Increasingly it is clear that efforts to reduce greenhouse gas emissions – while absolutely necessary – are not enough to address the climate change that is already under way. Now it is urgent that we implement measures to pull carbon from the atmosphere and store it safely, deep beneath the surface of the soil, utilizing photosynthesis and other natural systems that are already proven and at hand. See a report on the net climate benefit of rotational grazing here.
Plowing allows carbon to oxidize and contribute to climate change.
For decades farmers in the US have plowed up ground to plant corn, which has allowed soil carbon near the surface to oxidize. About 40% of this corn is used for livestock feed. To reverse the damage done by industrial agriculture, we must adopt a holistic management approach to managing pasture. Grazing ruminants can enhance carbon sequestration. Proper grazing management can result in greater soil carbon concentrations than non-grazed systems.
This photo shows soil samples 50 centimeters deep (almost 20 inches) taken from two pieces of land divided only by a fence. The levels of carbon in both pieces were originally the same, but changed dramatically after two brothers subsequently managed their respective pieces in different ways for 10 years.
The sample on the left was taken from the piece that was managed with rotational grazing and other practices that allow maximum photosynthesis; this sample shows that 50 centimeters of carbon-rich topsoil formed in the 10-year period. On the land represented by the sample on the right, photosynthesis was held back by applications of super-phosphate fertilizer, removal of perennial ground cover, and conventional grazing management. (Photo courtesy of Dr. Christine Jones, soils ecologist.)
Nature does the work of building topsoil and sequestering carbon from the bottom up. Rotational grazing of cattle on perennial pasture allows the plants to form deep roots. As the plants take in carbon from the air, microbes in and around the roots pass some of that carbon from the plants to the soil, and also transfer essential minerals to the plants. This phenomenon is called bidirectional flow.
Also, grazing plants results in significant percentages of roots being shed as the plants re-establish an equilibrium between their leaf and root areas; these cast-off roots add carbon and feed soil microorganisms.
We can combat climate change by these grazing practices:
- Raise cattle on pasture only, in a rotation of paddocks that allows the pasture plants to grow tall; the roots will go correspondingly deep.
- Allow the herd to move to a new paddock frequently; the numbers of animals per acre can be large, as long as they are moved in a timely way that benefits both the cattle and renewed plant growth.
- Allow uncut or trampled grass to continue photosynthesis.
- Before cycling the herd back to a paddock that has been grazed, let the paddock rest so that the grass grows tall again and the stems have three leaves.
- Disturb the soil as little as possible to allow microbial life to transfer carbon from the plant roots to the soil; for cover crops use a no-till seeder.
- In cold climates, allow some paddocks to remain uncut after mid-summer for grazing in the winter.
- To extend the season at both ends, plant cover crops that have a longer growing season than perennial pasture.
- Do not use pesticides and herbicides such as glyphosate (Roundup), which destroy microbial soil life;
- Do not use chemical fertilizers, which accelerate carbon loss from the soil.
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