Long-term cropping systems field plots were established in 2002 in west central Minnesota to compare tillage, rotation and fertilizer treatments and to identify and develop economically-viable and environmentally-sustainable farming systems. It is hypothesized that minimized tillage and diversified crop rotation can improve soil quality and enhance sustainability. As part of the USDA-Agricultural Research Service, Greenhouse gas Reduction through Agricultural Carbon Enhancement (GRACEnet) project, greenhouse gas emission was monitored in a subset of treatments. Treatments were selected to represent three different scenarios: "business as usual," "maximum C sequestration" and "optimum greenhouse gas benefits." The "business as usual" scenario has conventional tillage (chisel or moldboard plow), and receives high fertilizer inputs in a corn-soybean rotation. The "maximum C sequestration" scenario is strip tilled with a mole-knife, and receives high fertilizer inputs in a corn-soybean-wheat/alfalfa-alfalfa rotation. The "optimum greenhouse gas benefits" scenario is strip tilled with a mole-knife but receives no fertilizer inputs in a corn-soybean-wheat/alfalfa-alfalfa rotation. Nitrous oxide and carbon dioxide emission have been monitored using vented static chambers, since April 2004, methane since March 2005. Collateral information collected included weather data, soil temperature and volumetric soil moisture at time of sampling. Two collars were installed in each plot sampled: for row crops, one collar was positioned adjacent to the row and the second collar was in the inter-row; in wheat and alfalfa, collars were positioned randomly with regard to plants. A total of 40 plots (80 collars) were sampled typically every other week. The greatest nitrous oxide flux occurred during spring thaw events, which accounted for 33% to 55% of the flux for 2005 and 2006. Additional events corresponded primarily to nitrogen fertilizer events. Under these managements the soil tended to be neutral to slight methane sinks. Economic and environmental impact among the scenarios will be compared.