Management of Dryland Cropping Systems in the U.S. Great Plains: Effects on Soil Organic Carbon

The expansion and intensification of agroecosystems worldwide has significantly affected the environment at multiple spatial scales (Matson et al., 1997). Agroecosystem effects on atmospheric constituents have altered local, regional, and global environmental quality through windblown soil (Zhang et al., 2001) and emission of particulate matter, reactive N (e.g., NH3 and NOx), volatile organic compounds, hydrogen sulfide, and greenhouse gases (GHGs) (Aneja et al., 2006; Franzluebbers and Follett, 2005). The contribution of agroecosystems to GHG emission, in particular, has received increased international attention given the role of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) to increase radiative forcing of the Earth’s atmosphere (IPCC, 2007), which is the underlying cause of global climate change (Oreskes, 2004; Brown, 2006). Projected changes in climate from elevated concentrations of GHGs in the Earth’s atmosphere include increased mean global temperatures of 1.5 to 4.5°C (Mahlman, 1997), shifts in vegetation zones toward the poles (or disappearance entirely, due to sea level rise), and a more vigorous hydrological cycle (Rosenzweig and Hillel, 1998). Such projections do not portend well for agriculture and will require the development of resilient agroecosystems to meet future demand for food, feed, and fiber. Mitigation of GHG emission from agroecosystems requires increasing soil organic carbon (SOC), decreasing CH4 and N2O emissions, or increasing soil CH4 oxidation (Robertson et al., 2000; Mosier et al., 2003). To date, much emphasis