The same farming practices that promote soil conservation can also decrease the amount of CO2 accumulating in the atmosphere and threatening a global warming, according to a new issue paper by the Council for Agricultural Science and Technology (CAST). Agricultural practices that conserve soil and increase productivity while improving soil quality also increase the amount of carbon-rich organic matter in soils, thereby providing a global depository for CO2 drawn from the atmosphere by growing plants.
“We call it a win-win. Returning carbon to the soil in the form of organic matter is good agronomy. On farmed land, carbon has been released through practices that promoted organic matter oxidation, but it can be restored. An even greater opportunity for carbon storage lies in the some 2 billion hectares of desertified and degraded lands worldwide (75% in the tropics) where improved land management could benefit soil quality and hold carbon. A significant fraction of the 30% increase in atmospheric CO2 over the past 150 years stems from the breakdown of soil organic matter after forests and grasslands were cleared for farming. So there is room for it to go back,” says Norman J. Rosenberg who authored the paper along with R. Cesar Izaurralde.
There are opportunities to store carbon in soils around the world, according to Izaurralde. The soil’s storage capacity for carbon has limits, but sequestration of carbon in soils offers a unique strategic opportunity to slow global warming especially in the next 30 to 40 years while new, energy-efficient low-carbon power generation and transportation technologies are phased into use.
The CAST paper highlights results of a workshop organized by the Department of Energy’s Pacific Northwest and Oak Ridge National Laboratories in conjunction with CAST. Nearly 100 Canadian and U.S. scientists, agricultural representatives, policy makers, and others attended the workshop. New scientific opportunities were identified at the workshop to increase both the content and duration of carbon in soils. The need for inexpensive instruments and other ways of monitoring changes in soil carbon also was recognized. Workshop participants also discussed the question of what would encourage farmers to adopt practices that lead to increased soil carbon storage.
The paper indicates that there are also energy costs associated with capturing carbon in the soil — through the production, transport, and application of chemical fertilizers, manures, and pesticides; as well as the pumping and delivery of irrigation water needed to increase plant growth. But because these costs are primarily connected to food and fiber production, the resulting increase in soil carbon storage might decrease or even offset the net contribution of agriculture to global warming.
CAST is an international consortium of 38 scientific and professional societies. Its mission is to identify food and fiber, environmental, and other agricultural issues and to interpret related scientific research information for legislators, regulators, and the media for use in public policy decision making. More information on CAST and its numerous scientific reports are available at https://www.cast-science.org. Copies of the reports, including Storing Carbon in Agricultural Soils to Help Mitigate Global Warming, are available from CAST at (515) 292-2152 or by e-mail at firstname.lastname@example.org.
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