The effect of different fertilizer treatments on the invertebrate fauna on coniferous forest soil were investigated during the years 1979-83 both in field and in laboratory experiments. Fertilizers tested were urea (both alone and with P and K), ammonium nitrate and ashes. Ash-treatment was also controlled by raising the pH at the same level with Ca(OH)2.
Both ashes and urea resulted in considerable changes in the soil fauna. Nematodes, especially bacterial feeders, increased temporarily. Some families of Coleoptera invaded the urea-treated plots. Enchytraceid worms and several microarthropod species decreased, as well as the total animal biomass. Ash-treatment influenced more slowly than did urea-fertilizing, but it caused more permanent changes. Ammonium nitrate with lime had little influence in the field. All fertilizers affected more strongly when mixed with soil in laboratory. pH alone proved to explain most of the changes observed, but nitrogen as a nutrient also plays role independently of acidity.
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