NITROUS-OXIDE EMISSION FROM AN AGRICULTURAL SOIL SUBJECTED TO DIFFERENT FREEZE-THAW CYCLES

Nitrous oxide (N2O) emissions from soils have been implicated as the causes of potential greenhouse warming and important nitrogen (N) loss. Soil freeze-thaw cycles have a significant effect on N2O emission. In this study, potential rates of N2O emission from an agricultural soil were examined in the laboratory by a soil core method. Spring soil cores from a sandy loam under conventional tillage and inorganic fertilizer management practices were distributed to four different freeze-thaw treatment groups. One group of the soil cores was not refrozen during the experiment, with the others subjected to one, two and three freeze-thaw cycles, respectively. The N2O flux from the soil core increased with increasing numbers of freeze-thaw cycles. The means of the fluxes ranged from 0.24 to 0.65 kg ha(-1) day(-1) for non-frozen soil cores and about 60% higher value were found for one freeze-thaw cycle treatment. The results also showed that the first freeze-thaw cycle promoted N2O flux as a pulse and the same patterns were found for additional freeze-thaw cycles. The information in this study should allow estimation of the potential rates of N2O emission contributed by freeze-thaw events for specific locations based on the soil climate data for the location.