How do changes in bulk soil organic carbon content affect carbon concentrations in individual soil particle fractions?

X. M. Yang,J. Y. Yang,C. F. Drury,W. D. Reynolds

doi:10.1038/srep27173

X. M. Yang, J. Y. Yang + Show 2 more

Open Access

https://doi.org/10.1038/srep27173

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Journal: Scientific Reports	Publication Date: Jun 1, 2016
Citations: 16	License type: CC BY 4.0

Affiliation: Agriculture and Agri-Food Canada

Abstract

We test the common assumption that organic carbon (OC) storage occurs on sand-sized soil particles only after the OC storage capacity on silt- and clay-sized particles is saturated. Soil samples from a Brookston clay loam in Southwestern Ontario were analysed for the OC concentrations in bulk soil, and on the clay (<2 μm), silt (2–53 μm) and sand (53–2000 μm) particle size fractions. The OC concentrations in bulk soil ranged from 4.7 to 70.8 g C kg−1 soil. The OC concentrations on all three particle size fractions were significantly related to the OC concentration of bulk soil. However, OC concentration increased slowly toward an apparent maximum on silt and clay, but this maximum was far greater than the maximum predicted by established C sequestration models. In addition, significant increases in OC associated with sand occurred when the bulk soil OC concentration exceeded 30 g C kg−1, but this increase occurred when the OC concentration on silt + clay was still far below the predicted storage capacity for silt and clay fractions. Since the OC concentrations in all fractions of Brookston clay loam soil continued to increase with increasing C (bulk soil OC content) input, we concluded that the concept of OC storage capacity requires further investigation.

Highlights

(g C kg−1 bulk soil) considering a single soil type with a large range of organic carbon (OC) concentrations resulting from a range of long-term soil and crop management practices
The concentration of OC associated with particle size fractions on a bulk soil basis ranged from 0.1 to 28.3 g C kg−1 bulk soil for sand, 0.6 to 20.7 g C kg−1 bulk soil for silt, and 2.9 to 28.9 g C kg−1 bulk soil for clay, with the averaged values of 1.8, 7.1 and 11.8 g C kg−1 bulk soil, respectively
From the perspective of increasing bulk soil carbon levels over time, the clay sized particles would become saturated with C far before the silt particles, while the OC in the sand sized particle would continue to increase as bulk soil OC increases (Fig. 1, Table 2)

Summary

Introduction

(g C kg−1 bulk soil) considering a single soil type with a large range of OC concentrations resulting from a range of long-term soil and crop management practices. Soil samples were collected from several long-term field trials on a Brookston clay loam, and relationships among OC storage in bulk soil and on the clay (53 μm) particle size fractions were studied.

Results

Conclusion