Sweet pea-sorghum rotation on Darling Downs
GroundCover™ Issue: 25
Summer sorghum and winter chickpeas have proved a sweet rotation for Chris and Sue Hornick, of Cecil Plains, who farm around 1,000 hectares of "light Condamine clay soils" on Queensland's Darling Downs.
Chickpea is zero-tilled into standing sorghum stubble, which provides the soil protection chickpea is criticised for lacking. In turn the chickpea leaves residual nitrogen for the following sorghum crop.
Sorghum is sprayed out pre-harvest with a high clearance coupe, allowing harvest up to two weeks earlier while conserving moisture and reducing lodging.
And, as an added bonus, Mr Hornick says the standing sorghum stalks "cushion" the chickpea grain as it flows through the header, reducing any cracking problem.
What nitrogen bill?
"We can back up a 5 t/ha sorghum crop with chickpea at 1.9 t/ha, and the chickpea has carried over as much as 100 units of N/ha a year; our nitrogen bill is negligible," Mr Hornick says.
"We have no fixed rotation, other than that I always try to follow grain crops with a legume, and chickpea is a big part of that. You can plant them without a lot of moisture and they can be sown direct after sorghum.
"We have tried pigeon pea, mung beans and faba beans but, of all of them, chickpea is where the market has now stabilised." Double-cropping wherever possible meets the Hornicks' target of more than 100 per cent production off the given farm area every year, a target they say has to be achieved to meet commitments on leased country.
Sorghum stays viable on better soils
While dryland cotton is tending to replace sorghum on better soils across the GRDC's northern region, Mr Hornick says the summer grain remains a very reliable crop on the Darling Downs, given the right treatment.
His sorghum crops average around 5 t/ha; his best yield ever — 10 t/ha crowned as reserve champ Toowoomba Royal Show field crop competition — was achieved during drought.
"I soil-test after chickpea crops and usually find around 40 units of N after a normal crop of 1.9 t/ha," he says. "In 1997 the chickpea didn't do very well, only 1 t/ha, but it carried over 100 units of N; it had established a good plant growth before it failed."
The Hornicks have 12 years' experience with chickpea. This winter they have 360 hectares under the desi varieties Norwin and Barwon on ground equally out of cotton and sorghum. While the Hornicks irrigate cotton, "we don't irrigate chickpeas because the country here at home isn't level enough and chickpeas don't like waterlogging," Mr Hornick says.
Support for downhill controlled traffic
"We are working towards controlled-traffic farming, with 2-metre beds, and we think the new idea of running the tracks up and downhill will benefit chickpea in a big way.
"Downhill tracks will get the water away from the chickpea plants, and will also let us fit the crop into areas where we have not grown it before.
"We do some strip-cropping on the home place and all paddocks are cropped to suit the direction of water flow"
Heliothis management a trial
Like other Darling Downs farmers, Mr Hornick is grappling with problems of heliothis management in an area whose cropping mix provides the insects with a moveable feast from spring through autumn.
Last year, for instance, his chickpea crop dried out halfway through flowering and then reinvigorated after a fall of rain; he had to spray twice.
Then, instead of zero-tilling, he needed to plough down the chickpea stubble to 'pupae bust' heliothis, and that was extra cost.
Emerging herbicide resistance — particularly in sowthistle — is a weed control worry in chickpea, with available chemicals 'useful but expensive' and the option of cultivation in 90 cm rows ruled out where chickpea is zero-tilled into standing sorghum stubble.