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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 10, NUMBER 9, SEPTEMBER 1997

PROFESSIONAL PUBLICATIONS...
ANTHROPOGENIC EMISSIONS - AGRICULTURE

Item #d97sep28

"N₂O Emissions from Energy Crop Fields of Miscanthus 'Giganteus' and Winer Rye," R.N. Jorgensen (Plant Nutrition Lab., Roy. Veterinary & Agric. Univ., Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark), B.J. Jorgensen et al., Atmos. Environ., 31(18), 2599-2904, Sep. 1997.

N₂O emissions from fields of energy crops diminish their greenhouse gas advantage over fossil fuels. Measurements with and without fertilizer addition suggest that this is a minor effect for the studied species grown in sandy loam.

Item #d97sep29

"Methane Emissions Measured Directly from Grazing Livestock in New Zealand," K.R. Lassey (Natl. Inst. of Water & Atmos. Res., POB 14-901, Kilbirnie, Wellington, New Zealand), M.J. Ulyatt et al.,Atmos. Environ., 31(18), 2905-2914, Sep. 1997.

Reports the first measurements of methane emissions from grazing sheep, and among the first from grazing cattle. Daily emissions from sheep varied by a factor of 1.4 and were unrelated to variations in intake, a factor that could influence strategies to control emissions.

Item #d97sep30

"CH₄ and N₂O Fluxes in the Colorado Shortgrass Steppe. 2. Long-Term Impact of Land Use Change," A.R. Mosier (Agric. Res. Serv., USDA, POB E, Ft. Collins CO 80522; e-mail: amosier@lamar.colostate.edu), W.J. Parton et al., Global Biogeochem. Cycles, 11(1), 29-42, Mar. 1997.

Provides needed data on the short-term and long-term effects on emissions of cultivating native grasslands. Conversion of grasslands to croplands typically decreased the soil consumption of atmospheric methane and increased N₂O emissions; these changes were still significant after three years or more.

Item #d97sep31

"Influence of Cattle Wastes on Nitrous Oxide and Methane Fluxes in Pasture Land," H. Flessa (GSF-Inst. fur Bodenökologie, Neuherbert, POB 1129, D-85764 Oberschleissheim, Ger; e-mail: hflessa@ufbwserver.uni-forst.gwdg.de), P. Dörsch, et al.,J. Environ. Qual., 25(6), 1366-1370, Nov.-Dec. 1966.

Measured emissions from dung patches, which are hot spots of methane production, and urine-affected areas, which show high N₂O release. Methane emissions are small compared to those from the rumen of the cattle, but droppings from large ruminants may be an important and drastically underestimated source of atmospheric nitrous oxide.

Item #d97sep32

"Estimates of Global N₂O Emissions from Cattle, Pig and Chicken Manure, Including a Discussion of CH₄ Emissions," M.G.M. Berges (Div. Atmos. Chem., Max Planck Inst. Chemie, POB 3060, 55020 Mainz, Ger.), P.J. Crutzen, J. Atmos. Chem., 24(3), 241-269, July 1996.

Derives estimates by measuring the molar emission ratio of N₂O to NH3, considered to be the parameter giving the most stable numerical basis for regional and global extrapolation. Measurements of this ratio made for various types of animal bedding and manure treatment showed wide variation, and further research is needed to refine global emission estimates and devise control strategies. However, results indicate that animal manure may well be a major anthropogenic source of N₂O.

Item #d97sep33

"Model Estimates of Nitrous Oxide Emissions from Agricultural Lands in the United States," C. Li (Inst. for Study of Earth, Oceans & Space, Univ. New Hampshire, Durham NH 03824), V. Narayanan, R.C. Harriss,Global Biogeochem. Cycles, 10(2), 297-306, June 1996.

Uses the Denitrification-Decomposition model to elucidate the influence of climate, soil properties and farming practices on spatial and temporal variations in agricultural emissions of N₂O. Soil tillage and fertilizer use were the most important factors contributing to emissions at the national scale; nitrate pollution in rainfall may also be a significant anthropogenic factor. Results suggest that the U.S. government and possibly the IPCC have underestimated the importance of agriculture as a source of N₂O, and the highly coupled nature of the nitrogen and carbon cycles in soils complicates the formulation of strategies to reduce emissions.