Southern farmer Colin Harper has drastically slashed his fertiliser costs by recycling tractor exhaust fumes into his cropping soils.
While exhaust fumes are rarely considered a benefit to human health, Mr Harper’s Ariah Park crops are proof that pumping emissions into the seedbed at sowing actually delivers environmental benefits to the soil profile – and helps farm productivity.
Soil biology is stimulated with improved carbon rates as well as other useful elements including calcium, nitrogen, phosphorous, iron and zinc.
As the soil biology improves, promoting crop organic matter and root development, a cycle of better soil nutrition has gradually reduced Mr Harper’s need for extra fertiliser inputs on his 2230-hectare property “Taravale” thanks to fresh microflora feeding the plants and more decaying plant material feeding the soil.
“We’re getting about 10 to 15 per cent better seedling germination, improved worm numbers and better soil moisture holding capability,” he said.
“We had no spring rain at all last year, but our grain weight and quality was probably the best I’ve ever grown, yet our neighbours all reported a lot of pinched grain problems.”
Mr Harper conceded it was “a bit odd to think diesel fumes are not toxic” given the danger they represented to human health, but he noted fuel was derived from oil, which itself is was once just living organic matter and water.
Biological Farmers of Australia (BFA) agrees, approving use of his exhaust fertilising process for BFA’s organic registered croppers.
The relatively simple and compact exhaust cooling system, is mounted flat on the roof of his 260 kilowatt John Deere tractor cab.
Hot fumes are funnelled direct from the exhaust stack to the big radiator-styled unit which is fitted with five electric fans controlled by thematic switches to reduce the emissions temperature from about 300 degrees C to 80C in less than half a second.
The fumes are then pumped via a flexible hose to the sealed air seeder unit behind, coating seed in warm, moist air as it blows into the soil bed.
Mr Harper is convinced the seed coating process contributes to better germination, while the soil benefits from the rest of the gas.
“It makes much much more sense than losing it into the atmosphere.”
He and Temora aviation museum jet aircraft engineer David Finch initially devised their cooling and soil injection system over several years to win a regional runner up award in The Land’s Farm Inventor competition in 2012.
Commercial versions have since been sold for about $30,000 to croppers from Moree to Trundle and even to a US buyer.
“A decent sized farming operation will probably pay for the unit in just one to two years with the savings they can make on chemical fertiliser inputs,” Mr Harper said.
He cut his typical mono-ammonium phosphate (MAP) fertiliser inputs from 100 kilograms a hectare of to 75kg in the first first year he pumped his soils with tractor exhaust, then progressively continued reducing his applications for the next two years.
The only fertiliser he pays for now is about $25/ha for liquid biological (worm juice) fertiliser to help promote extra soil microbial activity in his 800ha of cropping country.
Mr Harper said not only was his exhaust fertilised cropping rotation (canola, wheat and a two year legume-based pasture phase) paying him grain and soil quality dividends, his sheep looked healthier after grazing during the pasture stage.
“I’m very excited about the soil’s improving condition and the good results we’re getting when we return to the cropping phase for the second time,” he said.
Mr Harper said the idea of using exhaust gas as a fertiliser had been around for almost a century, but reducing the temperature quickly and making the process affordable had been typical hurdles encountered in the past.
Exhaust has also been mixed into irrigation water and used in greenhouses to stimulate plant growth.