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This article in JEQ

  1. Vol. 41 No. 4, p. 973-989
    Received: Mar 1, 2011

    * Corresponding author(s): kurt.spokas@ars.usda.gov
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Biochar: A Synthesis of Its Agronomic Impact beyond Carbon Sequestration

  1. Kurt A. Spokas *a,
  2. Keri B. Cantrellb,
  3. Jeffrey M. Novak,
  4. David W. Archerc,
  5. James A. Ippolitod,
  6. Harold P. Collinse,
  7. Akwasi A. Boatengf,
  8. Isabel M. Limag,
  9. Marshall C. Lambh,
  10. Andrew J. McAloonf,
  11. Rodrick D. Lentzd and
  12. Kristine A. Nicholsc
  1. a USDA–ARS, Soil and Water Management Unit; St. Paul, MN and Univ. of Minnesota, Dep. of Soil, Water and Climate, St. Paul, MN 55108
    b USDA–ARS, Coastal Plains Soil, Water, and Plant Research Center, Florence, SC
    c USDA–ARS, Northern Great Plains Research Lab., Mandan, ND
    d USDA–ARS, Northwest Irrigation and Soils Research Lab., Kimberly, ID
    e USDA–ARS, The Vegetable and Forage Crop Research Unit, Prosser,WA
    f USDA–ARS, Eastern Regional Research Center, Wyndmoor, PA
    g USDA-ARS, Southern Regional Research Center, New Orleans, LA
    h USDA–ARS, National Peanut Research Lab, Dawson, GA. Trade names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable. Assigned to Associate Editor Jan Willem van Groenigen


Biochar has been heralded as an amendment to revitalize degraded soils, improve soil carbon sequestration, increase agronomic productivity, and enter into future carbon trading markets. However, scientific and economic technicalities may limit the ability of biochar to consistently deliver on these expectations. Past research has demonstrated that biochar is part of the black carbon continuum with variable properties due to the net result of production (e.g., feedstock and pyrolysis conditions) and postproduction factors (storage or activation). Therefore, biochar is not a single entity but rather spans a wide range of black carbon forms. Biochar is black carbon, but not all black carbon is biochar. Agronomic benefits arising from biochar additions to degraded soils have been emphasized, but negligible and negative agronomic effects have also been reported. Fifty percent of the reviewed studies reported yield increases after black carbon or biochar additions, with the remainder of the studies reporting alarming decreases to no significant differences. Hardwood biochar (black carbon) produced by traditional methods (kilns or soil pits) possessed the most consistent yield increases when added to soils. The universality of this conclusion requires further evaluation due to the highly skewed feedstock preferences within existing studies. With global population expanding while the amount of arable land remains limited, restoring soil quality to nonproductive soils could be key to meeting future global food production, food security, and energy supplies; biochar may play a role in this endeavor. Biochar economics are often marginally viable and are tightly tied to the assumed duration of agronomic benefits. Further research is needed to determine the conditions under which biochar can provide economic and agronomic benefits and to elucidate the fundamental mechanisms responsible for these benefits.

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Copyright © 2012. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.