title: Fertilizer source and tillage effects on yield-scaled nitrous oxide emissions in a corn cropping system.
abstract: Management practices such as fertilizer or tillage regime may affect nitrous oxide (N₂O) emissions and crop yields, each of which is commonly expressed with respect to area (e.g., kg N ha or Mg grain ha). Expressing N₂O emissions per unit of yield can account for both of these management impacts and might provide a useful metric for greenhouse gas inventories by relating N₂O emissions to grain production rates. The objective of this study was to examine the effects of long-term (>17 yr) tillage treatments and N fertilizer source on area- and yield-scaled N₂O emissions, soil N intensity, and nitrogen use efficiency for rainfed corn ( L.) in Minnesota over three growing seasons. Two different controlled-release fertilizers (CRFs) and conventional urea (CU) were surface-applied at 146 kg N ha(-1) several weeks after planting to conventional tillage (CT) and no-till (NT) treatments. Yield-scaled emissions across all treatments represented 0.4 to 1.1% of the N harvested in the grain. Both CRFs reduced soil nitrate intensity, but not N₂O emissions, compared with CU. One CRF, consisting of nitrification and urease inhibitors added to urea, decreased N₂O emissions compared with a polymer-coated urea (PCU). The PCU tended to have lower yields during the drier years of the study, which increased its yield-scaled N₂O emissions. The overall effectiveness of CRFs compared with CU in this study may have been reduced because they were applied several weeks after corn was planted. Across all N treatments, area-scaled N₂O emissions were not significantly affected by tillage. However, when expressed per unit yield of grain, grain N, or total aboveground N, N₂O emissions with NT were 52, 66, and 69% greater, respectively, compared with CT. Thus, in this cropping system and climate regime, production of an equivalent amount of grain using NT would generate substantially more N₂O compared with CT.
authors.affiliation: USDA-ARS, Soil and Water Management Unit., Paul, MN 55108, USA. venterea@umn.edu
authors.forename: Rodney T
authors.initials: RT
authors.lastname: Venterea
authors.forename: Maharjan
authors.initials: M
authors.lastname: Bijesh
authors.forename: Michael S
authors.initials: MS
authors.lastname: Dolan
mesh_terms: D002980:Climate; D018556:Crops, Agricultural; D005308:Fertilizers; D009609:Nitrous Oxide / Q000032:analysis*; D012987:Soil; D003313:Zea mays
chemical_list: D005308:Fertilizers; D012987:Soil; D009609:Nitrous Oxide