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Accessible, affordable, fine-scale estimates of soil carbon for sustainable management in sub-Saharan Africa
Journal article   Peer reviewed

Accessible, affordable, fine-scale estimates of soil carbon for sustainable management in sub-Saharan Africa

Patrick M. Ewing, Dan TerAvest, Xinyi Tu and Sieglinde S. Snapp
Soil Science Society of America journal, Vol.85(5), pp.1814-1826
09/01/2021
DOI: https://doi.org/10.1002/saj2.20263
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https://doi.org/10.1002/saj2.20263View
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Abstract

Agriculture Life Sciences & Biomedicine Science & Technology Soil Science
Soil C status is acritical component of greenhouse gas mitigation efforts, and supports food security through affecting crop growth and management. In much of the world, laboratory-based measures of soil C are expensive and logistically challenging, whereas map-based predictions generated at the continental scale (e.g., African Soil Information Service [AfSIS]; ) may be unreliable at the management-relevant, policy-relevant, field, and regional scales. We test whether an USD 350, open source, field portable reflectometer can provide site-specific estimates of soil C status, and also predict whether a crop will respond to fertilizer across 1,155 sites in central and southern Malawi based on an established threshold of 9.4 g C kg(-1) soil. When compared with soil C measured by combustion, the scanner calibrated with covariates of field-estimable texture class and slope class provides unbiased (0.42 +/- 0.44 g C kg(-1) soil; p = .06), precise (R-2 = .57), and actionable (area under the receiver operating characteristic curve [AUC] = 0.88) data at the field scale, including at unmeasured locations (relative prediction error 19-23%) and at the village scale. The reflectometer outperformed predictions from the continental-scale AfSIS database, which were neither precise (R-2 = .044) nor actionable (AUC = 0.63) at the field scale, and underestimated soil C in the region by 2.5 +/- 0.5 g C kg(-1) soil (p < .001). The reflectometer is an accessible tool to monitor soil C in sub-Saharan Africa to improve field-level management, and guide regional policies that support food security while combating climate change.

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