Influence of agrotechnologies on the development of weeds in the agrophytocenosis and on the productivity of spring wheat in the forest-steppe of Western Siberia

Increased weed infestation of spring wheat crops in the forest-steppe agro-landscapes of Western Siberia is one of the main reasons for the shortfall of grain from the potential yield of the crop. The research was conducted in the period 2004-2019 on the fields of the Omsk Agrarian Research Center. The soil of the experimental plot is meadow-chernozem with average fertility, high loam content, a humus content of 7-8%, a pH of 6.4. It has been established that in the forest-steppe landscapes of Western Siberia the degree and species composition of the weed component in spring wheat crops is formed and depends on the forecrop, the system of tillage in the crop rotation and the use of intensification means. The most weedy agrophytocenoses in terms of both the number and biomass of weeds are observed in repeated crops, without the use of chemical agents and with a minimum system of tillage in the crop rotation with increased competition for moisture and nutrients. Thanks to a better provision of moisture and nutrition, the yield of repeated wheat crops compared with the second wheat crops after fallow, even with the use of herbicides, is reduced by an average of 0.41 t/ha or 20.4%. More favorable conditions for the growth of the crop biomass are formed with the complex use of chemical agents, which leads to a decrease in the number and biomass of weeds by 3.6-3.9 times, mainly due to the suppression of panicgrass species. The correlation between the abundance of weeds in second wheat crops after fallow and the crop yield has a negative trend with the number and biomass of dicotyledonous weeds - up to 48-53%, while with panicgrass species it reaches 64-90%. The increase in the yield of spring wheat with the systematic use of herbicides (dicoticides + graminicides) in the crop rotation amounts to 0.44-0.60 t/ha or 26.2-58.1%.