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Continuous measurement of soil surface CO2, N2O and CH4 fluxes to estimate global warming potentials in Great Plains maize-based agroecosystems
CO2, N2O and CH4 are among the most important agriculturally generated trace gases involved in global climate change. Maize-based ecosystems are considered to have significant C sequestration potential associated with management practices. An automated closed chamber system was deployed in eastern Nebraska to make year-round measurements of soil surface CO2, N2O and CH4 fluxes in an irrigated maize (IM) (Zea mays L.) and a rainfed maize-soybean (RMS) (Glycine max (L.) Merr.) rotation systems. Soil surface fluxes of CO2, N2O and CH4 were investigated at diel, seasonal and annual time scales. Global warming potentials (GWP) were quantified for each system based on estimates of net ecosystem CO 2 exchange (NEE), production C-cost and soil surface N2O and CH4 fluxes. On a diel scale, maximum fluxes typically occurred in late afternoon. Seasonally, CO2 fluxes were relatively high during the growing season, and reached a maximum around silking stage of maize. Daily average CO2 flux for IM was significantly larger than RMS. N2O fluxes exhibited sharp peaks soon after fertilizer application following irrigation or precipitation at IM. Variability at RMS was less marked. CH4 fluxes were small in both systems. For RMS, CO2, N2O and CH4 fluxes at soybean phase were smaller than those at maize phase. Annual CO2 and CH4 emissions for IM were greater than those of RMS. The IM was a net source of greenhouse gas with an annual estimate of about 1100 g CO2-equivalents m-2, and about half of the net GWP was from N2O flux, and 30% from the site C balance. The RMS had a positive C mitigation potential of about 60 g CO 2-equivalents m-2 owing to a more favorable site C balance, and lower rates of N2O flux and production C-costs. The contribution of CH4 fluxes to GWP was small and negligible for both systems. Future agricultural management strategies should consider not only improving crop production but also reducing GWP. ^
Agriculture, Agronomy|Agriculture, Soil Science
Shen, Hui, "Continuous measurement of soil surface CO2, N2O and CH4 fluxes to estimate global warming potentials in Great Plains maize-based agroecosystems" (2008). ETD collection for University of Nebraska - Lincoln. AAI3316416.