ABSTRACT Spatial variation of soil carbon dioxide (CO2) flux during a growing season within corn and soybean canopies has not been quantified. These cropping systems are the most intense in the United States and the potential for carbon (C) sequestration in these systems through changes in soil management practices create an opportunity for reduction in greenhouse gas emissions; however, the need to understand the variation in fields is critical to evaluating changes in management systems. A study was designed to evaluate the spatial variation in soil CO2 fluxes along two transects in corn and soybean fields. Samples were collected every 5 m along a 100 m transect between the rows of the crop and also along a transect in which the plants had been removed to reduce the potential of root respiration. Soil CO2 fluxes were collected at each position with air temperature, soil temperature at 0.05 m, and soil water content (0 - 0.06 m). At the end of the season, soil samples for the upper 0.1 m were collected for soil organic C content, pH, sand, silt, and clay contents. On each day measurements were made, the observed CO2 emissions were scaled by dividing the CO2 flux at each position by the mean CO2 flux of the entire transect. Observed CO2 fluxes were signifycantly larger in the row than in the fallow position for both crops. There were no differences between the corn and soybean fallow transects; however, the corn row samples were larger than the soybean row samples. No consistent spatial patterns were observed in the CO2 fluxes or any of the soil properties over the course of the study. When the CO2 flux data were combined over the season, there was a significant spatial pattern in the fallow transects for both crops but not for the row transects. Sampling for CO2 flux
values in cropping systems has to consider the presence of a crop canopy and the amount of root respiration.
Cite this paper
Hatfield, J. and Parkin, T. (2012) Spatial variation of carbon dioxide fluxes in corn and soybean fields. Agricultural Sciences, 3, 986-995. doi: 10.4236/as.2012.38120.
 West, T.O. and Marland, G.A. (2002) Synthesis of carbon sequestration, carbon emissions and net carbon flux in agriculture: comparing tillage practices in the United States. Agriculture, Ecosystems and Environment, 91, 217- 232. doi:10.1016/S0167-8809(01)00233-X
 Parkin, T.B., Kaspar, T.C., Senwo, Z., Prueger, J.H. and Hatfield, J.L. (2005) Relationship of soil respiration to crop and landscape in the Walnut Creek watershed. Journal of Hydrometeorology, 6, 812-824.
 Buyanovsky, G.A., Kucera, C.L. and Wagner, G.H. (1985) Comparative carbon balance in natural and agricultural ecosystems. Bulletin of the Ecological Society of America, 66, 149-150.
 Baldocchi, D., et al. (2001) Fluxnet: A new tool to study the temporal and spatial variability of ecosystem scale carbon dioxide, water vapor and energy flux densities. Bull. American Meteorological Society, 82, 2415-2434.
 Morell, F.J., Alvaro-Fuentes, J., Lampurlanes, J. and Cantero-Martinez, C. (2010) Soil CO2 fluxes following tillage and rainfall events in a semiarid Mediterranean agroecosystem: Effects of tillage systems and nitrogen fertilization. Agriculture, Ecosystems and Environment, 139, 167-173. doi:10.1016/j.agee.2010.07.015
 La Scala Jr., N., Lopes, A., Spokas, K., Bolonhezi, D., Archer, D.W. and Reicosky, D.C. (2008) Short-term temporal changes of soil carbon losses after tillage described by a first-order decay model. Soil and Tillage Research, 99, 108-118. doi:10.1016/j.still.2008.01.006
 Khomik, M., Altaf Arain, M., and McCaughey, J.H. (2006) Temporal and spatial variability of soil respiration in a boreal mixed wood forest. Agricultural and Forest Meteorology, 140, 244-256.
 Itoh, M., Kosugi, Y., Takanashi, S., Hayashi, Y., Kanemitsu, S., Osaka, K., Tani, M. and Nik. A.R. (2010) Temporal and spatial variations of soil carbon dioxide, methane, and nitrous oxide fluxes in a Southeast Asian tropical rainforest. Biogeosciences, 7, 6847-6887.
 Maestre, F.T. and Cortina, J. (2003) Small scale spatial variation in soil CO2 flux in a Mediterranean semiarid steppe. Applied Soil Ecology, 23, 199-209.
 Lee, J., Hopmans, J.W., van Kessel, C., King, A.P., Evatt, K.J., Louie, D., Rolston, D.E. and Six, J. (2009) Tillage and seasonal emissions of CO2, N2O and NO across a seed bed and at the field scale in a Mediterranean climate. Agriculture, Ecosystem and Environment, 129, 378-390.
 Hatfield, J.L., Jaynes, D.B., Burkart, M.R., Cambardella, C.A., Moorman, T.B., Prueger, J.H. and Smith, M.A. (1999) Water quality in Walnut Creek watershed: Setting and farming practices. Journal of Environmental Quality, 28, 11-24. doi:10.2134/jeq1999.00472425002800010002x
 Nelson, D.W. and Sommers, L.E. (1996) Total carbon, organic carbon, and organic matter. In Sparks, D.L., et al., Eds., Methods of Soil Analysis. Part 3, SSSA Book Series, Madison, 961-1010.
 Matthias, A.D., Blackmer, A.M. and Bremner, J.M. (1980) A simple chamber technique for field measurement of emission of nitrous oxide from soil. Journal of Environmental Quality, 9, 251-256.
 Hutchinson, G.L. and Mosier, A.R. (1981) Improved soil cover method for field measurement of nitrous oxide fluxes. Soil Science Society of America Journal, 45, 311- 316. doi:10.2136/sssaj1981.03615995004500020017x
 Parkin, T.B., Doran, J.W. and Franco-Vizcaino, E. (1996) Field and laboratory tests of soil respiration. In: Doran, J.W. and Jones, A.J. Eds., Methods for Assessing Soil Quality, SSSA Special Publication, Madison, 231-245.
 Cambardella, C.A., Moorman, T.B., Novak, J.M., Parkin, T.B. and Karlen, D.L. (1994) Field-scale variability of soil properties in central Iowa soils. Soil Science Society of America Journal, 58, 1501-1511.
 Yates, T.T., Si, B.C., Farrell, R.E. and Pennock, D.J. (2006) Probability distribution and spatial dependence of nitrous oxide emission: Temporal change in hummocky terrain. Soil Science Society of America Journal, 70, 753-762.
 Rochette, P. and Flanagan, L.B. (1997) Quantifying rhizosphere respiration in a corn crop under field conditions. Soil Science Society of America Journal, 61, 466-474.
 Rochette, P., Flanagan, L.B. and Gregorich, F.B. (1999) Separating soil respiration into plant and soil components using analyses of the natural abundance of carbon-13. Soil Science Society of America Journal, 63, 1207-1213.
 Prueger, J.H., Hatfield, J.L., Parkin, T.B., Kustas, W.P. and Kaspar, T.C. (2004) Carbon dioxide dynamics during a growing season in Midwestern cropping systems. Environmental Management, 33, 330-343.