An analysis of hundreds of soil samples collected from organic and conventional farms around the US shows higher average percentages both of total SOM and of humic substances – a measure of carbon sequestration – for organic farm soils compared to conventional farm soils. The mean percent humification (humic substances divided by total SOM) for organic soils is 57.3%, compared to 45.6% for conventional soils.
Ghabbour, Elham A., et al, 2017, National comparison of the total and sequestered organic matter contents of conventional and organic farm soils, Advances in Agronomy 146, https://www.sciencedirect.com/science/article/pii/S0065211317300676.
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