Regulations Of Soil Nitrification By Organic Matter

Nitrification is a crucial process in the terrestrial and aquatic nitrogen (N) cycle. It is essencial to study the factors regulating nitrification processes for promoting N use efficiency and reducing the influence of nitrification products such as NO₃^-, NO₂^- and nitrogen oxides on environments. Previous studies proved that NH₄⁺-N availability, the supply of O₂, temperature and pH are regulating factors of nitrification rate, but the regulating effects of organic matter remain unclear. In this thesis, two kinds of commercial organic fertilizers, dissolved organic matter (DOM) extracted from an organic fertilizer and two kinds of soil pollutants (aniline and phenol) were used to study their effect of amendment on nitrification. Results were as follows.Soil incubation results showed that nitrification activity increased with the increase of N levels. All of the treatments led to high amounts of NO₂^--N and NO₃^--N accumulations, which were enhanced by the increased N application level. However, the organic fertilizer with high C/N ratio (OF₁) significantly inhibited nitrification activity and reduced the NO₂^--N and NO₃^--N accumulations in comparison with other treatments, whereas the organic fertilizer with low C/N ratio (OF2) had little difference from ammonium sulfate in related to nitrification activity and accumulation of NCV-N and NCV-N. Dynamic monitoring results also showed that NCV-N accumulated in soil samples for more than two weeks under 300mg·kg^-1 N level. The study in this paper suggested that soil nitrification respond to amendment of organic fertilizers differently. More attentions should be paid on the risks of NCV-N and NCV-N entering into aquatic systems through soil leaching.Addition of DOM decreased nitrification rate to a certain extent, and the inhibiting effect increased with the increase of DOM addition. The addition of DOM increased NO₂^--N accumulation significantly and prolonged the formation of NP₃^--N. In order to eliminate the effect of nitrogen contained in DOM, we compared the effects of DOM addition and with (NH₄)₂SO₄ as sole nitrogen source on nitrification under the same original nitrogen concentration, the results also showed the increase of NP₂^--N...