Nitrous Oxide Emissions from Agricultural Soils in Wisconsin
1984
Goodroad, L. L. | Keeney, D. R. | Peterson, Laurence A.
Nitrous oxide (N₂O) emissions from field plots on a Plano silt loam soil (Typic Argiudolls) at the University of Wisconsin-Arlington Experimental Farm were measured from the summer of 1979 through autumn 1981. The treatments, selected to give a wide variation in management, were: reduced tillage (till-plant) corn (Zea mays L.); rye (Secale sativa L.) cover; long-term stable pH (pH 4.7, 5.1, and 6.7); oat (Avena sativa L.) straw residue; alfalfa (Medicago sativa L.) residue; and dairy manure and sewage sludge amendments. Nitrous oxide fluxes, measured by a static chamber technique, were greatest with the manure-amended and reduced tillage treatments, and were greater in 1980 than in 1979 or 1981. Highest rates of N₂O emission were often observed at soil thaw. No significant effects on the emission rate or amount of N₂O evolved due to soil pH was observed. Surface N₂O fluxes were characterized by a high degree of variation. Mean N₂O-N emission rates calculated from measured N₂O-N emission rates during annual sampling periods ranged from 1.6 to 38.7 ng N₂O-N m⁻² s⁻¹ for the treatments sampled. Coefficients of variation for these means ranged from 50% to > 200% and from 100 to 350% for spatial and temporal variability, respectively. Total N₂O emissions (kg N₂O-N ha⁻¹) for 1980, the most complete sampling period, were: reduced tillage corn, 3.5 in the row and 6.3 between the row; sludge, 1.6; manure, 6.1; alfalfa, 3.2; rye, 1.6; straw, 2.2; pH 4.7, 1.5; pH 5.1, 0.9; pH 6.7, 1.0. These values are similar to those reported in the literature from comparable agricultural sites.
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