Agricultural, forestry practices can increase carbon sequestration
Agriculture alone may not be able to mitigate global climate change, but certain practices can make a positive difference and in some cases, are cost-saving to producers, according to Chuck Rice, who is a University Distinguished Professor at Kansas State University.
Several agricultural and forestry practices can increase carbon sequestration, said Rice, who leads a team of scientists at 10 universities that comprises the Consortium for Agricultural Soils Mitigation of Greenhouse Gasses (CASMGS). He briefed members of the Senate Agriculture Committee in March and a Congressional committee of House and Senate members in April on the topic.
Rice, who is an agronomist, described the carbon sequestration practices that can be implemented on U.S. farms, including what they are and how they work:
--Continuous no-till: Producing crops without tilling the soil. There are variations on this, such as strip-till, reduced tillage, and ridge-till, but the research on whether those variations can sequester carbon is mixed. When soil is tilled, air is mixed into the soil and organic matter is oxidized by soil microbes, releasing a portion of the stored soil carbon. By avoiding all tillage, no-till production avoids oxidizing organic matter, so more of the plant organic carbon remains in the soil every year. Tillage also makes the soil more susceptible to water and wind erosion, and the organic fraction of the soil is especially vulnerable to these losses. Also, no-till farming reduces fuel use, which cuts CO2 emissions. Applying manure to the soil, along with no-till farming, often results in even greater levels of carbon sequestration.
--Increased crop biomass production: Producing more biomass per acre per year. Examples include the production of higher crop or forage yields, more intensive rotations, cover crop production, elimination of unplanted fallow periods, and the use of higher residue crops, such as corn, grain sorghum, and wheat.
More plant production leads to more carbon being fixed by the plants into organic materials in roots, stems, leaves, and seed. Part of this organic carbon remains in the soil, and eventually becomes incorporated into soil organic carbon. When fields are fallowed, no crop is produced and this reduces the amount of plant material entering the soil system. Continuous cropping, or using cover crops to replace fallow, keeps plant material production at the highest possible level, increasing soil carbon levels.
--New grass plantings: Any new perennial grass plantings, such as Conservation Reserve Program ground, new pasture ground, reclaimed land, grass waterways, and buffer strips. Perennial grass plantings establish long-term areas of plant material on soil that is undisturbed by tillage. Grasses incorporate considerable carbon into the soil through photosynthesis, and the production of roots and stems in the soil. This organic material eventually decomposes and adds to the soil organic carbon pool in the soil. As grass stands mature over a period of 20 to 30 years, they reach a natural equilibrium in which carbon input through photosynthesis is balanced by carbon emissions through respiration.
--Soil conservation practices: Terraces, grass waterways, buffer strips, and any other soil erosion prevention measure. Soil conservation doesn't sequester new soil carbon. Rather, it prevents the loss of existing soil organic carbon. Soil erosion, both water erosion and wind erosion, exposes organic materials in the soil to oxygen. This can result in oxidization of the organic material, and the release of CO2 into the atmosphere.
--Improved grazing land management methods: Regular use of proper grazing methods and properly timed prescribed burning for certain grass species to increase forage production. The goal is to increase
forage production, which will increase the amount of plant organic carbon production and result in an increase in soil organic carbon. Another practice grazing land managers can do is to improve grazing distribution if there are areas of the grazing land that are eroded by animals. This will help protect existing soil carbon levels by reducing soil erosion.
More information about carbon sequestration, including the role agriculture can play and economic implications, is available on the K-State website http://www.soilcarboncenter.k-state.edu or the CASMGS site http://www.casmgs.colostate.edu.