Greenhouse Gas Emissions from Swine Effluent Applied to Soil by Different Methods

Greenhouse gas (CO(2), CH(4), and N(2)O) emissions were measured in a field experiment evaluating preplant swine effluent application methods for no-till corn (Zea mays L.) grain production. The treatments included a control, an inorganic fertilizer treatment receiving 179 kg N ha(-1) as urea-NH(4)NO(3) (UAN), and three effluent application methods that received a target rate of 200 kg N ha(-1). The effluent treatments included surface application, direct injection, and application in combination with soil aeration. Gas emission measurements were initiated after application and collected throughout the 2007 and 2008 growing seasons using a vented chamber technique. There were no significant differences in CO(2) losses, which averaged 738 and 718 g CO(2) m(-2) in 2007 and 2008, respectively. Placement of effluent below the soil surface by injection or aeration resulted in elevated CH(4) emissions compared with the control. Injection emitted significantly more CH(4) than surface applications, with emissions of 0.26 and 0.80 g CH(4) m(-2) from the injection treatments in 2007 and 2008, respectively. In 2007, N(2)O emissions were similar for the UAN, surface effluent, and aeration effluent treatments, emitting an average of 0.72 g N(2)O m(-2). In contrast, the injection treatment emitted 0.47 g N(2)O m(-2). In 2008, this trend was reversed, with the injection treatment emitting 0.82 g N(2)O m(-2) and the remaining N source treatments emitting an average of 0.36 g N(2)O m(-2). These differences between years probably resulted from differences in rainfall distribution. These results demonstrate that climatic conditions and application method need consideration when evaluating the impact of liquid manure management on greenhouse gas emissions.