Initiating Greenhouse Gas Measurements on Selected WICST Treatments

Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) are greenhouse gases (GHG) that are accumulating in the atmosphere (Robertson et al., 2000; Levitus et al., 2001; Santer et al., 2003; Barnett et al., 2005). Human activities and land use practices have altered local, regional, and global C cycles (Vitousek et al., 1997). Atmospheric concentrations of CO2 have increased from 280 ppm pre-industrial concentrations (AD 1000 - 1750 [IPCC 2007]) to 385 ppm in 2008 (NOAA 2009). Most of these increases are from fossil fuel burning and land use change (IPCC 2001). In 2001, the Kyoto Protocol was expanded from recognition of C fluxes related to afforestation, deforestation and reforestation; to include terrestrial C fluxes from land management systems including forest management, crop and production systems, and revegetation (Swift, 2001). The terrestrial biosphere is a known sink for CO2 (IPCC 2001), but annual C balance is strongly dependent on management.

Agriculture plays a major role in the global flux of these gases. Management of agricultural systems has been promoted as a means to mitigate global mean radiative forcing by improving soil organic carbon (SOC) storage, decreasing CH4 emissions by promoting soil CH4 oxidation, and decreasing N2O emissions (Robertson et al., 2000). Management practices that include 1) reduced tillage, 2) reduction or split applications of nitrogen fertilizer, 3) cover crops and perennial vegetation, and 4) manipulation of animal diets, and manure handling and application all provide opportunities to reduce environmental impacts of GHG emissions (Johnson et al., 2007).

In order to understand the role agriculture, and specifically crops for biofuels, have on GHG emissions, various bio-energy productions systems (grain-based, perennial, woody, native grassland, and integrated perennial/annual crop) have been established at the Arlington Agricultural Research Station at the University of Wisconsin as part of the Great Lakes Bioenergy Research Center (GLBRC). Existing systems to be compared at Wisconsin (the WICST plots at the Arlington Research Station) have been established for 10-to-20 years and include conventionally managed continuous corn, no-till corn-soybean rotation, fertilized switchgrass monoculture, and both low (~6 species) and high (~25 species) diversity restored prairie. In the spring of 2008, the new plots were established and replicated in 5 blocks. Fluxes of GHG are measured from established cropping systems (WICST), and newly established systems (GLBRC) to compare the impact of mature systems vs. systems undergoing establishment.

Author: Gary Oates