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Title: Impacts of Cropping Intensity on Soil C and Net Greenhouse Gas Fluxes for Dryland Cropping in Northeastern Colorado

Author
item Del Grosso, Stephen - Steve
item Sherrod, Lucretia
item MOSIER, ARVIN - U OF FL, GAINESVILLE, FL
item PETERSON, G - CO ST U, FT. COLLINS, CO
item Ahuja, Lajpat
item HANSEN, N - CO ST U, FT. COLLINS, CO

Submitted to: Proceedings Great Plains Soil Fertility Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/4/2008
Publication Date: 3/4/2008
Citation: Del Grosso, S.J., Sherrod, L.A., Mosier, A., Peterson, G.A., Ahuja, L.R., Hansen, N. 2008. Impacts of Cropping Intensity on Soil C and Net Greenhouse Gas Fluxes for Dryland Cropping in Northeastern Colorado. Proceedings Great Plains Soil Fertility Conference. Vol. 12, pp. 40-44.

Interpretive Summary: Winter wheat/summer fallow cropping has been, and remains, a common cropping system in semi-arid regions of the US Great Plains. The fallow (plant free) period conserves water and minimizes the probability of catastrophic crop failure but low residue inputs and conventional tillage lead to losses of soil organic carbon and carbon dioxide emissions to the atmosphere. In recent years, reduced tillage and cropping intensification (i.e., reduced summer fallow) have been adopted by some farmers and these practices have led to carbon gains in some soils. In 1985, land that was traditionally used for conventional tillage wheat/fallow cropping was converted to no till alternative cropping systems to investigate soil carbon changes. After 12 years of average to above average precipitation, continuous no till cropping with out summer fallow had stored more than twice the amount of carbon in soil compared to no till wheat/corn/fallow cropping. However most of the carbon stored under summer cropping was lost during the next 6 years, primarily due to 3 crop failures associated with drought beginning in 1999. The summer cropping system had almost 10 times the net greenhouse gas emissions as the wheat/corn/fallow system over the 18 year period of the experiment. Interactions between cropping system and weather have profound impacts on soil carbon storage and total greenhouse gas emissions.

Technical Abstract: In 1985, land that was traditionally used for conventional tillage wheat/fallow cropping was converted to no till alternative cropping systems to investigate soil carbon changes. After 12 years of average to above average precipitation, continuous no till cropping with out summer fallow had stored more than twice the amount of carbon in soil compared to no till wheat/corn/fallow cropping. However, after 18 years, the wheat/corn/fallow system had stored almost 3 times as much carbon in soil as the continuous cropping, primarily due to decreased biomass inputs for the continuous summer cropping system with 3 crop failures associated with drought beginning in 1999. The continuous cropping system had almost 10 times the net greenhouse gas emissions as the wheat/corn/fallow system over an 18 year period which included 6 years of drought. Net greenhouse gas flux included CO2 emissions from manufacture and transport of fertilizer and farm operations, soil organic C changes, and the CO2 equivalents of N2O emissions and CH4 fluxes. During prolonged drought periods, cropping system rotation as well as the choice of crop within a system can have profound impacts on soil carbon storage and greenhouse gas emissions.