WithTheGrain: Yield gains to be made in controlling traffic

Author: | Date: 12 Jul 2018

The impact of heavy vehicle movements compacting soils and any possible effects on crop yields is under investigation in the low-rainfall zone (LRZ) of the GRDC’s southern region as part of controlled-traffic farming (CTF) research.

Four sites with varying sand and clay characteristics typical of the LRZ feature in the GRDC investment which is now entering the final year of work as researchers evaluate the benefits of CTF in non-traditional areas.

South Australian Research and Development Institute (SARDI*) farming systems leader –Dr Nigel Wilhelm says the new focus on measuring heavy vehicle compaction has become even more important as applying inputs in-season is now common even in this low production zone.

“Twenty years ago that rarely happened as LRZ farmers would’ve sown the paddock and then shut the gate until harvest,” he says.

“Now farmers in all zones are putting out in-season inputs when they never used to, so several passes in the growing season is not unusual.

“There is the potential that if farmers continue using a conventional system without strategic traffic planning and they start running over the same passes when the soil is wet the crop production in those tracks will be affected.

“On top of that when you sow it next year you may well have some significant yield losses because that soil has been crushed several times while wet the previous year.”

Deep ripping forms a part of the controlled-traffic farming (CTF) trials across two sites in South Australia and two in Victoria, including the pictured Koolonong, Victoria site.
Deep ripping forms a part of the controlled-traffic farming (CTF) trials across two sites in South Australia and two in Victoria, including the pictured Koolonong, Victoria site.

Interim results from three trafficking treatments of one pass in dry conditions, one pass in moist conditions and three passes in moist conditions are proving substantial for the wet conditions only.

The three passes in moist conditions caused yield losses of 5-40 per cent across most sites, the single pass in moist conditions trials occasional yield losses of between 5-10 per cent, and the one pass in dry conditions test resulted in losses rarely.

“In terms of context we’re talking up to 50 per cent yield losses for the track itself and while over the whole paddock it’s a much smaller figure, it can equate to a 3-5 per cent production loss across the whole paddock as a worst case scenario,” Dr Wilhelm says.

“This is a real possibility in many operations when you consider two passes with a boom spray could realistically occur while a paddock is in crop.

“This is a benefit for LRZ farmers who move to a CTF system, but it is important to keep CTF in context where farmers using auto steer are already in a semi-CTF system.

“A farmer who isn’t matching his machinery width, but is using auto steer is probably only trafficking 40-50 percent of his paddock now and if he moves to a full CTF system it’s still likely to be 15-20 percent.”

South Australian Research and Development Institute (SARDI*) farming systems leader –Dr Nigel Wilhelm presents the current results of the research trial site at Minnipa for at the local field day.
South Australian Research and Development Institute (SARDI*) farming systems leader –Dr Nigel Wilhelm presents the current results of the research trial site at Minnipa for at the local field day.

Dr Wilhelm says a gradual change to CTF in the LRZ does not have to be a major investment if routine updating of machinery incorporates changes to CTF such as common swath and axle widths. This could assist farmers in chasing down the potential production losses without creating large extra expenses.

Interestingly, the compaction trials on the calcareous soils of the Eyre Peninsula have shown the three passes in moist conditions to have little to no effect on crop production.

“That particular environment and potentially anywhere with a very calcareous soil type seems to carry heavy vehicles quite well,” Dr Wilhelm says.

“The logistical benefits of making a changeover to CTF are still there but somebody contemplating that move needs to do so knowing that crop production might not change or be much smaller in that environment.”

Adoption of CTF in the LRZ of south-eastern Australia is below 10 per cent of grain growers compared to nearly 40 per cent in several other Australian regions.

A weather station at the Loxton trial site measures local conditions including rainfall and wind speed.
A weather station at the Loxton trial site measures local conditions including rainfall and wind speed.

Dr Wilhelm says for some growers, CTF in the LRZ raises concerns of wind erosion issues where this isn’t a consideration in the traditional CTF practicing areas of Australia.

“A feature of CTF is you are driving over laneways repeatedly and on sandy soils that’s not always a good thing because wind erosion is something that a lot of farmers are very nervous about,” he says.

“We would recommend that farmers with sandy soils and moving to CTF should still sow their wheel tracks.

“The more typical CTF system is to have an unseeded wheel track, but growers are encouraged to consider sowing those wheel tracks for paddocks prone to wind erosion as this would give them more protection.”

Dr Wilhelm says a LRZ CTF adaption to reduce wind erosion risk could be to reset laneways every 5-10 years. He says this isn’t a traditional approach but this would be strategy to address the unique needs of the LRZ environments.

Work is also starting this year to investigate the benefits of deep ripping in a CTF operation. Dr Wilhelm says sands settle within a few years after ripping but this research will investigate how long the treatment could last if minimal heavy vehicle movement occurs in the ripped portions of the paddock.

*SARDI is a division of Primary Industries and Regions SA

GRDC Research Code: ACT00004

More information

Nigel Wilhelm, 0407 185 501, nigel.wilhelm@sa.gov.au

Useful resources

GRDC Fact Sheet – Controlled traffic farming

GRDC Project code: ACT00004