Agroecosystem Management Effects on Greenhouse Gas Emissions Across a Coastal Plain Catena

Landscape variability influences soil properties that influence soil respiration and subsequent trace gas emissions. Scarcity of data on greenhouse gas emissions as influenced by landscape variability and agroecosystem management in southeastern United States necessitates study. The objective of this study was to evaluate effects of landscape variability and agroecosystem management on methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions on. a Coastal Plain catena (Typic, Oxyaquic, and Aquic Paleudults) in Alabama. Soil management strategies included (i) conventional tillage (CT), (ii) conservation tillage (CsT), (iii) CT with dairy manure (CTM), and 4) CsT with dairy manure (CsTM) on a corn (Zea mays L.)-cotton (Gossypium hirsutum L.) rotation. Each soil management treatment was replicated on summit, sideslope, and the drainageway landscape position. Gas measurements were conducted using a closed chamber method. The drainageway emitted 46, 251, 59, and 185 mg CH4-C ha(-1) h(-1) from CT, CTM, CsT, and CsTM treatments, respectively The summit position had fluxes of -59 and -90 mg CH4-C ha(-1) h(-1) on CT and CsT treatments, respectively. Averaged across seasons, CT and CsT N2O fluxes were similar (547 and 437 mg N2O-N ha(-1) h(-1), respectively) in the drainageway landscape position. Winter 2005 CO2 emission from CsT treatments (averaged across landscape positions) was 1304 g CO-C compared with 227 g ha(-1) h(-1) CO2-C from CT treatments.