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Fluxes of carbon dioxide, nitrous oxide, and methane in grass sod and winter wheat-fallow tillage management

Kessavalou, A., Mosier, A.R., Doran, J.W., Drijber, R.A., Lyon, D.J., Heinemeyer, O.
Journal of environmental quality 1998 v.27 no.5 pp. 1094
greenhouse gases, elevated atmospheric gases, gas emissions, carbon dioxide, nitrous oxide, methane, winter wheat, fallow, cropping systems, tillage, Triticum aestivum, sod strips, soil pore water, soil temperature, spring, summer, autumn, winter, carbon sequestration, seasonal variation, temporal variation, no-tillage, plowing, soil organic carbon, Nebraska
Cropping and tillage management can increase atmospheric CO2, N2O, and CH4 concentrations, and contribute to global warming and destruction of the ozone layer. Fluxes of these gases in vented surface chambers, and water-filled pore space (WFPS) and temperature of survace soil were measured weekly from a long-term winter wheat (Triticum aestivum L.)-fallow rotation system under chemical (no-tillage) and mechanical tillage (noninversion subtillage at 7 to 10 cm or moldboard plowing to 15 cm) follow management and compared with those from "native" grass sod at Sidney, NE, from March 1993 to July 1995. Cropping, tillage, within-field location, time of year, soil temperature, and WFPS influenced net greenhouse gas fluxes. Mean annual interrow CO2 emissions from wheat-fallow ranged from 6.9 to 20.1 kg C ha-1 d-1 and generally increased with intensity and degree of tillage (no-till least and plow greatest). Nitrous oxide flux averaged <1.2 g N ha-1 d-1 for sod and 1 to 2 g N ha-1 d-1 for wheat-fallow. Tillage during fallow increased N2O flux by almost 100%. Nitrous oxide emissions were 1.5 to 3.7 times greater from crop row than interrow locations with greatest differences occurring during periods of highest N2O emission. Mean annual N2O flux over the 3 yr of study were 1.54 and 0.76 g N ha-1 d-1 for row and interrow locations. Methane uptake ranged from 5.9 to 9.9 g C ha-1 d-1 and was not influenced by row location. Seasonal CO2 and N2O flux, and CH4 uptake ranked as spring greater than or equal to summer > autumn > winter. Winter periods accounted for 4 to 10% and 3 to 47% of the annual CO2 and N2O flux, respectively, and 12 to 21% of the annual CH4 uptake. Fluxes of CO2 and N2O, and CH4 uptake increased linearly with soil temperature. No-till fallow exhibited the least threat to deterioration of atmospheric or soil quality as reflected by greater CH4 uptake, decreased N2O and CO2 emissions, and less loss of soil organic C than tilled soils. However, potential for increased C sequestration in this wheat-fallow system is limited due to reduced C input from intermittent cropping.