SOIL CARBON AND CLIMATE CHANGE NEWS
From Kansas State University's:
Consortium for Agricultural Soils Mitigation of Greenhouse Gases (CASMGS)
http://soilcarboncenter.k-state.edu
Charles W. Rice, K-State Department of Agronomy, National CASMGS Director
(785) 532-7217 cwrice@ksu.edu
Scott Staggenborg, K-State Department of Agronomy (785) 532-7214 sstaggen@ksu.edu
Steve Watson, CASMGS Communications (785) 532-7105 swatson@ksu.edu
September 8, 2010
No. 79
Grazing Management Contributions to
Net Global Warming Potential
A study was undertaken to determine the net global warming potential (GWP) of three grazing management systems located within the northern Great Plains. Grazing management systems included two native vegetation pastures (moderately grazed and heavily grazed) and a heavily grazed crested wheatgrass pasture near Mandan, ND. Factors evaluated for their contribution to GWP included (i) CO2 emissions associated with N fertilizer production and application, (ii) literature-derived estimates of CH4 production for enteric fermentation, (iii) change in soil organic carbon (SOC) over 44 years using archived soil samples, and (iv) soil–atmosphere N2O and CH4 fluxes over 3 years using static chamber methodology.
Analysis of SOC indicated all pastures to be significant sinks for SOC, with sequestration rates ranging from 0.39 to 0.46 Mg C per hectare per year. All pastures were minor sinks for CH4. Greater N inputs within on the crested wheatgrass pasture contributed to annual N2O emission nearly threefold greater than either of the native grass pastures. Due to differences in stocking rate, CH4 production from enteric fermentation was nearly threefold less in the moderately grazed native pasture than either the crested wheatgrass or heavily grazed native pastures.
When factors contributing to net GWP were summed, the heavily and moderately grazed native pastures were found to serve as net CO2 equivalent sinks, while the crested wheatgrass pasture CWP was a net CO2 equivalent source. Values for GWP and GHG intensity, however, indicated net reductions in GHG emissions can be most effectively achieved through moderate stocking rates on native vegetation.
The researchers were M.A. Leibig, J.R. Gross, S.L. Kronberg, and R.L. Phillips, USDA-ARS Northern Great Plains Research Lab, Mandan, ND.
Source: Journal of Environmental Quality, doi: 10.2134/jeq2009.0272Vol. 39 No. 3, p. 799-809
https://www.agronomy.org/publications/jeq/abstracts/39/3/799