Course of cellulose decomposition in a brown earth under a Trisetum flavescens – meadow after different fertilization The cellulose decomposition in the soil of a Trisetum flavescens‐meadow untreated and treated with NPK. and PK fertilizer was determined by means of burial of pieces of cellophane. The rate of decomposition of the cellulose film was chosen as a measure of cellulolytic activity in soil. The cellulolytic activity had its maximum in the summer months and near the surface. The decrease with increasing depth was more obvious in the untreated lot than in the lot treated with NPK fertilizer. Under field conditions the influence of fertilization on the cellulolytic activity was low. In the laboratory there was a slight effect of the addition of soil from the NPK‐lot on the decomposition of filter paper only with a slightly alkaline nutritive solution. The determination of soil cellulose content and mineralization of soil cellulose showed no differences between fertilized and untreated soil.