No-till captures carbon for Kyoto

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Photo of Rohan Rainbow, SANTFA"s executive and scientific officer

By Emma Leonard

After spending billions of dollars exploring high-tech engineering options to sequester carbon - like pumping carbon dioxide (CO2) into underground geological structures or deep into the ocean - researchers in the US have acknowledged that farming and forestry are the most cost-effective means of removing CO2 from the atmosphere.

The process, called terrestrial carbon sequestration, reduces the amount of CO2 entering the atmosphere by physically or biologically locking up carbon. Essentially, it is the process of transforming CO2 into stored soil carbon.

Plants take up CO2 through photosynthesis and incorporate it into living plant matter. As plants die, the carbon in the leaves, stems and roots decays in the soil to become soil organic matter. Left undisturbed, soil organic matter will eventually be transformed into humus, a very stable and long-lasting form of organic matter. Left undisturbed, soils can store twice as much CO2 as the atmosphere.

With support from a GRDC travel and conference grant, Dr Rohan Rainbow of the South Australian No-Till Farmers Association (SANTFA) visited the US in 2005 to learn more about carbon sequestration and the role agriculture can play in absorbing some of the world"s CO2.

[Photo (left) by Emma Leonard: Rohan Rainbow]

The biosphere absorbs about two-thirds of all carbon emissions from human activity. However, sequestration via agriculture could absorb about 20 per cent of the world"s emissions targeted by the Kyoto agreement.

Reduced tillage or no-till are key methods for increasing sequestration, although modifying tillage systems is not the only agricultural practice that improves carbon absorption.

Photo of Rohan Rainbow and Jane Greenslade[Photo (left) by Emma Leonard: Rohan Rainbow, SANTFA"s executive and scientific officer, explains the soil compaction readings from the penotrometer to no-till farmer Jane Greenslade.]

Growing cover crops, reducing summer fallow and intensive cropping - especially with high-residue crops such as wheat, grain sorghum and corn - would all have a positive impact. Some species and varieties may be less carbon-efficient or store more carbon: deep-rooted crops, such as canola or lucerne, transfer more carbon to the subsoil.

Strategic use of fertiliser, precision agriculture or soil-specific management are all critical to soil carbon sequestration. Vegetation buffers, reducing soil erosion and converting marginal agricultural land to grassland or forest could also offer benefits.

Many of these techniques have already been shown to provide productivity benefits, but their use in carbon sequestration may also provide growers with an opportunity to become involved in carbon credit trading.

On his US trip, Dr Rainbow visited the Pacific North West Direct Seed Association, which has been one of the first conservationfarming grower groups in the world to complete a carbon credit trade. By adopting no-till for a prescribed period and area, they have struck a carbon credit trade agreement with a major US power generator.

The US, like Australia, has not signed the Kyoto Agreement, so this trade is on a voluntary, not statutory, basis.

When Dr Rainbow visited the US, the voluntary carbon market was offering less than US$2 (A$2.60) a tonne of CO2 while in Europe the figure was 19 euros (€) (A$31.40) a tonne. Globally, the benefit of reducing atmospheric CO2 concentrations is valued at more than US$25/t and carbon credits are trading on Chicago Climate Exchange for just under US$5 and €30/t.

If Australia is to become a player in the trading of carbon credits based on terrestrial carbon sequestration, Dr Rainbow says some key questions need to be answered, such as identifying how much carbon Australian soils can absorb and for how long.

Dr Rainbow says that a cooperative approach to trading offers the greatest chance of success in addressing global warming. Such an approach would involve carbon generators, potential carbon users and "storers" and governments working together on a regional basis.

This model is used by the most successful US projects, including the Big Sky Carbon Sequestration Partnership (www.bigskyCO2.org). It involves industry leaders and scientists from six US states.

Agriculture"s involvement in the process will provide the grains industry with a higher profile and a forum in which it can influence far-reaching decisions about the future of industry and the environment, he says.

GRDC Research Code SAN00010
More information: Dr Rohan Rainbow, 08 8842 4278, admin@santfa.com.au

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