The Biological Spectrum of Segetal Weeds in Winter Wheat Crops in the Southeast of Western Siberia
The purpose of the study was to determine the species composition and relative abundance of weeds in winter wheat crops to develop effective protection methods. The work was conducted in 2016-2018 in the Kemerovo region. The sum of the positive average daily air temperatures during the growing season of the crop varied within 1800-2400 С; the average annual precipitation was 400-650 mm; hydrothermal coefficient was 1.2-1.6. Weediness of the crops was studied in 2016 on an area of 6,300 ha; in 2017, the plot area was 13,100 ha; in 2018, the plot area was 9,100 ha. The object of the study was the weed component of wheat agrophytocenosis. The forecrop was bare fallow. The main examination was conducted in the tillering phase (spring) before chemical treatment. The samples were taken using 0.25 m2 frames on an area of 100 hectares; the species and quantitative composition of weeds were determined visually. The most common young weeds in winter wheat crops were Stel-laria media, Raphanus raphanistrum, Chenopodium album, Polygonum convolvulus, Galeopsis speciosa, Panicum crussgalli, Amaranthus retroflexus, Matricaria inodora, etc.; the most common perennial grasses were Cirsiumhorridulum, Sonchusarvensis, Agropyron repens, and Taraxacum offlcinale. The composition of the weed flora included 34 species of 33 genera belonging to 17 families. The most common were the plants of Asteraceae (21%) and Poaceae (17%) families. The proportion of weeds belonging to rare families in the south-east of Western Siberia such as Fabaceae, Geraniaceae, Caryophyllaceae, and Violaceae was 37%. On average, over three years, 38.4% of winter wheat crops were weeded to a very weak degree, 43.0% were weeded to a weak degree; 10.3% were weeded to a medium degree; 2.5% were weeded to a strong degree. Of the 28,500 ha of the surveyed territories, 1,649 ha, or 5.8%, were not weeded.