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Enhanced top soil carbon stocks under organic farming

Gattinger, Andreas; Müller, Adrian; Haeni, Matthias; Skinner, Collin; Fliessbach, Andreas; Buchmann, Nina; Mäder, Paul; Stolze, Matthias; Smith, Pete; El-Hage Scialabba, Nadia and Niggli, Urs (2012) Enhanced top soil carbon stocks under organic farming. Proceedings of the National Academy of Sciences - PNAS, 109 (44), pp. 18226-18231.

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Online at: http://www.pnas.org/cgi/doi/10.1073/pnas.1209429109

Summary

It has been suggested that conversion to organic farming contributes to soil carbon sequestration, but until now a comprehensive quantitative assessment has been lacking. Therefore, datasets from 74 studies from pairwise comparisons of organic vs. nonorganic farming systems were subjected to metaanalysis to identify differences in soil organic carbon (SOC). We found significant differences and higher values for organically farmed soils of 0.18±0.06% points (mean ± 95% confidence interval) for SOC concentrations, 3.50 ± 1.08 Mg C ha−1 for stocks, and 0.45 ± 0.21 Mg C ha−1 y−1 for sequestration rates compared with nonorganic management. Metaregression did not deliver clear results on drivers, but differences in external C inputs and crop rotations seemed important. Restricting the analysis to zero net input organic systems and retaining only the datasets with highest data quality (measured soil bulk densities and external C and Ninputs), the mean difference in SOC stocks between the farming systems was still significant (1.98 ± 1.50 Mg C ha−1), whereas the difference in sequestration rates became insignificant (0.07 ± 0.08 Mg C ha−1 y−1). Analyzing zero net input systems for all data without this quality requirement revealed significant, positive differences in SOC concentrations and stocks (0.13 ± 0.09% points and 2.16 ± 1.65 Mg C ha−1, respectively) and insignificant differences
for sequestration rates (0.27 ± 0.37 Mg C ha−1 y−1). The data mainly cover top soil and temperate zones, whereas only few data from tropical regions and subsoil horizons exist. Summarizing, this study shows that organic farming has the potential to accumulate soil carbon.


EPrint Type:Journal paper
Keywords:climate change, soil quality, agricultural systems, Klima, Klimawandel
Subjects: Soil
Environmental aspects
Research affiliation: Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Sustainability > Climate Change
Switzerland > Zürich University
International Organizations > Food and Agriculture Organisation FAO
DOI:10.1073/pnas.1209429109
Related Links:http://www.fibl.org/en/themes/climate-change.html, http://www.pnas.org/content/suppl/2012/10/10/1209429109.DCSupplemental
Deposited By: Muller, Adrian
ID Code:21735
Deposited On:07 Nov 2012 09:11
Last Modified:17 Jul 2013 16:02
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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