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The contentious nature of soil organic matter

Abstract

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.

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Figure 1: Traditional and emergent views of the nature of soil organic matter affect how we predict and manage soil, air and water.
Figure 2: Reconciliation of current conceptual models for the fate of organic debris into a consolidated view of a SCM of organic matter cycles and ecosystem controls in soil.
Figure 3: Weighing up the empirical information supporting either the historic or evidence-based interpretation of the nature of soil organic matter.

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

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Lehmann, J., Kleber, M. The contentious nature of soil organic matter. Nature 528, 60–68 (2015). https://doi.org/10.1038/nature16069

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