Harmfulness of weed plants in winter wheat crops in the North-West of Russia
Keywords:winter wheat, weed plant, species composition, type of weed infestation, harmfulness, coefficient of harmfulness, crop loss
The relevant studies were carried out on the experimental fields (Gatchina district, Leningrad region) using the original plot estimate method in the period 2012–2017. The results of the research revealed a wide variety (more than 50 species) and a large similarity of the species composition of weeds in winter wheat crops. If the number of weed plants at the shooting stage in winter wheat crops reached 269–428 weed/m2, or 14 to 24 % projective cover, of which at least 90 % were young dicotyledonous species, then the juvenile type and an average degree of weed infestation formed. The average long-term data of winter wheat yield losses from the weeds ranged 1–24 % (0.6–6.9 с/ha) depending on the crop status and the type of weed infestation. The main shortfall in wheat production is associated with the growing of wintering species in winter wheat crops (Matricaria inodora, Myosotis arvensis, Viola arvensis, Capsella bursa-pastoris), which are the main objects for herbicide treatments in the region. According to our data, at 1 % of the projective cover, the yield of winter wheat is reduced by 0.13 с/ha (0.34 %), at 1 weed/m2 – by 0.08 с/ha (0.22 %). The crop status and the type of weed infestation have determined the choice of specified coefficients of harmfulness. Taking into account the actual weed infestation of crops, the use of specified coefficients makes it possible to predict the winter wheat yield losses at the shooting stage and make balanced decision about herbicide application.