SOIL ORGANIC MATTER AND NUTRIENT CYCLING TO SUSTAIN AGRICULTURE IN THE SOUTHEASTERN USA
Location: Athens, Georgia
Title: Soil quality and organic carbon sequestration with improved pasture management
Submitted to: Proceedings of the National Conference on Grazing Lands
Publication Type: Proceedings
Publication Acceptance Date: October 21, 2009
Publication Date: June 1, 2010
Citation: Franzluebbers, A.J. 2010. Soil quality and organic carbon sequestration with improved pasture management. 4th National Conference on Grazing Lands, December 13-16, 2009, Sparks, Nevada. CD-ROM.
Interpretive Summary: Pasture management has the potential to build soil fertility, restore soil functions, and mitigate greenhouse gas emissions through surface soil organic matter accumulation. A scientist from the USDA Agricultural Research Service in Watkinsville Georgia summarized recent literature from the humid region of the eastern USA on how pastures affect soil quality and soil organic carbon. Establishment of perennial grass pastures in the southeastern USA can sequester soil organic carbon at rates of 0.1 to 0.5 tons C / acre / year. Soil organic carbon sequestration rate is affected by forage type, fertilization, forage utilization, animal behavior, and soil sampling depth. It can also be spatially affected by animal behavior and by soil depth. Soil organic carbon storage under pastures is important for improving water relations, fertility, and soil quality. With 111 million acres of agricultural land in the southeastern USA, 113 million tons of CO2 / year could be reasonably calculated as potentially sequestered in soil organic matter. Landowners in the eastern USA have great potential to restore soil fertility and mitigate greenhouse gas emissions with adoption of and improvement in pasture management systems.
Improved pasture management systems are needed to restore soil quality, sequester soil organic C, and build the productive capacity of soils in grassland environments so that (1) precipitation can be effectively utilized by plants, (2) water runoff and contaminant transport can be minimized, (3) natural nutrient cycling processes can be restored to rejuvenate long-term fertility, and (4) productive capacity of soils can be fully realized to produce the food, feed, fiber, and fuel needs of the future. Grazing lands in the eastern USA are managed primarily for introduced plant species that have high forage production potential or that fit a niche with a farming system. Moderate grazing of pastures may be the most effective strategy for storing soil organic C, because return of dung to the soil surface has positive effects on soil surface properties, including soil microbial biomass and mineralizable C and N. Grazing land managed with moderate grazing pressure, i.e., utilizing forage to an optimum level without compromising regrowth potential, can (1) provide economic opportunities with low risk for landowners, (2) improve degraded land by building soil fertility, (3) improve water utilization and quality within the landscape, and (4) help mitigate the greenhouse effect by storing C in soil as organic matter. Literature in the eastern USA was reviewed to illustrate the effect of improved pasture management on soil quality and soil organic C sequestration. Implications of soil organic C sequestration for C trading and provision of ecosystem services are discussed.