76-3 Nitrous Oxide Emissions From Arable Soil: Effects of Crop Rotation, Tillage and Manure Management.



Monday, October 17, 2011: 4:00 PM
Henry Gonzalez Convention Center, Room 207A, Concourse Level

Soren Petersen, Department of Agroecology and Environment, University of Aarhus, Tjele, Denmark
Soil carbon storage and nitrous oxide (N2O) emissions are both important for the greenhouse gas balance of agricultural soil, but difficult to verify under field conditions due to high spatial and temporal variability. Emissions of N2O from arable soil are derived mainly from the short-term (<1 yr) turnover of fertilizers, manure and crop residues, which indicates that mitigation options may be found with a better understanding of management effects on soil C and N cycling and N2O emissions. This presentation will describe N2O studies within long-term crop rotation experiments which allow side-by-side comparisons of contrasting management strategies. A tillage experiment on a sandy loam soil, established in 2002, was used to study effects of residue management and tillage, and interactions with manure, on N2O emissions. With removal of crop residues there was no difference between three tillage strategies, but with residue retention there was significantly higher N2O emission from ploughed soil compared to non-inversion tillage. Cover crops are particularly needed in organic farming systems where the N supply is limited. Another long-term experiment with eight four-crop rotations was established on three soil types in 1996 to investigate strategies to improve crop yields. Estimates of N2O emission from the same crop (winter wheat) in four different rotations, and from all crops (winter wheat, grass-clover, spring barley, potato) of a selected rotation, suggest that emissions should be considered at the crop rotation level. Although short-term N2O emissions appear to be driven by organic inputs and fertilizers, long-term effects of crop rotation may also interact with environmental drivers such as rainfall or freeze-thaw events. Laboratory results with intact soil cores from four rotations will be used to discuss the relative importance of carbon and nitrogen availability and soil gas diffusivity.
See more from this Division: ASA Section: Environmental Quality
See more from this Session: Symposium--Crop Influences On GHG Emissions and Soil C Sequestration