Nitrous oxide emissions from fertilized and unfertilized soils in a subtropical region -Andalusia, Spain-

Field measurements of N2O emission rates were carried out from August until October 1982 in a subtropical region in Europe, i.e. in Andalusia, Spain. The measurements were performed by using an automatic sampling and analysis technique allowing the semi-continuous determination of N2O emission rates. The N2O emission rates were positively correlated to the soil surface temperature and exhibited a diurnal rhythm with maximum rates in the afternoon and minimum rates in the early morning with average values of 1 myg N2O-N/square meter/h for the grass lawn and 15 myg N2O-N/square meter/h for cultivated land. Application of urea and ammonium nitrate resulted in elevated N2O emission rates when compared to the unfertilized control. The loss of fertilizer-nitrogen as N2O was 0.18% for urea and 0.04% for NH4NO3 which compares very well with data obtained in a temperate climate (Germany). The total source strength of fertilizer-derived N2O is estimated to be 0.01-2.2 Tg N2O-N per year. The N2O flux from unfertilized natural soils may be as high as 4.5 Tg N2O-N, indicating that the N2O emission from soils contributes significantly to the global N2O budget. (IFU)