Dishing the dirt
There’s a new crop that has increasing numbers of Australian farmers excited, but it has nothing to do with wool, wheat or beef. You can’t see it, you can’t eat it and you can’t win prizes with it at the local agricultural show. But farmers are hoping it will not only heal their struggling soils but make them players in the new global carbon economy. For much of the past decade, large areas of Australia have been in the grip of drought. Some argue that it’s just another dry spell in a country with a reputation for droughts and flooding rains, but the majority now agree that drier times are here to stay. For example, rainfall has plummeted in the Murray-Darling river basin, a vast area where more than a fifth of Australia’s food is grown. Indeed, by 2030, the predictions are that the Murray-Darling area will receive 41 per cent less rainfall as a result of climate change. While these forecasts have some farmers throwing their hands up in defeat, others believe they could continue doing business into a drier future, using a strategy called ‘carbon farming’. This simply means using the plants you grow on your farm to ‘harvest’ carbon from the atmosphere and return it to the soil.
Dr Brian Murphy, a senior soil scientist with the New South Wales Department of Environment and Climate Change, explains: ‘First, the leaves of the plant absorb carbon dioxide, which finds its way to the growing root system. The roots exude chemicals (containing carbon molecules) into the soil, which attract fungi. The fungi grow on the roots and assimilate the carbon, and eventually, as the roots slough off and break down, the carbon becomes incorporated into the soil.’
The potential for sequestering carbon in soils, some researchers say, is huge, and Alex McBratney, professor of soil science at the University of Sydney, has calculated just how much. If the carbon content of a quarter of the world’s soils was increased by just one per cent (by changing agricultural practices), he says, it would result in the removal of 300 gigatonnes of CO2 from the atmosphere. This is roughly 330 times more than all of the greenhouse gases emitted by the UK in 2003. While not all soils have the capacity to sequester much more carbon (for example, sandy soils and those in very dry areas), supporters of soil carbon sequestration say we’ve barely scratched the surface.
But while farmers are happy that they can help remove carbon from the atmosphere, they are even more interested in the fact that a high carbon content can buffer a soil against climate change. ‘Soils can respond to extreme events better if the carbon content is high,’ says Dr Jeffrey Baldock, a research leader with the land and water division of Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). If the soil contains plenty of carbon, he says, it will be able to retain more water, cope better with temperature extremes and retain more nutrients.
Australian soils now contain only about half the carbon they did before European settlement. Ploughing, burning stubble and removing crop waste gradually strips the carbon from the soil, leaving it without structure and unable to hold much water.
Murphy says improving agricultural practices can increase the amount of carbon being ‘fixed’ in the soil. The soil under an intensively farmed wheat crop (cultivated six times a year and the stubble burnt after the harvest) will contain about 20–23 tonnes of carbon per hectare, but soil under the same crop grown using no cultivation and no burning may have as much as 30 tonnes of carbon per hectare. That’s close to a 50 per cent increase in carbon capture.
The idealist
David Marsh started out as a regular farmer, but had an epiphany about ten years ago when he realised the effect that his activities were having on the environment. Today, he’s an advocate of the ‘planned grazing’ method on his 800-hectare property in the Boorowa district, four hours’ drive southwest of Sydney. Ask him about how he farms to reduce his ecological impact and he’ll talk passionately for hours.
After he and his family purchased their property, Allendale, in the 1960s, they started out like conventional farmers, growing wool and planting crops. ‘But when we added it up, cropping wasn’t making sense environmentally or financially. We were always questioning what we did and looking around for different ways of doing things.’
Marsh became interested in Holistic Management, a system developed by Allan Savory, a Zimbabwean biologist who was trying to solve the problem of desertification. ‘He noticed that no matter whether a far-mer lived in a rich or a poor country, land deg-radation was always there,’ Marsh says. So what was the common factor? ‘It was that, rich or poor, we all make decisions in a linear fashion towards economic goals and objectives. When we do that, we generally ignore or defer the costs to ecosystems and ignore the social effects.’
Marsh’s 700 cattle are allowed to graze each of his roughly ten-hectare paddocks for no longer than ten days each year, giving the grass a better chance of recuperating. ‘When you defoliate a perennial plant and it begins to grow again, that’s when you should stop grazing it. When you graze a plant, you should always give it an adequate time to recover; otherwise you weaken it for the next season.’ The end result on his farm is a landscape – and plant community – that progresses to a more complex and resilient state.
How does this relate to increasing soil carbon? Marsh says his pasture has at least ten times the volume of roots of other properties in the area. These roots sequester carbon, pulling it from the atmosphere and keeping it in the soil. Measurements of soil carbon on his property seem to be verifying this.
The pragmatist
Rowan Ford’s 4,000-hectare grazing property in Western Australia is a 30-kilometre drive from the nearest ‘town’, Binnu, which has a population of just eight, including the dog. Known as ‘yellow sandplain country’, this land gets just 300 millimetres of rain in a good year, about half that of London. In a bad year, of which there have been many since 2000, you may get just 60–100 millimetres of rain spread out over the whole year. Yet even in a landscape as harsh as this, the soil is being managed in order to increase carbon levels.
A few years back, Ford switched to growing perennials – long-lived plants that produce extremely deep roots – for grazing his cattle. ‘When cattle graze the shoots, the root system dies back to the same level, leaving the carbon behind in the soil,’ he says. ‘Then the plants regrow more roots, then you graze them again and the roots die back again, sequestering more carbon.’
His property is one of a dozen involved in a three-year trial being carried out by the state’s Northern Agricultural Catchments Council. A voluntary agreement has been drawn up with mining company Rio Tinto, which will buy any ‘carbon credits’ from the farmers (in the form of carbon sequestered in the soil) to offset its own emissions. ‘My idea with soil carbon sequestration is even if you only cover your own carbon emissions, it’s a good idea because [once a carbon emissions trading scheme comes in] they are going to charge us like a wounded bull,’ says Ford.
The activist
Some farmers are adamant that they should get a financial return for sequestering carbon in their soils. New South Wales farmer Michael Kiely is a member of the Carbon Coalition, which is pushing hard for the creation of such a scheme. ‘Soil biomass is a natural carbon sink and should be used to create carbon credits that can be traded alongside those currently traded for forests,’ he says. (Under Australia’s current Kyoto target for the agricultural sector, only growing forests is recognised as a valid method for sequestering carbon.) He points to US farmers, who have, in the past, been paid to leave certain areas ungrazed in order to sequester more carbon.
However, as CSIRO’s Jeffrey Baldock told a carbon forum in Geelong in August, when these subsidies are removed, the land is put back into production and carbon is again lost from the soil.
Kiely and other farmers are also concerned that farmers will soon be charged for the greenhouse gases they produce. Indeed, about 16 per cent of Australia’s greenhouse gas emissions come from the agricultural sector, mainly from livestock belching methane, fertilisers releasing nitrous oxide and the use of fuels. At this stage, the Australian federal government is proposing to charge the agricultural sector for its emissions from 2015, after it introduces a carbon emissions trading scheme. But it hasn’t yet decided whether farmers will also have the chance to offset their carbon liability through soil carbon sequestration. This is partly because many uncertainties remain as to the extent to which some Australian soils are able to capture and retain carbon for long periods. There are also major concerns that the whole plan will be too difficult and expensive to audit and make accountable.
One of the main concerns scientists have about the viability of soil carbon farming is that Australia doesn’t have the rainfall to grow enough biomass to sequester significant amounts of carbon. But Kiely says that while the scientists mean well, they overlook the biological dimensions of the process. ‘There’s an unimaginable “Star Wars” going on out there in the soil. One hectare can contain 50 tonnes of living microorganisms [that are sequestering carbon]. ‘Some of the scientists only study the losses of carbon, and so they always say how bad things are. But they don’t measure the gains – it isn’t part of the brief.’
If climate change continues to wreak havoc on Australia’s breadbasket, soil carbon sequestration, despite its difficulties, may be the only way for agriculture to survive.
Sugar gives carbon a caning
Sugarcane has had a bad reputation with environmentalists for years, but now researchers in Australia say that it offers a cunning way to sequester the maximum amount of soil carbon possible.
Jeff Parr and Leigh Sullivan of Southern Cross University have been studying plantstones – also called phytoliths – microscopic balls of silica naturally made by plants as a defence mechanism against insects and dry periods. Phytoliths incorporate carbon as they form, and once the plant breaks down, they are virtually indestructible, remaining in the soil for thousands of years. This is exactly what soil carbon farmers are looking for: a way to store carbon in the soil that is stable over long periods of time, says Parr.
The researchers have found that the amount of carbon stored in phytoliths varies dramatically from one variety of sugarcane – or wheat, barley or any other type of grass – to the next. The best so far is a cultivar of sugarcane that can lock up 0.66 tonnes of CO2 equivalents per hectare per year. The researchers are now developing a database of phytoliths so farmers can choose to grow those varieties that sequester the maximum amount of carbon in their soils. ‘So far we have found no trade-off between yield and carbon sequestration,’ the researchers say.
January 2009
Dr Brian Murphy, a senior soil scientist with the New South Wales Department of Environment and Climate Change, explains: ‘First, the leaves of the plant absorb carbon dioxide, which finds its way to the growing root system. The roots exude chemicals (containing carbon molecules) into the soil, which attract fungi. The fungi grow on the roots and assimilate the carbon, and eventually, as the roots slough off and break down, the carbon becomes incorporated into the soil.’
The potential for sequestering carbon in soils, some researchers say, is huge, and Alex McBratney, professor of soil science at the University of Sydney, has calculated just how much. If the carbon content of a quarter of the world’s soils was increased by just one per cent (by changing agricultural practices), he says, it would result in the removal of 300 gigatonnes of CO2 from the atmosphere. This is roughly 330 times more than all of the greenhouse gases emitted by the UK in 2003. While not all soils have the capacity to sequester much more carbon (for example, sandy soils and those in very dry areas), supporters of soil carbon sequestration say we’ve barely scratched the surface.
But while farmers are happy that they can help remove carbon from the atmosphere, they are even more interested in the fact that a high carbon content can buffer a soil against climate change. ‘Soils can respond to extreme events better if the carbon content is high,’ says Dr Jeffrey Baldock, a research leader with the land and water division of Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). If the soil contains plenty of carbon, he says, it will be able to retain more water, cope better with temperature extremes and retain more nutrients.
Australian soils now contain only about half the carbon they did before European settlement. Ploughing, burning stubble and removing crop waste gradually strips the carbon from the soil, leaving it without structure and unable to hold much water.
Murphy says improving agricultural practices can increase the amount of carbon being ‘fixed’ in the soil. The soil under an intensively farmed wheat crop (cultivated six times a year and the stubble burnt after the harvest) will contain about 20–23 tonnes of carbon per hectare, but soil under the same crop grown using no cultivation and no burning may have as much as 30 tonnes of carbon per hectare. That’s close to a 50 per cent increase in carbon capture.
Start the slideshow (12 pictures)
The idealist
David Marsh started out as a regular farmer, but had an epiphany about ten years ago when he realised the effect that his activities were having on the environment. Today, he’s an advocate of the ‘planned grazing’ method on his 800-hectare property in the Boorowa district, four hours’ drive southwest of Sydney. Ask him about how he farms to reduce his ecological impact and he’ll talk passionately for hours.
After he and his family purchased their property, Allendale, in the 1960s, they started out like conventional farmers, growing wool and planting crops. ‘But when we added it up, cropping wasn’t making sense environmentally or financially. We were always questioning what we did and looking around for different ways of doing things.’
Marsh became interested in Holistic Management, a system developed by Allan Savory, a Zimbabwean biologist who was trying to solve the problem of desertification. ‘He noticed that no matter whether a far-mer lived in a rich or a poor country, land deg-radation was always there,’ Marsh says. So what was the common factor? ‘It was that, rich or poor, we all make decisions in a linear fashion towards economic goals and objectives. When we do that, we generally ignore or defer the costs to ecosystems and ignore the social effects.’
Marsh’s 700 cattle are allowed to graze each of his roughly ten-hectare paddocks for no longer than ten days each year, giving the grass a better chance of recuperating. ‘When you defoliate a perennial plant and it begins to grow again, that’s when you should stop grazing it. When you graze a plant, you should always give it an adequate time to recover; otherwise you weaken it for the next season.’ The end result on his farm is a landscape – and plant community – that progresses to a more complex and resilient state.
How does this relate to increasing soil carbon? Marsh says his pasture has at least ten times the volume of roots of other properties in the area. These roots sequester carbon, pulling it from the atmosphere and keeping it in the soil. Measurements of soil carbon on his property seem to be verifying this.
The pragmatist
Rowan Ford’s 4,000-hectare grazing property in Western Australia is a 30-kilometre drive from the nearest ‘town’, Binnu, which has a population of just eight, including the dog. Known as ‘yellow sandplain country’, this land gets just 300 millimetres of rain in a good year, about half that of London. In a bad year, of which there have been many since 2000, you may get just 60–100 millimetres of rain spread out over the whole year. Yet even in a landscape as harsh as this, the soil is being managed in order to increase carbon levels.
A few years back, Ford switched to growing perennials – long-lived plants that produce extremely deep roots – for grazing his cattle. ‘When cattle graze the shoots, the root system dies back to the same level, leaving the carbon behind in the soil,’ he says. ‘Then the plants regrow more roots, then you graze them again and the roots die back again, sequestering more carbon.’
His property is one of a dozen involved in a three-year trial being carried out by the state’s Northern Agricultural Catchments Council. A voluntary agreement has been drawn up with mining company Rio Tinto, which will buy any ‘carbon credits’ from the farmers (in the form of carbon sequestered in the soil) to offset its own emissions. ‘My idea with soil carbon sequestration is even if you only cover your own carbon emissions, it’s a good idea because [once a carbon emissions trading scheme comes in] they are going to charge us like a wounded bull,’ says Ford.
The activist
Some farmers are adamant that they should get a financial return for sequestering carbon in their soils. New South Wales farmer Michael Kiely is a member of the Carbon Coalition, which is pushing hard for the creation of such a scheme. ‘Soil biomass is a natural carbon sink and should be used to create carbon credits that can be traded alongside those currently traded for forests,’ he says. (Under Australia’s current Kyoto target for the agricultural sector, only growing forests is recognised as a valid method for sequestering carbon.) He points to US farmers, who have, in the past, been paid to leave certain areas ungrazed in order to sequester more carbon.
However, as CSIRO’s Jeffrey Baldock told a carbon forum in Geelong in August, when these subsidies are removed, the land is put back into production and carbon is again lost from the soil.
Kiely and other farmers are also concerned that farmers will soon be charged for the greenhouse gases they produce. Indeed, about 16 per cent of Australia’s greenhouse gas emissions come from the agricultural sector, mainly from livestock belching methane, fertilisers releasing nitrous oxide and the use of fuels. At this stage, the Australian federal government is proposing to charge the agricultural sector for its emissions from 2015, after it introduces a carbon emissions trading scheme. But it hasn’t yet decided whether farmers will also have the chance to offset their carbon liability through soil carbon sequestration. This is partly because many uncertainties remain as to the extent to which some Australian soils are able to capture and retain carbon for long periods. There are also major concerns that the whole plan will be too difficult and expensive to audit and make accountable.
One of the main concerns scientists have about the viability of soil carbon farming is that Australia doesn’t have the rainfall to grow enough biomass to sequester significant amounts of carbon. But Kiely says that while the scientists mean well, they overlook the biological dimensions of the process. ‘There’s an unimaginable “Star Wars” going on out there in the soil. One hectare can contain 50 tonnes of living microorganisms [that are sequestering carbon]. ‘Some of the scientists only study the losses of carbon, and so they always say how bad things are. But they don’t measure the gains – it isn’t part of the brief.’
If climate change continues to wreak havoc on Australia’s breadbasket, soil carbon sequestration, despite its difficulties, may be the only way for agriculture to survive.
Sugar gives carbon a caning
Sugarcane has had a bad reputation with environmentalists for years, but now researchers in Australia say that it offers a cunning way to sequester the maximum amount of soil carbon possible.
Jeff Parr and Leigh Sullivan of Southern Cross University have been studying plantstones – also called phytoliths – microscopic balls of silica naturally made by plants as a defence mechanism against insects and dry periods. Phytoliths incorporate carbon as they form, and once the plant breaks down, they are virtually indestructible, remaining in the soil for thousands of years. This is exactly what soil carbon farmers are looking for: a way to store carbon in the soil that is stable over long periods of time, says Parr.
The researchers have found that the amount of carbon stored in phytoliths varies dramatically from one variety of sugarcane – or wheat, barley or any other type of grass – to the next. The best so far is a cultivar of sugarcane that can lock up 0.66 tonnes of CO2 equivalents per hectare per year. The researchers are now developing a database of phytoliths so farmers can choose to grow those varieties that sequester the maximum amount of carbon in their soils. ‘So far we have found no trade-off between yield and carbon sequestration,’ the researchers say.
January 2009
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