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Discussion papers | Copyright
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Original research article 06 Aug 2018

Original research article | 06 Aug 2018

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal SOIL (SOIL).

Global meta-analysis of the relationship between soil organic matter and crop yields

Emily E. Oldfield1, Mark A. Bradford2, and Stephen A. Wood1,2 Emily E. Oldfield et al.
  • 1School of Forestry and Environmental Studies, Yale University, 370 Prospect Street, New Haven, CT 06511, USA
  • 2The Nature Conservancy, Arlington, VA 22201, USA

Abstract. Resilient, productive soils are necessary to sustainably intensify agriculture to increase yields while minimizing environmental harm. To conserve and regenerate productive soils, the need to build and maintain soil organic matter (SOM) has received considerable attention. Although SOM is considered key to soil health, its relationship with yield is contested because of local-scale differences in soils, climate, and farming systems. There is a need to quantify this relationship to set a general framework for how soil management could potentially contribute to the goals of sustainable intensification. We developed a quantitative model exploring how SOM relates to crop yield potential of maize and wheat in light of co-varying factors of management, soil type, and climate. We found that yields of these two crops are on average greater with higher concentrations of SOC. However, yield increases level off at ~2% SOC. Nevertheless, approximately two thirds of the world's cultivated maize and wheat lands currently have SOC contents of less than 2%. Using this regression relationship developed from published empirical data, we then estimated how an increase in SOC concentrations up to regionally-specific targets could potentially help reduce reliance on nitrogen (N) fertilizer and help close global yield gaps. Potential N fertilizer reductions associated with increasing SOC amount to 7% and 5% of global N fertilizer inputs across maize and wheat fields, respectively. Potential yield increases of 10±11% (mean±SD) for maize and 23±37% for wheat amount to 32% of the projected yield gap for maize and 60% of that for wheat. Our analysis provides a global-level prediction for relating SOC to crop yields. Further work employing similar approaches to regional and local data, coupled with experimental work to disentangle causative effects of SOC on yield and vice-versa, are needed to provide practical prescriptions to incentivize soil management for sustainable intensification.

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Yield and SOC data from published studies E. E. Oldfield, M. A. Bradford, and S. A. Wood

Emily E. Oldfield et al.
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Publications Copernicus
Short summary
In this manuscript, we quantify the global-level relationship between soil organic matter and crop yield. We find that greater concentrations of soil organic matter are associated with greater yields, and that increases in yields saturate around 2 %. Using the relationship that we generate, we then provide an estimate of the potential for soil organic matter management to reduce global yield gaps for two of the most important staple crops (maize and wheat) grown worldwide.
In this manuscript, we quantify the global-level relationship between soil organic matter and...