The development and maintenance of the structure of humus soil horizons are predominantly influenced by roots and soil fauna, among which earthworms are considered the most important structural engineers in soils of temperate regions. The aim of this paper was to study changes in aggregation in an upland grassland soil following the application of mineral fertilizers and farmyard manure, and to compare excremental pedofeatures in the soil under different fertilization systems. In the studied upland grassland soil a subangular blocky structure was formed, the best developed, with many channels in manured soil, and the weakest in NPK-treated soil. The addition of fertilizers influenced the share of aggregates of fauna origin in studied treatments: FYM application increased the presence of aggregates while mineral fertilization decreased it in comparison with untreated soil. FYM-fertilized soil was characterized by a large presence of macroaggregates, while in NPK soil small aggregates prevailed.