Influence of soil properties on the turnover of nitric oxide and nitrous oxide by nitrification and denitrification at constant temperature and moisture

Soils are a major source of atmospheric NO and N2O. Since the soil properti es that regulate the production and consumption of NO and N2O are still lar gely unknown, we studied N trace gas turnover by nitrification and denitrif ication in 20 soils as a function of various soil variables. Since fertiliz er treatment, temperature and moisture are already known to affect N trace gas turnover, we avoided the masking effect of these soil variables by cond ucting the experiments in non-fertilized soils at constant temperature and moisture. In all soils nitrification was the dominant process of NO product ion, and in 50% of the soils nitrification was also the dominant process of N2O production. Factor analysis extracted three factors which together exp lained 71% of the variance and identified three different soil groups. Grou p I contained acidic soils, which showed only low rates of microbial respir ation and low contents of total and inorganic nitrogen. Group II mainly con tained acidic forest soils, which showed relatively high respiration rates and high contents of total N and NH4+ Group III mainly contained neutral ag ricultural soils with high potential rates of nitrification. The soils of g roup I produced the lowest amounts of NO and N2O. The results of linear mul tiple regression conducted separately for each soil group explained between 44-100% of the variance. The soil variables that regulated consumption of NO, total production of NO and N2O, and production of NO and N2O by either nitrification or denitrification differed among the different soil groups. The soil pH, the contents of NH4+ NO2- and NO3-, the texture, and the rates of microbial respiration and nitrification were among the important variab les.