Zero-till pioneers take on the plow
Fifty years ago, pioneers of zero and minimum-tillage cropping systems had a challenge convincing researchers and growers these V\VWHPV KDG EHQH¿WV RYHU D WUD ditional tractor and plough crisscrossing a paddock.
But in 2018, conservation farming methods are widely accepted across Australia.
Associate Professor David Freebairn from the Centre for Engineering in Agriculture at University of Southern Queensland is renowned for his research into the impact of cultivation on soil erosion.
He remains a go-to expert for many growers when it comes to ‘real’ advice on tactics that will improve soil moisWXUH DQG RQ IDUP SUR¿WDELOLW\
He also provided insight into the history of zero and minimum tillage in a Grains Research and Development Corporation podcast.
Prof Freebairn grew up on a farm in New South Wales where cropping country was cultivated and stubble burnt every year.
$V D XQLYHUVLW\ JUDGXDWH KLV ¿UVW research task was to assess the impact of minimising cultivation and retaining stubble on soil erosion.
He admitted to thinking ‘this won’t work’, but was amazed when rain simulators on different soils with different cover returned the same result HYHU\ WLPH ± D VLJQL¿FDQW UHGXFWLRQ LQ runoff and erosion.
Prof Freebairn has now reviewed the past 50 years of research into zero and minimum-till practices.
Since the 1960s there have been two different mindsets: the traditional method of burning stubble to reduce disease and make it easier to plant the next crop, and the idea of leaving it on the surface to protect the soil and retain water.
Catchment studies looking at water storage, erosion and runoff showed the dramatic impacts of retaining stubble.
One study demonstrated soil loss was dramatically reduced from 50 tonnes-hectare-year down to six tonnes-hectare-year if stubble was mulched, and one tonne-hectare-year if zero tillage was implemented.
Prof Freebairn said as a researcher, the challenge was to make conservation farming methods easy for growers to put into practice.
“In the early days, there were no minimum-tillage machines on the market to enable growers to plant directly into stubble, and few herbicides,” he said.
“Roundup entered the market in 1974 but cost $20 a litre, and at that time growers were using one to two litres a hectare.”
Around this time Hector Todd became one of the early growers to explore tillage and planting equipment that could handle higher stubble loads.
Machinery evaluation programs, testing equipment imported from Canada and the US, started in Queensland in the mid-1970s.
In 1968 a study, started at Warwick in south-east Queensland, provided more support for conservation-farming methods.
It showed that where there was less tillage or no tillage and stubble retained, an extra 30-50 millimetres of stored water was available to the crop in most years.
“This should have converted to extra yield, but stubble in the system resulted in poorer mineralisation of nitrogen at sowing, translating as lower protein and lower yields,” Prof Freebairn said.
“Then there was an accumulation of foliar and root diseases which got in the way of maximising the improved water capture.”
7KH ¿QGLQJ WULJJHUHG DGGLWLRQDO WULDO work and from 1968-90 researchers focused on breeding of root lesion nematode-resistant varieties.
In response to root diseases, the NSW Department of Agriculture trialled no tillage in tandem with the rotation of other crops such as sorghum and pulses, to follow a winter cereal.
“The yield response was dramatic. The extra water was used by the rotational crop, the disease pressure was less, and yields improved by half a tonne to a tonne per hectare,” Prof Freebairn said.
Improvements suit.
So, should growers fear the return of cultivation nowadays?
“The occasional working of a notillage paddock might trigger the germination of weed seeds, but it won’t destroy 10 years of hard work,” Prof Freebairn said.
“I have reviewed 50 years of conservation farming, and I now advise any growers who are still sceptical about this concept to start small and experiment.”
To listen to Prof Freebairn’s podcast, visit website https://grdc.com. au/podcasts. in machinery followed