BRENDON CANT brendon at iinet.net.au
Wed Apr 23 03:04:38 CEST 2008

TIMES OF CHANGE ON THE CLIMATE FRONT 23.4.08<?xml:namespace prefix = o ns =
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As time passes, language evolves to accommodate new words and phrases to
describe new developments and situations.


Phrases such as carbon sequestration, greenhouse gas (GHG) emissions and
carbon trading are a few that come to mind and are now used to discuss
climate change and its influence on the agricultural sector.


Carbon in Australian cropping soils, which are naturally dynamic and
cyclical, is increased by inputs of organic matter and is highly dependent
on plant growth, soil microbial activity and seasonal conditions.


Total soil carbon is affected by farming practices and natural events such
as drought or heavy rainfall. Drought, for example, causes carbon loss
through soil surface exposure and lowered inputs from biomass.


The Australian agricultural sector in general and grains industry in
particular, are net emitters of GHGs.


Worth noting is that emissions have decreased markedly in recent years with
reduced tillage and fuel use and better nitrogen fertiliser management.


A paper presented by Alan Umbers of the GRDC Farming Practices Initiative at
the GRDC-supported 2008 WA Agribusiness Crop Updates, provided a
‘big-picture’ view of soil carbon from soil element to tradable commodity.


Australian rainfed cropping soils are generally low in carbon – frequently
about one per cent in the top 10 centimetres.


Significant amounts of organic matter must be annually added to increase
soil organic carbon substantially above these levels.


However, sequestration of soil carbon is not infinite – a new equilibrium
level is reached after perhaps 20 to 30 years – based on the cyclical nature
of carbon, where farming practices and systems determine the balance.


Understanding soil carbon dynamics and the other greenhouse gas of interest,
nitrous oxide, is difficult in a biological system such as grain production.


According to Mr Umbers’ research, where there is high biomass production,
perennials in the system and more than 550 millimetres of annual rainfall,
soil carbon can increase with conservation farming practices. Most of
Australia’s grain crops are in drier areas.


Finally, he cautions growers interested in carbon trading schemes, as
emissions and sequestration will be considered and participants may need
contracts to verify their sequestration and emission levels.




The Crop Doctor is GRDC Managing Director, Peter Reading, Tel 02 6166 4500

Further Information: Alan Umbers, Tel 0428 432 557

GRDC REF: CDMar082.doc/Blumenthal200308


Brendon Cant & Associates
Public Relations & Marketing 
Suite 5
4 Gugeri St
Claremont WA 6010
Tel 08 9384 1122


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