Banner
    Before Selling Carbon Credits, Read This
    By News Staff | May 18th 2007 02:00 AM | 3 comments | Print | E-mail | Track Comments
    Storing carbon in agricultural soils presents an immediate option to reduce atmospheric carbon dioxide and slow global warming. Farmers who adopt practices that store carbon in soil may be able to "sell" the stored carbon to buyers seeking to offset greenhouse gas emissions. Before farmers can sell carbon credits, however, they need to be able to verify that changing soil management has increased the soil organic carbon (SOC) in their fields.



    Researchers at Montana and Colorado State Universities now have evidence that a soil model can be used to accurately estimate carbon levels in soil under certain climate and land conditions. By using this model, farmers and landowners will be able to verify soil carbon change for carbon trading. Scientists report their findings on the reliability of the Century soil model in the May-June 2007 issue of the Soil Science Society of America Journal.

    Funding for this research was provided by the Upper Midwest Aerospace Consortium-Public Access Resource Center, the Consortium for Agricultural Soils Mitigation of Greenhouse Gases, and the Montana State University Agricultural Experiment Station.

    "The Century model estimates soil organic carbon content and soil organic carbon change using soil texture, weather, and farm management information," said Ross Bricklemyer, lead author of the study.

    Working together with farmers from Montana, researchers compared Century model estimates of soil carbon storage to field SOC measurements. Scientists measured carbon storage and soil texture in 10 paired fields under no-till and conventional-till management. They estimated the increase in carbon stored under no-tillage adoption as the difference between carbon levels in no-till and till fields. They then compared the soil carbon values predicted by the Century model to measured SOC and SOC rate of change.

    The Century model accurately predicted SOC content and rate of carbon change, however, differences between measured soil texture data and state and county soil texture maps greatly influenced carbon storage estimates.

    "The accuracy and scale of soil texture data highly influence the accuracy of Century model estimations of soil carbon," said Bricklemyer. "The model accurately estimated soil carbon content and the influence soil clay content had on the amount of carbon in the soil."

    Although texture was important in determining SOC storage estimates, the effect of no-tillage management on the rate of carbon storage was not influenced by texture in this study. Some scientists have found that high clay content, or heavy soils, store carbon more rapidly under no-tillage management than soils with little clay content, others have found that clay content has no affect on carbon storage rates under no-tillage practice.

    Bricklemyer says that because the effects of clay content on the rate of soil carbon under no-tillage change are not well understood by the research community, clay content information was not directly used by the Century model for carbon change calculations.

    "This study also points out the importance of establishing benchmark monitoring sites, under actual farm conditions, where soil texture, soil carbon and other soil properties can be accurately measured and re-measured over time," said Bricklemyer. "Such a system, which currently doesn't exist in the U.S., would help us improve and validate estimates of carbon sequestration over time."

    Comments

    Cash
    They sound well meaning and all, but the 90% of the carbon credit market that is a scam - including one prominent "Inconvenient Truth" politician who owns a company and sells them to himself to offset his 29,000 square foot house - make this whole industry about as reputable as horse racing.

    A model that predicts soil carbon: what's not to love in this news release? The closing paragraph, where it says:

    "This study also points out the importance of establishing benchmark monitoring sites, under actual farm conditions, where soil texture, soil carbon and other soil properties can be accurately measured and re-measured over time," said Bricklemyer. "Such a system, which currently doesn't exist in the U.S., would help us improve and validate estimates of carbon sequestration over time."

    Doesn't exist? This statement from another Century model user puts it a little more diplomatically:

    CENTURY is used to simulate soil organic matter dynamics at points used by the National Resource Inventory (NRI), a nationally-representative two-stage area sample, for which a standard design-based variance estimator provides a consistent estimate of uncertainty. At these NRI points, detailed soils data and cropping history are available, but tillage, mineral fertilizer use and organic amendments are not.

    Why not simply port (NRI) "established benchmark monitoring sites" to do this job? It is hard to conceive that anyone involved with farm soil carbon issues could be unaware of the significance of the NRI. Are we hearing the distant din of clashing cultures, in this case the clash of academic and government agency cultures on the competitive field of GHG funding?

    The NRI tracks USA farm soil carbon and was used to figure out national soil carbon storage figures. True, the NRI doesn't yet gather information on tillage or fertilization, but it could. And it should.

    Note: The published study referred to in the news release, Sensitivity of the Century Model to Scale-Related Soil Texture Variability, is pay wall embargoed until November, 2008.

    I would think there is enormous difficulty in obtaining a representative sample.In any case a trees capacity to remove co2 from the atmosphere depends on many things,is directly proportionate to the level of co2 in the environment,the higher the co2 the faster it will be removed by the tree.The carbon content already in the soil and nitrogen by which the tree can synthesize protein from which it gains its energy for growth and again the faster the growth the faster co2 will be removed.Carbon content of soil can be increased by importation of carbon e.g. lignite,a fossil fuel and peat without it coming from the atmosphere.The best test for whether carbon is being removed from the atmosphere is to test the protein content of the food grown in it . If overall it is high then it is certain that co2 is being removed from the atmosphere as quickly as possible.It is by rewarding high protein content in food that will ensure the quickest removal of co2 from the atmosphere.The burning or direct sequestration of fossil fuels will only aid this process as it will increase plant growth rates merely planting more trees that grow slowly will not.