Agronomy Library > Soil Conservation

Sequestering Carbon in Cropland - Direct Seeding Advantage 2004
Author: Mark A. Liebig, USDA-ARS, Northern Great Plains Research Laboratory
Date Created: November 23, 2004
Last Reviewed: November 23, 2004

Introduction
Since the beginning of the 19th century the concentration of carbon dioxide (CO2) in the earth’s atmosphere has increased from about 280 ppm to a current value of 376 ppm (Keeling and Whorf, 2004). Much of this increase has been attributed to the industrialization of human society, which has increased in population from 1.1 to 6.4 billion during the same time period (U.S. Census Bureau, 2004). Because CO2 is a greenhouse gas, it has been implicated in global climate change. A doubling of atmospheric CO2 over pre-industrial levels is predicted to lead to global warming from 1.5 to 4.5°C (Mahlman, 1997). This magnitude of change in temperature could result in movement of vegetation zones poleward and increase the frequency of severe weather events (Rosenzweig and Hillel, 1998). 

Reducing emissions of CO2 and other greenhouse gases is a primary strategy to mitigate global climate change. Increasing the quantity of carbon sequestered in soils and biomass, however, is another important strategy, and one directly affected by agricultural management. 

Management effects on carbon accumulation or loss in soil are expressed through two key metabolic processes: photosynthesis and respiration. Carbon dioxide is assimilated by plants via photosynthesis and – at least temporarily – sequestered in biomass and soil. Conversely, CO2 is released back to the atmosphere as an end product of respiration by soil fauna and flora. Carbon dioxide uptake and emission are not tightly linked in most agroecosystems, so knowledge of both processes is required to understand soil carbon dynamics and how it is affected by management. This paper will provide a brief review of management effects on soil carbon sequestration for cropping systems in semiarid regions of northwestern USA and western Canada. 

This region includes agricultural land recognized throughout the world for its inherently fertile soils, which contribute to the production of large quantities of grain and forage in spite of highly variable climatic conditions.

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