Organic nitrogen mineralization in temperate humid-zone soils after two and six weeks of aerobic incubation

摘要

The N mineralization rate in 11 soils was studied by aerobic incubation at 28°C and at a moisture content of 75 of field capacity for 2 weeks (short term) and 6 weeks (medium term). Relationships between the N mineralization indices for each period were evaluated. Ammonification largely predominated during the first 2 weeks of incubation, whereas nitrification was the predominant process between weeks 2 and 6. The net N mineralized in the different soils varied from 0 to 2.85 of the organic N after 2 weeks of incubation and from 0.32 to 3.36 of the organic N after 6 weeks of incubation, the mean values for each period being 0.82 and 1.51 of the organic N, respectively. The quantities of NHinf4sup+-N, NOinf3sup--N, and total inorganic N produced and the percentage of organic N mineralized after 2 weeks of incubation were highly and positively correlated with the coresponding values after 6 weeks of incubation. These results showed that either length of incubation could be used to determine the potential N mineralization capacity of the soils. Information obtained from two incubation periods was largely supplementary for the kinetic study of N mineralization, ammonification, and nitrification; therefore a medium-term incubation with intermediate measurements of N mineralization over a short term may be more useful than a single measurement using either of the two incubation periods