The aim of the study was to determine whether long-term intensive cultivation that used variable ploughing and fertilisation technologies and schemes influences the differentiation of soil properties which may impact the results of growing experiments in a relatively small experimental field (0.1 ha). The field under study is located in Wrocław, in an agricultural experimental station that has been operating for more than 60 years. A transformation of rusty gleyic soils (Brunic Gleyic Arenosols) into anthropogenic black earths (Gleyic Phaeozems (Arenic)) was noticed. The content of organic carbon and nitrogen, pH and the content of exchangeable base cations in the plough layer were positively (statistically and spatially) correlated and their increased values were observed in soils with a deeper and darker plough level. The present differentiation of the physical and chemical properties of soils in the experimental field do not result from such primary soil-forming factors as a kind and texture of parent material, topography, moisture regime, or (micro-)climatic conditions, which are not differentiated within the field, but from various intensity of former cultivation on individual sections of the experimental field. The variability cśfficient of the crucial soil properties was found to exceed 30%, which might significantly influence the results of micro-plot vegetation experiments.