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 N(2)O. Since the soil properties that regulate the production and consumption of NO and N(2)O are still largely unknown, we studied N trace gas turnover by nitrification and denitrification in 20 soils as a function of various soil variables. Since fertilizer treatment, temperature and moisture are already known to affect N trace gas turnover, we avoided the masking effect of these soil variables by conducting the experiments in non-fertilized soils at constant temperature and moisture. In all soils nitrification was the dominant process of NO production, and in 50% of the soils nitrification was also the dominant process of N(2)O production. Factor analysis extracted three factors which together explained 71% of the variance and identified three different soil groups. Group I contained acidic soils, which showed only low rates of microbial respiration and low contents of total and inorganic nitrogen. Group II mainly contained acidic forest soils, which showed relatively high respiration rates and high contents of total N and NH(4)(+) Group III mainly contained neutral agricultural soils with high potential rates of nitrification. The soils of group I produced the lowest amounts of NO and N(2)O. The results of linear multiple 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 N(2)O, and production of NO and N(2)O by either nitrification or denitrification differed among the different soil groups. The soil pH, the contents of NH(4)(+) NO(2)(-) and NO(3)(-), the texture, and the rates of microbial respiration and nitrification were among the important variables.