Zero till key to future cropping

The adoption of zero till farming systems will be vital to fully capitalise on cropping opportunities in high rainfall zones across Australia and overseas.

Farmers around the globe have traditionally ploughed soils prior to seeding and to control weeds.

Minimum tillage systems are now common in Australia, but there is increasing evidence to suggest the absence of tillage — or zero till — is more effective to produce superior crops with less weed pressure.

South Australian grain producer Stephen Ball, of Riverton, recently completed a Nuffield Australia Farming Scholarship, funded by the Grains Research and Development Corporation (GRDC), investigating the application of zero tillage farming techniques in Australia’s high rainfall zones.

He spent most of 2010 travelling to three continents to interview scientists, agricultural researchers and farmers and found no scientific foundation for the traditional convention of tilling the soil.

He said there was mounting evidence that adopting zero till farming practices could significantly boost productivity for Australian grain growers.

“The components of zero till, when used as a system, have benefits ranging from water use efficiencies and nutrient availability to creating a well-functioning soil biota, ” he said.

“Over time, the farmer can achieve increased yields and less use of inputs, such as fertiliser and chemicals.

“The right machinery, set up correctly, can also reduce seeding rates due to higher germination percentages and lower fuel consumption.”

Mr Ball said high rainfall zones in Australia’s grain farming regions typically received 500–650mm of rainfall annually, rainfall was one third greater than evaporation and the growing season was longer than nine months.

These areas were targets for potential expansion of grain production.

Mr Ball said in the next 30 to 50 years, climate change could mean current high rainfall zones could become the most reliable farming regions in the country and there was likely to be a shift out of grazing and pasture into cropping in these areas.

His report, published by Nuffield Australia earlier this year, argued that zero till farming would be vital to fully capitalising on these cropping opportunities.

Mr Ball said the components of zero till delivered healthier soils through absence of tillage, balanced and diverse rotations and soil cover.

To achieve zero soil tillage, farmers could use direct sowing with a disc seeder, broadcasting of crop seeds or direct placing of planting material into the soil. The aim should be no or minimal disturbance.

Mr Ball said biodiversity could be achieved by sound crop rotations and he recommended including grasses and broadleaf crops for cool and warm seasons if possible.

He said maintaining cover over the soil was central to improving soil biodiversity and overall crop health.

“Aim to retain all of your stubble and residue to keep 100 per cent soil cover, ” he said.

“You are giving this back to feed the soil organisms, known as biota.

“To improve soil fertility under zero till, it is imperative to increase organic matter by retention of all biomass. That is the residue left on the surface, combined with root structures decaying in the soil.”

Mr Ball said macro and micro organisms in the soil biota helped improve soil structure and delivered better nutrient cycling of nitrogen, phosphorous and sulphur.

He said this promoted better water use efficiency by better water penetration and retention.

Managing stubble loads continued to be a challenge for farmers in high rainfall zones and some had reservations about the effectiveness of disc seeders. Older machinery models had struggled in wet and sticky soils that often accumulated around the moving parts of the disc or clogged the seed boot outlets.

He said many farmers had experienced problems associated with hard solid, disc machines with insufficient down pressure and not enough resistance for cutting residue.

But Mr Ball said new double or triple disc units could handle more than 10 tonnes per hectare of stubble.

He said the ideal unit featured a double offset disc of two differing sizes, a small seed firmer wheel, a depth wheel or gauge independent of any furrow closer, a depth wheel that held the soil in place as the blade pulled from the soil and a close furrow.

“Another benefit of disc machines over the tined openers is that they have consistent seed placement, as discs tend to have exacting depth gauge wheels, ” he said.

Mr Ball said disc seeders improved timeliness of sowing, as they were able to obtain good results at speeds of up to 15km/hour. This meant more crop could be sown each day.

“This gets the crop into the ground at the optimum seeding date, which adds to increased grain yield at the end of the season, ” he said.

“Other studies have shown a decrease in fuel consumption of 66 per cent compared with conventional tillage and a 15 per cent reduction compared to use of knife points and no-till.”

Mr Ball warned the benefits of implementing zero till changes often took years and there could be some yield losses in the transition period.

To overcome grower resistance to zero till systems, he urged the industry to implement long term trial sites to demonstrate and quantify the improvements on offer under high rainfall zone conditions in Australia to help convince farmers of their merit.