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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGICALLY-SOUND PEST, WATER AND SOIL MANAGEMENT STRATEGIES FOR NORTHERN GREAT PLAINS CROPPING SYSTEMS Title: Net greenhouse gas emissions affected by sheep grazing under dryland cropping systems

Authors
item Barsotti, Joy
item Sainju, Upendra
item Lenssen, Andrew
item Montagne, Cliff -
item Hatfield, Patrick -

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 19, 2013
Publication Date: May 19, 2013
Repository URL: http://handle.nal.usda.gov/10113/56714
Citation: Barsotti, J.L., Sainju, U.M., Lenssen, A.W., Montagne, C., Hatfield, P.G. 2013. Net greenhouse gas emissions affected by sheep grazing under dryland cropping systems. Soil Science Society of America Journal. 77:1012-1025.

Interpretive Summary: Sheep grazing during fallow periods or after grain harvest is often used to control weeds and pests, reduce feed cost, and increase nutrient cycling under dryland farming in the northern Great Plains. Sheep grazing may influence greenhouse gas (GHG) emissions by consuming crop residue and returning feces and urine to the soil. Little is known about the effect of sheep grazing on GHG emissions under dryland cropping systems in the northern Great Plains. The effect of sheep grazing compared to herbicide application for weed control was evaluated on soil temperature and water content at the 0- to 15-cm depth and GHG emissions in a silt loam from May to October, 2010 and 2011 under dryland cropping systems in western Montana. Treatments were two fallow management practices (sheep grazing [GRAZ] and herbicide application [CHEM]]) and three cropping sequences (continuous alfalfa [CA], continuous spring wheat [CSW], and spring wheat-pea/barley hay-fallow [W-P/B-F]). Gas samples were collected at 3 to 14 d intervals with a vented, static chamber. Soil temperature and water content were greater in CHEM with W-P/B-F than in other treatments. Regardless of treatments, GHG fluxes peaked immediately following substantial precipitation (>12 mm) and/or N fertilization mostly from May to August. Total CO2 flux from May to October was greater in GRAZ with CA but total N2O flux was greater in CHEM and GRAZ with CSW than in other treatments. Total CH4 flux was greater in CA than in W-P/B-F. Accumulation of sheep feces and urine, followed by greater root respiration probably increased CO2 emissions in grazing under alfalfa but greater N rate increased N2O emissions and a variable effect on CH4 emissions under spring wheat. For accounting global warming potential, additional information on soil C dynamics and CO2 emissions associated with production inputs, sheep enteric fermentation, and machinery use are needed.

Technical Abstract: Sheep grazing to control weeds during fallow may influence greenhouse gas (GHG) emissions by consuming crop residue and returning feces and urine to the soil. We evaluated the effect of sheep grazing compared to herbicide application for weed control on soil temperature and water content at the 0- to 15-cm depth and GHG emissions in a silt loam from May to October, 2010 and 2011 under dryland cropping systems in western Montana. Treatments were two fallow management practices (sheep grazing [GRAZ] and herbicide application [CHEM]]) and three cropping sequences (continuous alfalfa [CA], continuous spring wheat [CSW], and spring wheat-pea/barley hay-fallow [W-P/B-F]). Gas samples were collected at 3 to 14 d intervals with a vented, static chamber. Soil temperature and water content were greater in CHEM with W-P/B-F than in other treatments. Regardless of treatments, GHG fluxes peaked immediately following substantial precipitation (>12 mm) and/or N fertilization mostly from May to August. Total CO2 flux from May to October was greater in GRAZ with CA but total N2O flux was greater in CHEM and GRAZ with CSW than in other treatments. Total CH4 flux was greater in CA than in W-P/B-F. Accumulation of sheep feces and urine, followed by greater root respiration probably increased CO2 emissions in grazing under alfalfa but greater N rate increased N2O emissions and a variable effect on CH4 emissions under spring wheat. For accounting global warming potential, additional information on soil C dynamics and CO2 emissions associated with production inputs, sheep enteric fermentation, and machinery use are needed.

Last Modified: 12/18/2014
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