The present paper aimed at a definition of the pore cross-sections elongation index in soil lessivé (0–8 cm layer) under onion field after different cultivation treatments and in changeable weather conditions. The measurements were taken using binary images of opaque soil blocks surfaces sized 75.0 mm × 65.0 mm. Considering difficulty in shape classification of smaller pores for the shape analysis the pores sections with the surfaces of at least 100 pix2 were chosen, which corresponds to 0.179 mm2. The following groups of pore cross-sections were defined according to elongation index: circular 0–0.1, elliptical 0.11–0.5 and elongated > 0.51. It was stated that elongated pores dominated in each tested state of soil, regardless of differentiation of external factors. Circular pores had a little percentage in total numbers of pores. The lowest values of numbers of all pores were observed in soil samples after passage of tractor during fertilization and a month after tractor pressure and onion removal.