Zero till versus plough
FIFTY years ago, the pioneers of zero and minimum tillage cropping systems had a challenging time convincing researchers and growers 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 podcast series was Associate Professor David Freebairn from the Centre for Engineering in Agriculture at the University of Southern Queensland.
Professor Freebairn is wellknown in 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 shared 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 industry stakeholders informed.
Professor 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 run-off and erosion.
Professor Freebairn has now reviewed the past 50 years of research into zero and minimum till practices. Since the 1960s there have been two 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 run-off showed quite early the dramatic impacts of retaining stubble. One study showed soil loss was dramatically reduced from 50 tonnes per hectare per year down to six tonnes if stubble was mulched and one tonne if zero tillage was implemented.
Professor 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 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, 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,” Professor Freebairn said.
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,” he said.
■ Listen to the podcast at grdc.com.au/podcasts.
INNOVATION: The pioneers of zero and minimum tillage cropping systems had a challenging time convincing growers these systems had benefits. INSET: Professor David Freebairn.