DECLINING soil carbon and rising disease pressure in crops is an Australia-wide challenge and yet tools to manage it are already at hand.
When crops no longer perform as they once did revert soil to pasture and graze it for a few years. Bring it back into crop production and the results will amaze you.
So say Lindsay Bell, farming systems scientist with CSIRO Toowoomba, and Mal Ryley, plant pathologist in summer field crops for 32 years with QDAF Toowoomba, who gave an inspiring presentation at Lismore to agronomists from the Richmond and Clarence Valleys earlier this week.
Cropping and pasture exist side by side on the North Coast but the good oil from Toowoomba suggests swapping sides of the fence every few years to boost soil carbon and increase beneficial microbes which feast on disease.
Having suggested that Dr Bell and Dr Ryley both admit that zero data, in the rigorous scientific sense, exists on far north coast cropping rotations.
However, there is every evidence to suggest that such a rotation, which involves a farm looking after livestock as well as monoculture plants, is particularly good for soil, leading to stronger farm resilience as a direct result of increased microbe activity underground.
Carbon content ramps up quickly under pasture with so many vigorous roots providing support for microbes, and leaving drainage pathways when they decompose. Increased micobial activity competes well against disease like charcoal rot, especially prevalent in coast soybean crops as late summer approaches.
“We have seen dramatic decline crown rot and yellow leaf spot disease in soil under pasture as well,” said Dr Bell. “Interestingly Fusarium sometimes increases under pasture.”
Increased microbial competition, encouraging the creation of ‘good nematodes’ also reduced the population of crop damaging root lesion nematode.
Beneficial mycorrhiza fungi was also more prevalent under pasture than in cropping soils.
When creating pasture Mr Bell advised farmers not skimp on seed when transitioning from cropping, to minimise loss of production during that first year.
“Get your agronomy right,” he said. “Plant pasture as if it was a crop.”
Choosing the right grass might also make the transition back to cropping a lot easier, they said, citing Panic as an option with easy-to-establish Rhodes hard to destroy. Whatever the variety it was important to let bare soil dry out before planting a new crop. Grazing livestock will return better than cutting and carting hay.
