Stash your carbon underground
Farmer tackles climate and boosts productivity
ROBERT Quirk is proud to have achieved 6 per cent organic soil carbon on his Tweed Valley cane property.
“I’ve been told it can’t be done, but we’ve done it,” he said.
It is a high soil carbon content for a cropping operation, achieved as part of a raft of on-property strategies employed by Robert, also the Australian Cane Farmers Association deputy chairperson, and a sustainable agriculture educator, researcher and advocate.
The property provides what Robert calls “a good living” from 100ha under cane, with 30ha to cattle.
Within sight of the sea, the Tweed River, and the Queensland border, the northern NSW property is in Mt Warning’s caldera country that has also been a historical sea bed, which presents modern-day issues with soil acidity and discharges.
“What we did here was develop the practices that allowed us to continue to farm and be very productive. The acid’s still here, but it doesn’t discharge,” he said.
Retaining organic matter in the soil has been key.
“If you have low pH, the organic matter will raise it, high pH organic matter will bring it back: it works to bring it back into equilibrium.
“Our pH has gone up by two, from three and four to five and six now. By getting that 6 per cent organic carbon level, we don’t have to use the same amount of fertiliser.
“The sugar cane gets about 90 per cent of its nutrients from the breakdown of the organic matter, and we’ve got plenty of organic matter.”
That in-soil organic matter is created by retaining residue from harvest.
“Immediately after harvest, there is about a tonne of sugar per hectare on the residue, from smashed up cane and from the extractors. So I spray it with five kilograms of urea per hectare, and that helps it turn to fungi rather than break down and go back into the atmosphere as CO2, but just stays and builds as soil carbon,” Robert said.
The increased soil organic matter has encouraged the reappearance of earthworms on site – willing volunteers that draw the surface mulch down into the soil.
His property design also includes reduced tillage, and soy rotational crops to fix nitrogen, dramatically reducing the need for additional fertiliser. If a flood event ruins that legume, lupin are planted in winter.
The improved soil health has also seen a reduction in pest insect species and disease.
“We’re not having the same trouble with pests like cane grub and pachymetra (root rot) – all the baddies – because we’re building fungi in the soil.
“The naturally occurring metarhyziums in the soil rely on other fungi to proliferate.”
With flood events in the coastal sub-tropics increasing with climate imbalances, planting on mounded rows is a strategy to reduce the capacity of flood events to destroy crops.
The presence of mulching cane matter on the ground assists with retaining soil moisture in dry periods.
A recent carbon audit on the Quirk farm shows the operation currently has sufficient offset to cover the operation for 150 years (offsetting farm vehicle use, electricity, fertiliser etc).
Given the results that are being shown in terms of carbon sequestration from these sorts of sustainable cropping operations, Robert is surprised that it isn’t figuring in establishing national renewable energy targets.
The capacity for farmers to make a difference when it comes to climate change is an issue about which Robert is passionate.
“Carbon capture in cropping like this hasn’t been considered in the targets, and I thought wow, we could really make a difference,” he said.
Robert is a member of Farmers for Climate Action, and in his presentations, he shows Australian National University research that
demonstrates that for every degree of ocean warming, the ocean rises 20cm.
“We are trying to keep warming at two degrees. It’s not going to be next year, but at some time in the next 100 to 1000 years, the warming of the great Southern Ocean, the thermal expansion, the ocean will rise 20cm for every degree.
Current sea-level rise, based on NASA data, is at 3.2mm per year, which poses some obvious and immediate risks for coastal farming operations in terms of tidal inundation events, erosion, and in the longer term, incremental but extensive permanent sea inundation over a great deal of arable coastal farming country.
Robert said a tidal anomaly had already impacted his coastal farm this year, with a low pressure system sea surge acting on a high tide.
“We had a 30cm tide anomaly. It breached our water supply weir, breached a lot of floodgates. So a 30cm sea level rise by 2050 is going to be devastating.”
Recognising these fundamental climate realities, and the desire to leave a functional planet for future generations has made Robert farm differently for 20 years.
And that sustainable switch is showing some amazing productivity figures.
“I’ve had about a
50 per cent increase in production, I’ve had a
40 per cent reduction in fertiliser application, tractor hours have gone down by 40 per cent, and labour went down by 60 per cent, so I don’t employ anybody any more, I do it all myself,” he said.
“For a period of time, the residue from a 100 tonnes-a-hectare crop, which is about average for here, you get about 15 tonnes of residue per hectare, and that’s about the equivalent of about 50kg of N, 20kg of P, and somewhere between 150 and 225kg of K.
“All your micro-nutrients are bio-available; sulphur is more available from the breakdown of residue than it is from a bag. It’s just a really good story.”
The farm is producing around 96 tonne per hectare, well above the national
❝ I’ve had about a 50 per cent increase in production, I’ve had a 40 per cent reduction in fertiliser application, tractor hours have gone down by 40 per cent, and labour went down by 60 per cent... — Robert Quirk
average of 85T per hectare.
“If you are interested in climate change, we don’t have to spend $600,000 to prove something: if we do the experiments at our own costs, and we can show that it works, then other farmers can do it, or they can not do it. But, I can tell you, it’s made me a lot of money on the farm.”
Robert travels all over the world, including Vietnam, Thailand, Nicaragua, and Fiji in just the past year alone, and regularly receives on-farm overseas visitors, to teach, pro bono, about methods of building productivity alongside sustainable growing approaches.
“Whatever we do with our farming systems into the future, we are going to have to design them to deal with wetter periods of more intense rainfall and also drier periods,” he said.
He will visit Mackay to present at the farmer-led Central Queensland Soil Health System’s Farming Carbon and our Climate field day on August 12.