The main cause of wide presence of weeds in segetal and ruderal habitats is their high seed production capacity. It defined in expressly establishing field experiments, in industrial sowings, in segetal and ruderal habitats of steppe zones of Ukraine. It is determined that average fruitfulness of weeds in ruderal habitats was larger, than in segetal habitats by 3.8 times, and indexes of the maximum fruitfulness – by 4.0 times and reached accordingly 7028 and 9345 pieces, and 20112 and 98337 pieces. In segetal habitats monocotyledonous species of weeds on seed production on conceded dicotyledonous species by 2.9–3.7 times, and on ruderal habitats – by 9.8–10.5 times. Average seed production of monocotyledonous plants made up accordingly 3594 and 5660, and dicotyledonous – 12417 and 55629 pieces of seeds from one plant. Most species of monocotyledonous weeds (56,1 %) formed on one plant from 1 to 10 thousand pieces of seeds, and dicotyledonous weeds (37,9 %) – more than 10 thousand pieces of seeds. In segetal habitats the maximum seed production had families Asteraceae, Brassicaceae, Chenopodiaceae, Lamiaceae, and on ruderal habitats – Asteraceae, Chenopodiaceae, Caryophyllaceae, Apiaceae, Brassicaceae. The highest seed production the most widespread and abundant in sowings and on ruderal habitats had weeds: Convolvulus arvensis L., Ambrosia artemisiifolia L., Cynodon dactylon (L.) Pers., Echinochloa crus-galli (L.) P.Beauv., Eragrostis minor Host, Descurainia sophia (L.) Webb ex Prantl, Cirsium arvense (L.) Scop., Chenopodium album L., Amaranthus retroflexus L., etc. The greatest reserve weed seeds in soil in segetal habitats descended at the expense of species from genera Amaranthus, Galium, Cirsium, Setaria, and on ruderal habitats – Amaranthus, Chenopodium, Plantago, etc. In segetal habitats proof presence of weeds of genera with low seed production was sustained at the expense of their larger number of species, and genera with low number of species – at the expense of high seed production. In ruderal habitats – as at the expense of larger number of species, and their high seed production. The absolute maximum of seed production in segetal habitats have been reached at weeds of genera Amaranthus, Cirsium, Galium – from 3288 to 242266 pieces, and in ruderal habitats – Amaranthus, Chenopodium, Plantago – from 108903 to 1911683 pieces from one plant.
The weeds in onion and their control
