FACTBOX: Carbon farming on rise in Australia

SYDNEY Tue Jun 16, 2009 8:16pm EDT

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SYDNEY (Reuters) - Australian "carbon farmers" hope to sell their soil carbon credits in the fight against climate change. Australia plans to have an Emissions Trading Scheme (ETS) running by 2011, with agriculture possibly included in 2015.

Here are some facts about soil carbon, carbon sequestration, carbon farming:

SOIL CARBON SEQUESTRATION

The uptake and storage of carbon. Trees and plants, for example, absorb carbon dioxide, release the oxygen and store the carbon. Fossil fuels were at one time biomass and continue to store the carbon until burned.

By 2030 an estimated 5.5-6 gigatonnes of CO2 equivalent a year could be mitigated by agriculture, with about 89 percent achieved by soil carbon sequestration through cropland and grazing management and restoration of organic soils, said a U.N. climate change paper on agriculture in November 2008.

HOW IS SOIL CARBON PRODUCED

Soil carbon is created when CO2 is absorbed by vegetation, oxygen is released and carbon is used to make living tissue, such as vegetation.

It is also produced by microbes and fungi, stimulated by plant roots as they push down through soil, retreating when the foliage above ground is grazed or harvested, then pushing down through the soil again as the foliage regrows.

Much of the carbon taken in by plants enters the top layer of the soil and is held there as humus. Some of it is carried further down to deeper layers of the soil where it can be held for hundreds of years.

Some carbon returns to the atmosphere as CO2 from respiration of plants and some as methane from the rotting of vegetation.

WHAT IS CARBON FARMING

Carbon farming is a new way to describe a collection of eco-friendly farming techniques which increase soil organic carbon in agricultural land.

The farming practices include:

1. One hundred percent groundcover to prevent soil being blown or washed away: Cooler soil is more attractive to microbes. Farmers avoid overgrazing and burning grasses.

2. Grazing management: Stock are concentrated in small paddocks for short periods (days) so they graze evenly and also till the soil with their hooves, stomping old grass and manures into the soil. When plants are lightly grazed the plants roots go deeper into the soil helping to create more carbon.

3. No till cropping/conservation tillage: Farmers abandon plowing and plant seeds by dropping them into ruts which barely disturb the soil. Not disturbing the soil avoids releasing soil carbon.

4. Pasture cropping: Planting and growing crops amongst native grasses and weeds, taking advantage of the native vegetations dormant period to grow and harvest crops. This ensures all-year ground cover of soil and more microbes.

5. Biological farming: Zero chemical fertilizers.

6. Mulching" Covering bare paddocks with hay or dead vegetation. This protects soil from the sun and allows the soil to hold more water and be more attractive to microbes.

(Sources: Carbon Farmers of Australia, www.carbonfarmersofaustralia.com.au; Prime Carbon, www.primecarbon.com.au)

(Editing by Megan Goldin)

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