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ARS Home » Midwest Area » Morris, Minnesota » Soil Management Research » Research » Publications at this Location » Publication #114943
Title: CHARCOAL CARBON IN U.S. AGRICULTURAL SOILS

Author
item SKJEMSTAD, JAN - CSIRO AUSTRALIA
item Reicosky, Donald
item Wilts, Alan
item MCGOWAN, JANINE - CSIRO AUSTRALIA

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: The increase in carbon dioxide in the atmosphere has attracted interest due to potential global warming and the prospects of using the soil as storage for carbon released by other human activity. High levels of charcoal carbon resulting from repeated historical burning of grasslands, open woodlands and agricultural crop residues have been reported in soils from Australia and Germany. In this study, five U.S. soils were selected from long-term research plots in widely-different agricultural areas. The charcoal carbon content was estimated on each soil using sophisticated methods. These analyses showed that all five soils contained measurable amounts of charcoal carbon, and constituted up to 35% of the soil total organic carbon. The charcoal material had a plant-like morphology but was blocky and had fractured edges. The implications of this charcoal material, which must be highly resistant to microbiological decomposition, to the soil carbon cycle and issues such as greenhouse gas emissions from soil are important. The processes of charcoal formation, its biological, physical and chemical properties and distribution in many soils are largely unknown and require further study. Understanding the role of charcoal in nutrient cycling and C sequestration is vital for understanding the role and minimizing the impact of agriculture on climate change. This information will impact scientists around the world by allowing them to identify important forms of carbon and potential impact on global climate change. These results are significant to farmers and policy makers because carbon credits require understanding the function and form of soil carbon. This information will be of direct benefit to the farmers to enable them to maintain crop production with minimal impact on the environment.

Technical Abstract: High levels of charcoal carbon resulting from repeated historical burning of grasslands, open woodlands and agricultural crop residues have been reported in soils from Australia and Germany. In this study, five U.S. soils were selected from long-term research plots in widely different agricultural areas. The charcoal carbon content was estimated on each soil using a combination of physical separation, high-energy photo-oxidation an solid-state **13C nuclear magnetic resonance spectroscopy. These analyses showed that all five soils contained measurable amounts of charcoal carbon, <53 um in size and ranging from 1.8 to 13.6 g C kg**-1 soil and constituted up to 35% of the soil total organic carbon. Scanning electron microscopy showed that the charcoal material had a plant-like morphology but was blocky and had fractured edges. These particles were similar in morphology to those separated from Australian and German soils. The implications of this charcoal material, which must be highly resistant to microbiological decomposition, to the soil carbon cycle and issues such as greenhouse gas emissions from soil are discussed. The processes of charcoal formation, its biological, physical and chemical properties and distribution in many soils are largely unknown and require further study. Understanding the role of charcoal in nutrient cycling and C sequestration is vital for understanding the role and minimizing the impact of agriculture on climate change.