Take advantage of the autumn tickle
Using the right tool at the right time is central to the implementation of a diverse weed-control program.
In an otherwise no-till farming system, using a skim plough, harrow, rake or disc chain implement to disturb the top few centimetres of soil can stimulate an even germination of weeds that can then be controlled prior to planting the crop.
This tactic is best suited to weeds such as annual ryegrass, paradoxa grass, wild radish and fumitory, which are easily released from dormancy.
Soil type is also important, with surface disturbance tactics being considered not suitable for sandy soils, non-wetting soils and those that develop surface crusts.
The effect of soil type is two-fold. One concern is the potential increased risk for wind erosion; and the second is that the autumn tickle relies on even wetting of the topsoil.
The ideal scenario is following 20-millimetres of breaking rain on suitable soils with moderate to heavy stubble. The resulting germination of seedlings must be treated before seeding, preferably using a double-knock of glyphosate followed by paraquat, or seedbed tillage.
Shane Kelly’s family has farmed at Booleroo Central, in South Australia’s low rain zone, for about 100 years.
For the past 50 years, its focus has been on restoring the stony red-brown earth soils that had suffered from severe erosion
during the previous 50 years of farming. Shane now leases the 1000-hectare farm so he can concentrate on his engineering business, Kelly Tillage.
“Our journey with shallow-tillage implements started in the 1980s when we adopted minimum-till farming and full stubble retention to rebuild our soils and reduce water erosion risk,” he said.
“In the early days we used prickle chains to knock down the stubble, and by the early 2000s we had developed blunt disc chains for stubble mulching.
“Using the chains with clients in New South Wales, we saw they were very effective for managing summer weeds that had escaped herbicide treatment.”
The Kellys were also responding to herbicide resistance in annual ryegrass on their own farm.
Their initial strategy was to use the blunt disc chain to stimulate weed germination immediately after breaking rain in autumn, followed by a double-knock treatment ahead of seeding.
Having a large, uniform flush of weed germination results in maximum herbicide efficacy as compared with staggered germination that usually occurs after a rainfall event.
“In 2012, we developed sharp discs that can interchange with the blunt discs and be used to kill the weed seedlings, including crop volunteers, that germinate after using the blunt discs,” he said.
“We still had big swathes of ryegrass germinating because there was no suitable harvest weed seed control tool at the time. The weeds would all come up at once, and we could then reduce our reliance on knockdown herbicides by following up with the sharp discs when seeding.”
He found this strategy provided at least five or six weeks where the crop could establish in a weed-free environment.
The farm grows crops on 18-centimetre row spacing and sows at high-seeding rates to ensure crops are as competitive as possible.
“In the first few years of stubble mulching, we saw evidence of nutrient tie-up in the crop,” he said.“now the system is working well, the soil organic matter has increased and the nutrients cycle quickly.”