Abstract Weediness of crops of field crops is examined in various crop rotations. Different types of weeds have unequal effects on crop plants. An expression of this effect is the harmfulness of weeds, which leads to a decrease in yield and a deterioration in the quality of the products. It is possible to change the species composition of weeds in the course of time on agricultural crops, which depends on the intensity of the cultivation technology and, first of all, on the alternation of crops and the introduction of straw. Monitoring of weed infestation of crops is necessary to predict the spread of the most harmful weeds in crop rotations. The aim of the research is to trace the dynamics of weediness and species composition of weeds on sodpodzolic soil in field crop rotations. The research was carried out in 1998-2017 on a stationary site, on sod-podzolic medium loamy soil with a high content of mobile forms of phosphorus and exchangeable potassium. The biomorphological spectrum of weed species indicates that 26 species of juvenile weeds occur, and 9 species of perennial species. The appearance of Chenopodium album L. was the most common. There is an increase in the abundance of weeds during the research in the studied agrocenoses. If 61 specimens of weed vegetation per 1 m2 were observed in the first rotation, including 50 annual ones, then in the second rotation the abundance of weeds increased to 67 pieces / m2. The greatest amount of weed vegetation was observed - 76 pieces/m2 in the third rotation of crop rotations. We come to the conclusion that the weediness of field agrocenoses increases, examining the dynamics of the contamination of crop field crop rotations, especially over the last six years of research. The number of species of Fumaria officinalis L. and Stellaria media (L.) Vill increases during the study. The number of species of Chenopodium album L. and Echinochloa crus-galli L. has increased significantly over the past six years. We found that the crops in the first crop rotation were the most littered. The rotation, including grasses and row crops, helps to cleanse crops of other crops from weeds. The quantity of weeds in crops of field crops increases with cultivation of crops by organic technology.