The contentious nature of soil organic matter

Lehmann, Johannes
Kleber, Markus

¹Soil and Crop Sciences, School of Integrated Plant Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, USA
²Atkinson Center for a Sustainable Future, Cornell University, Ithaca, New York, USA
³Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon, USA
⁴Institut für Bodenlandschaftsforschung, Leibniz Zentrum für Agrarlandschaftsforschung (ZALF), Müncheberg, Germany

ⁿ¹These authors contributed equally to this work.

Received 30 April 2015; accepted 8 October 2015; Published online 23 November 2015

Author Contributions Both authors contributed equally to the concept, outline, and writing of the manuscript.

Author Information Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests. Readers are welcome to comment on the online version of the paper. Correspondence and requests for materials should be addressed to J.L. ([email protected]).

Nature 528(7580):p 60-68, December 3, 2015. | DOI: 10.1038/nature16069

The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon-climate interactions and land management.