Making the most of variable weather
GroundCover™ Issue: 21
Farmers on Queensland's Darling Downs and in northern NSW are conducting a 'do-or-die' cropping systems experiment. This has been dictated by the drought conditions of the past five years.
The outcomes have been astounding yield results under dry conditions. The secret to success: minimum tillage and stubble retention, which keep maximum soil, water and nutrients on-farm, together with gauging stored soil-water as a preplanting necessity.
These conservation farming elements have been combined with an understanding of when and where to double-crop to gain the most from available moisture storages and summer storms.
"Water-use efficiency means farmers can double their yield for no extra cost," said Mike Burgis, Program Director of Conservation Farmers Inc. "An extra 25 mm of water available to the crop means 250 kg/ha more yield."
Conservation Farmers, with 400-500 members in the northern grains region, is a farmer-led crop improvement group formed in the early 1980s. It has spurred big changes in the way soil is conserved and water managed on the Darling Downs.
Mr Burgis estimates that about half the growers on the Downs now use conservation methods. Experience has shown that, for instance, 30 per cent stubble cover gives about 70 per cent protection from erosion during heavy storms — which is frequently how the rain comes down.
One of the founding members, Nev Ronnfeldt, farms with his son Garry on some 1,360 hectares of black soils on the treeless Jimbour Plain. "Back in the
'70s," he says, "I used to see the water run off into the creek, so it wasn't available for planting. I must admit there was a bit of erosion, but I didn't see that at the time because I had blinkers on.
"Five years of drought have taught us a lot of management skills. Anyone who didn't adapt isn't around anymore."
He's developed minimum tillage methods (one-pass or zero-till) to suit his soil, the weed burden and rotations and says there are "dozens of ways" to handle stubble so it's not a planting barrier. He uses a double-disk Kinze-type opener for summer planting after wheat. Harvesting low is an important strategy.
Skip-row planting increases available water.
During the drought he and his family have focused on sorghum, cotton and wheat rotations — opportunity cropping according to the dictates of stored soil moisture.
"In the second year of the drought the only successful sorghum crop we had (harvesting 2.5 t/ha) was the skip-row planting."
Mr Ronnfeldt doesn't think there's such a thing as a normal season. So every crop becomes an 'opportunity paddock'. With proper nutrition and onservation management the system is as sustainable as the soil-water harvest. "All yields are related to soil moisture," he says.
He sees opportunity cropping as a mirror of natural vegetation response to variable moisture. In other words, you store as much soil-water as possible and grow plants when the water is adequate.
The stored soil moisture is the baseline for decision-making. Mr Ronnfeldt says a summer storm or two can usually be expected to top it up in that part of the rotation. Global positioning systems can be used to pinpoint the relationship between soil moisture and yield.
Wheat as a soil conditioner and mulch
If there is a good planting rain after the cotton harvest the Ronnfeldts use a one-pass operation to plant a percentage of their cotton ground back to wheat, with the prime purpose of getting stubble on the soil before the summer storms.
In 1996 the wheat after cotton yielded 2 t/ha. Rain damaged the double-cropped wheat last year, but Mr Ronnfeldt says he is not too concerned about making milling grade since there is a good price on the local market for feed wheat and the wheat stubble is a valuable soil cover.
"We let the stubble stand as long as possible and when we knock it down it disappears fairly quickly," he said. This and the earthworms indicate a biologically active soil.
"We never saw earthworms under conventional farming systems but in the first year of no-till we found masses of worms around the tines at sowing and it's been like that since."
With evidence of declining fertility and soil loss due to erosion on the Downs, Mr Ronnfeldt has this comment: "You can wait for the 100-year flood event that shifts lots of soil to the plain, or you can manage the soil you have."
Contact: Mr Nev Ronnfeldt ph/fax 07 4663 9743
Region North, South, West