedule is sorghum, this year the Newtons aim to put in up to 800ha.
WORKING SMARTER: Dalby grain grower Wayne Newton is a Farmer of the Year nominee.
Wayne Newton holding chick peas.
A flock of emus on Wayne Newton’s family property at Ranges Bridge 240km west of Brisbane.
RAIN DANCE: Dalby graingrower Wayne Newton on his property 240km west of Brisbane.
Mr Newton said deciding cropping rotations in the subtropical climate can go down to the wire.
This year the Newtons will plant 800ha of sorghum and 320ha of cotton.
Emus wandering the paddocks on the Newtons’ property.
Chickpeas are part of the Newtons’ winter rotation.