High fluxes but different patterns of nitrous oxide and carbon dioxide emissions from soil in a cattle overwintering area

Cattle overwintering areas common in central Europe may represent significant point sources of the important greenhouse gases, nitrous oxide (N2O) and carbon dioxide (CO2). A 2-year field study was carried out in order to estimate the emissions of N2O and CO, from soil in a cattle overwintering area located in the southwest of the Czech Republic. The measurements were performed at three sampling locations along a gradient of animal impact (severe, moderate, slight) to test the hypothesis that emissions of CO, and NO are positively related to the degree of impact. In addition to CO2 and N2O fluxes determined by using non-vented manual closed chambers, soil mineral nitrogen (NH4+ and NO3-), pH and temperature were determined to assess their regulatory role and impact on gas fluxes. The overwintering area was about 4 ha and it had been used for overwintering of about 90 cows since 1995. Deposition of animal excreta resulted in a significant accumulation of nitrogen in the soil during winter, but most of the N2O was emitted during a few short periods in spring and/or in late autumn. Maximum N2O fluxes of up to 2.5 mg N2O-N m(-2) h(-1) were recorded at the most impacted location near the animal house, where the highest concentrations of soil mineral nitrogen also occurred. The emissions Of CO2 showed a completely different pattern to those of N2O, being correlated with soil temperature; the highest emissions thus occurred in June-July, while very low fluxes were found in winter. Emission values ranged from about 0 to 700 mg C-CO2 m(-2) h(-1). Furthermore, the effect of animal impact on CO2 emissions was opposite to that on N2O fluxes, as the highest CO2 fluxes were mostly recorded at the least impacted location, where respiration of plants most likely increased overall CO, production. The results show that cattle overwintering areas are important sources of greenhouse gases, including N2O and CO2. Fluxes of these two gases are, however, differently distributed over the year, which also suggests that they are controlled by different environmental and soil factors. (c) 2006 Elsevier B.V. All rights reserved.