Submitted to: USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry
Publication Type: Abstract Only
Publication Acceptance Date: 2/5/2007
Publication Date: 2/7/2007
Citation: Dell, C.J., Skinner, R.H., Adler, P.R., Schmidt, J.P. 2007. Nitrous Oxide and Methane Emissions from Grazed Pasture [abstract]. USDA Symposium on Greenhouse Gases & Carbon Sequestration in Agriculture and Forestry. p.1 Interpretive Summary: An interpretive summary is not required.
Technical Abstract: The contribution of nitrous oxide and methane to the atmosphere from grazed pastures in the eastern U.S. is not well known. Small, vented chambers have been deployed periodically since May 2005 in a rotationally-grazed pasture in central Pennsylvania. Since locations in pastures where livestock urine and dung are deposited are believed to contribute greatly to emissions from pasture, those sources were measured separately from locations with no evidence of fresh waste deposition. Nitrous oxide emissions are greatly influenced by soil moisture. When soil is dry to moderately moist, mean nitrous oxide emissions from locations that have not received waste are generally less than 10 g N/ha/d. However, mean emissions as high as 200 g nitrous oxide-N/ha/d have been observed after large rainfall events. Elevated nitrous oxide emissions were consistently observed from sampling points at dung piles and urine spots within 10 days after grazing with peak emission rates up to approximately 1000 and 500 g nitrous oxide N/ ha/d from urine patches and dung piles, respectively. Soil moisture also greatly influenced the amount and duration of emissions from dung piles and urine patches. On average, we estimate that emissions in response to fresh waste inputs contribute 10 to 20% of the total nitrous oxide emission from the pasture. Methane emissions were observed only from freshly deposited dung and diminished quickly as dung dried. Soils without fresh dung deposits were a small sink for methane, and the size of that sink was comparable to the quantity of methane emitted from dung. Given the complex interaction between nitrous oxide emission rates and soil moisture and the influence of other factors (such as soil temperature, fertilizer addition, stocking rates, and plant species composition), a modeling approach is likely needed to estimate emission from intensively grazed systems.