MALLEE Sustainable Farming Systems has established a novel trial site to test the effects of recycling tractor exhaust emissions on dryland grain crops.
It is a 36.6m strip along the central length of one paddock.
"This is not a rigorous scientific project," extension officer Dr Nicole Dimos said. "It is simply a demonstration.
"We're having a look to see if the technology works."
The site includes four treatments: seed only, seed sown with exhaust in a single pass, a double pass (with exhaust applied to surface and seed planted on the second pass) or sowing by conventional practice with nitrogen fertiliser.
Soil samples were collected at sowing and four weeks post-sowing and tested for total carbon content, dissolved organic carbon and microbial biomass.
Measurements showed much variation, which Nicole said was normal, although she was unable to explain why the double pass recorded the second-lowest level of total soil carbon - 14 per cent lower than at pre-sowing - when levels increased in the single pass and control plots.
Nicole said measurements of extractable carbon, the form used by microbes, showed levels in both exhaust treatments were higher, but not significantly.
Measurement of microbial biomass, an indicator of microbial activity, showed the lowest levels in soil where nitrogen fertiliser was applied.
"The exhaust (treated soil) had high levels, but the control had the highest levels so it's hard to make claims that blowing exhaust into the soil will lead to higher microbial activity," Nicole said.
Plant counts were highly variable, but lower in the nitrogen plot because the different equipment used a seeding rate of 25kg/ha compared with 29kg/ha on the other treatments.
Nicole said a visual assessment showed no real differences between the plants by 16 weeks, although the landowners reported seeing some stripe rust in all treatments except the one that received nitrogen.
"This type of soil carbon work is not a project where we'd expect a result after one season," she said.
"It is very long-term and it is only pilot work."
Nicole said yield and grain quality would be measured after harvest and soil analysed to calculate the crop's nutrient use.
She said it was too early to endorse the system and it was up to farmers to make their own decision about whether they thought it might work.
Department of Primary Industries Mallee Research Station science leader Roy Latta said the science on the subject was "very, very, very fragile".
Lower Murray Darling CMA chairman Mark King said the Linklaters had received an incentive grant to help with the cost of machinery and similar grants were available for two other NSW landholders interested in taking part in the trial.
For more information visit Mallee Sustainable Farming or Lower Murray Darling CMA.
