Emerging land use practices rapidly increase soil organic matter
Machmuller, Megan B., Marc G. Kramer, Taylor K. Cyle, Nick Hill, Dennis Hancock, and Aaron Thompson. 2015. "Emerging land use practices rapidly increase soil organic matter."  Nature Communications 6:6995. doi: 10.1038/ncomms7995

Key Takeaways

  • This paper, published in Nature, reports one of the highest carbon drawdown rates ever documented for grazing - 8 tons per hectare (3.2 tons per acre) per year.
  • The high C capture in soil occurs through a conversion from row cropping to “management-intensive grazing.” (Note: this is not the same as Holistic Management, but we include this paper to show the positive effects of converting croplands back to pasture)
  • Cation exchange and water holding capacity also increased by 95% and 34%, respectively.
  • The study was conducted on farms in Georgia, USA, where the average annual precipitation is 1,224 millimeters (48 inches).

Summary

The loss of organic matter from agricultural lands constrains our ability to sustainably feed a growing population and mitigate the impacts of climate change. Addressing these challenges requires land use activities that accumulate soil carbon (C) while contributing to food production. In a region of extensive soil degradation in the southeastern United States, we evaluated soil C accumulation for 3 years across a 7-year chronosequence of three farms converted to management-intensive grazing. Here we show that these farms accumulated C at 8.0 Mg ha−1 yr−1, increasing cation exchange and water holding capacity by 95% and 34%, respectively. Thus, within a decade of management-intensive grazing practices soil C levels returned to those of native forest soils, and likely decreased fertilizer and irrigation demands. Emerging land uses, such as management-intensive grazing, may offer a rare win–win strategy combining profitable food production with rapid improvement of soil quality and short-term climate mitigation through soil C-accumulation.

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