THE HARMFULNESS OF WEEDS IN OAT AGROCENOSIS WITH UNDERSEEDING OF PERENNIAL GRASSES IN THE NORTH-WEST OF THE RUSSIAN FEDERATION

Abstract

The results of the study of harmfulness of weeds in the oat with perennial grasses agrocenosis in the conditions of the North-West of the Russian Federation are presented. Assessment of harmfulness of weeds in oat crops in this region of cultivation this crop has not been previously carried out, and agricultural production has to comply with economic thresholds of harmfulness for other spring cereals that is not rightfully. The method of permanent plots and multiple regression analysis were used in the statistical processing of the obtained data on the weed infestation of oat crops. By the results of the study the harmfulness coefficients of weeds were 0,005 c/ha (0,18%) of oat crop losses from 1 copy/m2 of weed, and 0,267 c/ha (0,91%) for 1% of foliage projective cover in the tillering phase of oat, which can be used for the forecast of crop losses, as well as in the calculations of economic thresholds of harmfulness for this crop. Oat crop losses from weeds amounted to 2,22 c/ha (10,3%), according to the years of research they ranged from 0,4 to 5,2 c/ha (1,5–19,8%). The main losses of the crop were associated with the growth of the most widespread species in the crop – lamb's quarters (Chenopodium album). Weeds influenced to all elements of the crop structure, mostly to the density of the productive stems (a decrease by 14,7%). The harmfulness of weeds increased in the case of severe damage to the stem of oats by the Swedish fly (by 1,8 times), as well as with an increase in the content of the main elements of mineral nutrition in the soil (by 2,2 times).