The factors influencing the number of weed plants in the crops of spring wheat on the example of forest steppe of Western Siberia

The objectives of the research were to determine the factors affecting the change in the number and species composition of weeds and the search for the ways of effective control of the number of weeds in spring wheat crops with different methods of minimizing soil cultivation. The researches were held in the stationary field experiment "SibRIACA" SF RCA RAS in the forest steppe of Western Siberia for 34 years. From 1981 to 1990 the crops were cultivated in a 5-field crop rotation: fallow-winter rye-wheat-oats (barley) -wheat; in 1991-2006 it was reorganized into 4-field: fallow -winter rye-wheat-wheat; since 2007, winter rye has been replaced by wheat: fallow-wheat-wheat-wheat-wheat. In grain-crop rotation, different options for autumn tillage were studied: 1. Plowing, 20-22 cm (in fallow 25-27 cm). 2. Slot-free processing with SibIME racks of 20-22 cm (in fallow of 25-27 cm). 3. The minimum cultivation with cultivator "Stepnyak" to the depth of 10-12 cm. 4. Without chamfering (“zero chipping”). The size of experimental options was 1300 m2. Two chemicalization backgrounds were also compared, i.e. control and intensive. On the control background no chemicals were used. Fertilizers, herbicides, fungicides and insecticides were used against intensive background. The studies showed that without means of chemical plant protection in the fields of grain-crop rotation there had been gradual accumulation of weed vegetation. The increase in the number of weeds occurred much faster in the variants of minimum chaffing tillage and without chilling (“zero” cultivation) than in “plowing” variant. Minimization of soil cultivation without using herbicides led to the increase in crops weediness of by 1.4-1.8 times. Refusal from autumn tillage caused a 2.3-fold increase in the number of weeds compared to plowing. Weed infestation depended significantly on humidification index of the year. In dry years (moistening coefficient 1.2) it made 28.0 %. The appearance in the forest-steppe of steppe species of weed plants on the field was also noted, which was possibly associated with climate warming in Western Siberia. Against intensive background, tank mixture of herbicides was used once per vegetation to reduce clogging. It minimized the number of weeds during the entire observation period in all tillage options.