Yield boosts possible in deep sand

Funded by GRDC, the study has been led by the Australian Controlled Traffic Association with research inputs from various organisations, with SARDI's Nigel Wilhelm leading the project.

"At the start of the trial, in some of the medium to high rainfall zones of Australia, up to 30pc of farmers were using CT methods, but at the time, adoption in low rainfall areas was around 3pc, so that was the reason for doing this project," Mr Wilhelm said.

"Based on the results we've seen in medium rainfall zones, the benefits of removing heavy vehicles from cropped areas of the paddock and hence reducing soil compaction were quite dramatic, and farmers have seen substantial increases in crop production by doing that."

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Trial sites at Lake Cargelligo, NSW, Swan Hill, Vic, Minnipa and Loxton, were a major component of the study.

Heavy trafficking onto a wet soil was imposed onto plots at the start of each trial, with the yields compared to plots with no trafficking.

Crop performance was then monitored in four consecutive years, with crop rotations including wheat, barley, field peas and vetch.

The most encouraging results were from Loxton, where data suggested CT was likely to improve yields from 15pc to 20pc.

Mr Wilhelm said sandy soils would be particularly responsive to CT when the process was coupled with deep ripping.

"If you add the benefits of deep ripping - and CT allows you to navigate a paddock that you've deep ripped, without getting bogged in sand, or without compacting sand you've just put lots of time and effort into uncompacting - then CT makes a lot of sense on sands," he said.

"If you deep ripped sandy areas of paddocks, then managed those paddocks with a full CT system, you could expect a 0.5 tonne a hectare to 1t/ha increase in production from the deep ripping in the first two seasons, which you could prolong, because you're not driving back over (the deep ripped soil)," he said.

Mr Wilhelm said the best approach to taking on CT was to be patient.

"You could buy a whole new set of gear, and move to a completely new CT system within a few weeks, but that would be very expensive," he said.

"If you're patient and adjust machinery as you go through a normal machinery replacement schedule, you can get into CT at much less cost and the whole process will be far more economically viable."

SARDI researcher Nigel Wilhelm, who has led a five year study into potential benefits of adopting controlled trafficking systems in low rainfall zones, said there were tools available to help farmers make decisions about CT.

One of these is the CTF Calculator, a tool developed in WA that provides information and estimates regarding CT farming methods.

"It calculates what your current trafficking area is, and what it could become if you change your gear, it's quite a useful tool for investigating CT," Mr Wilhelm said.

"Farmers can input their own machinery specifications, and the app will calculate how much of the paddock the farmer is driving over."

Mr Wilhelm said farmers often underestimated the amount of paddock they were covering, by as much as 50 per cent.

He said the app gave farmers realistic figures about what level of trafficking and compaction they could move to with a CT approach.

"There are figures out there that people could get down to 10-12pc of the paddock trafficked, but realistically, that figure is probably more in the 15-20pc range, and this app gives farmers that realistic expectation."

He said it was important to consider soil type and consult with others who had already switched to CT, when considering adoption of the method.

"If you want to put hay in the paddock, that's difficult with CT. If a crop lodges or bends over, and you're on CT, you have circumstances where you have to move, that may undermine some of the benefits of CT," he said.