Fifty years ago, the pioneers of zero and minimum tillage cropping systems had a challenging time convincing researchers and growers that these systems had benefits over a traditional tractor and plough criss-crossing a paddock, but in 2018 conservation farming methods are widely accepted across Australia.
This week’s guest on the Grains Research and Development Corporation (GRDC) podcast series is Associate Professor David Freebairn from the Centre for Engineering in Agriculture at the University of Southern Queensland (USQ).
Professor Freebairn is well known across eastern Australia for his research into the impact of cultivation on soil erosion and remains the go-to expert for many growers when it comes to ‘real’ advice on tactics that will improve soil moisture and on-farm profitability.
In this week’s engaging podcast he shares his insights into the history of zero and minimum tillage and the early opposition the practice faced from growers and his fellow researchers.
The podcast is part of a series developed by the GRDC to keep growers and other industry stakeholders informed. The series features some of the grains sector’s most well-known researchers, growers, advisers and industry stakeholders sharing everything from the latest seasonal issues, to ground-breaking research and trial results with on-farm application.
Prof Freebairn grew up on a farm in New South Wales where cropping country was cultivated and stubble burnt every year.
As a university graduate, his first research task was to assess the impact of minimising cultivation and retaining stubble on soil erosion.
He admits to thinking ‘this won’t work’, but was amazed when rainfall simulators on different soils with different cover returned the same result every time – a significant reduction in 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 quite early the dramatic impacts of retaining stubble. One study demonstrated soil loss was dramatically reduced from 50 tonnes/hectare/year down to 6t/ha/year if stubble was mulched, and 1t/ha/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 very few herbicides. Roundup® (360 grams/litre active ingredient) entered the market in 1974 but cost $20/litre, and at that time growers were using 1-2L/ha," he said.
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, were initiated in Queensland in the mid-1970s.
Then in 1968 a study, started at Warwick in southeast Queensland provided more support for conservation farming methods. It clearly showed that where there was less tillage or no tillage and stubble retained, an extra 30-50mm 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 explained.
"Then there was an accumulation of foliar and root diseases which got in the way of maximising the improved water capture."
The finding triggered additional trial work and from 1968-90 researchers focused on breeding of root lesion nematode-resistant varieties. In response to the issue of root diseases, the NSW Department of Agriculture decided to trial no tillage in tandem with the rotation of other crops like 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 in machinery followed suit.
So, should growers fear the return of cultivation nowadays?
"The occasional working of a no tillage paddock may 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 go to https://grdc.com.au/podcasts.
A GRDC Update paper on this topic is available at https://bit.ly/2CM2RnK.
