Effects of fertilisation on soil microbes

Abstract

Forest fertilisation influences mineralisation and thus the release of nutrients from the organic matter in the soil. Fast-release nitrogen fertilisers, e.g. urea and ammonium nitrate, bring about a long-term reduction in carbon mineralisation (CO₂ production) (Söderström et al. 1983, Martikainen et al. 1989, Nohrstedt et al. 1989, Aarnio and Martikainen 1994), especially on relatively nutrient-poor forest sites (Martikainen et al. 1989, Arnebrant et al. 1996). The reasons for the long-term reduction in microbial activity resulting from a nitrogen input are not known. It has been suggested that nitrogen addition causes changes in the production of exoenzymes (Keyser et al. 1978) or ion concentrations in the soil, and the pH conditions of the environment become unfavourable for microbes (Fog 1988, Martikainen 1996).