Activity of weed plants in field crops in the steppe zone of the Krasnodar territory

More than 150 species of weeds grow in agrophytocenoses of field crops in the western part of the steppe zone of the Krasnodar Territory, of which only 38 are active to one degree or another in the cenoflora of agrophytocenoses. It has been revealed that 9 species showed the greatest activity, the indicators of their demands on the heat factor (the sum of active temperatures above +5 ° C = 1366– 3536) were closest to the indicators of heat supply in the survey area (3400–3800 °C). They clogged the crops of all examined field crops (sunflower, corn, winter wheat, oats, soybeans, alfalfa, potatoes): Ambrosia artemisiifolia L., Convolvulus arvensis L., Cirsium setosum (Willd.) Bess., Amaranthus retroflexus L., Chenopodium album L., Echinochloa crusgalli (L.) Beauv., Abutilon theophrastii Medik., Persicaria maculosa S.F. Gray, Lactuca serriola L. Less active were the species, which optimal level of requirement for heat factor (the sum of active temperatures above +5 °C = 1152–2078) was noticeably lower than in the species of the previous group: Lactuca tatarica (L.) C.A. Mey., Descurainia sophia (L.) Webb. ex Prantl, Sinapis arvensis L., Amaranthus blitoides S. Watson., Taraxacum officinale Wigg., Portulaca oleraceae L. Agrophytocenoses of all field crops included 19 more, mainly quite active and low-active species. The limits of the optimal requirements of these species to the heat factor in the zone of harmfulness (the sum of active temperatures above +5 °C = 953–2107) are significantly lower than those of the species in the first and second groups, and differ more significantly from the indicators of heat supply of the examination zone. The revealed ratio of species of different activity will be maintained provided that the weather and climatic conditions in the study area are preserved, as well as maintaining the current level of technology for cultivating field crops, and will amount as the content of a long-term regional forecast, including the above-mentioned species that will most actively have a harmful effect on the growth and development of the cultivated plants.