The contribution of factors to the formation of pollution of grain-grass-rowed crops in the north-west of the Russian Federation

The study was carried out to evaluate the influence of natural and anthropogenic factors on the formation of weed infestation of fields in the crop rotation including cereals, row crops and grasses to understand the possibilities to manage the species composition and population of weed plants in the North- West of the Russian Federation. The experiments were performed in 2012-2018 in the Leningrad region during the fifth rotation with the following crops: narrow-leaved lupin, winter rye, spring barley with sowing of perennial grasses (red clover and timothy-grass), perennial grasses of 1 and 2 years, potato, spring rape. Weed infestation of fields in the crop rotation was depended more on biological features of cultivated cultures (species abundance 76,1 %, initial density 29,6 %, phytomass after harvest 21,0 %) than on individual parameters of weed infestation (3,5, 8,3, 17,7 %). The weather conditions were of decisive importance in weed initial formation (49,7 %), and, to a lesser degree, for such parameters as species abundance (30,7 %) and aboveground biomass of weeds (20,6 %). Weather conditions influenced the effects associated with the use of mineral fertilizers (interaction 4,0…11,9 %) and integrated plant protection system (interaction 2,9…12,0 %). Among the studied factors of crop production intensification application of herbicides in the variant with integrated plant protection system most affected the species abundance (26 %) and final phytomass of weed plants (26,2 %), whereas long term application of mineral fertilizers affected the initial weed infestation of agrocenoses (10,2 %), that was statistically sufficient in every year of the research (23,0…67,8 %). The combined effect of mineral fertilizers and herbicides most influenced the formation of the aboveground mass of weeds (interaction 0,9…5,0 %), especially in years with excessive humidity.

grain-grass-rowed crop rotation, North-Western region, weeds, weather conditions, mineral fertilizers, herbicides