Nuffield Australia 2017 Scholar
Multi-species cover crops: unearthing the secrets to improved soil health
Multi-species cover cropping is the most effective way to improve soil health, and has the potential to reverse damage caused by years of conventional, full tillage farming practices and boost the sustainability of broadacre dryland cropping in Australia. A report released by 2017 Scholar, Alex Nixon, collates global research on sustainable farm management practices and reveals that by using cover crops, farmers can greatly increase the health of their soils. Supported by the Grains Research and Development Corporation (GRDC), Mr Nixon used his Nuffield Scholarship to research the use of cover crops around the world and develop a blueprint for the adoption of the emerging land management practice back home.
Mr Nixon runs an 8,500-hectare cattle and cropping operation near Roma, Queensland. As the third generation of his family to farm the land, and with a young family of his own, a desire to leave his property in better condition for future generations motivated his research.
“Successful, sustainable farming businesses depend on the health of their soils. Sown after completion of a cash crop, a multi-species cover crop can greatly enhance soil health by boosting biodiversity, ground cover and soil organic matter,” Mr Nixon said.
Researching cover crop trials in the United States, Mr Nixon revealed the benefits that cover cropping can have on the amount of organic matter present in soil.
“Field trials conducted in North Carolina and North Dakota revealed that several consecutive years of cover cropping had allowed organic matter to build up from 1.2 per cent to 6.7 per cent. The residue from the cover crops slowly breaks down, providing food for microbes and boosting moisture retention, acting like a mulch.”
Acknowledging that cover cropping in the Australian broadacre sector to date has been largely based on single species crops, the report reveals that multi-species crops are more beneficial because they avoid the presence of a monoculture and boost microbial diversity and activity.
“Single-species cover crops do enhance ground cover, but by adding even one or two different species into a cover crop the microbial activity can be greatly enhanced, boosting the diversity of the soil ecosystem,” he said.
Mr Nixon’s research goes beyond the raw benefits of multi-species cover cropping, to explore the viability of the practice in an Australian context.
“Despite the benefits, a number of barriers to adoption remain for Australian farmers,” he said.
“Upfront costs can be an issue. Cover crop seed is very expensive, as is the investment required for machinery or contract sowing. Visiting farms in the United States and England, it was clear that the initial cover cropping season can result in some financial deficits. At Overbury Farms in England, long-term soil conservation had been prioritised over the short-term bank balance, and lower income was being supplemented by other revenue streams.”
Mr Nixon’s report recommends that Australian growers looking to implement a multi-species cover crop regime start small, and consider the frequency and size of cover rotations based on the benefits they can produce.
“While implementing diverse cover-crops can pose initial economic issues, the long-term environmental and economic benefits outweigh any initial costs. As soil health improves, input costs on fertiliser and chemicals decrease, while cash crop yields increase. A cover crop also opens up opportunity for alternative revenue streams through livestock grazing or agistment, before the cash crop goes back in. Through careful management, multi-species cover cropping is a viable option for Australian broadacre farmers seeking to improve soil health and preserve the landscape for generations to come.”