The effect of herbicide Flex, AS (active ingredient fomesafen 250 g/l) on annual weed species common in soybean crops was studied. The studies were conducted under greenhouse conditions in 2019-2021. The sensitivity of ragweed Ambrosia artemisiifolia L., Asian copper leaf Acalypha australis L., common lamb's quarters Chenopodium album L., common dayflower Commelina communis L., China jute Abutilon theophrasti Medik, trailing hollyhock Hibiscus trionum L., St.-Paul’swort Sigesbeckia pubescens Makino, green amaranth Amaranthus retroflexus L., elsholtzia Elsholtzia pseudocristata Levl. et Vaniot, and Siberian cocklebur Xanthium sibiricum Patrin ex Widd was determined. Weed treatment with Flex at rates of 0.75, 1.0, 1.25 and 1.5 l/ha was carried out three times a season at different stages of plant growth and development. The level of sensitivity of weed species to herbicide was judged by the decrease in height and weight of the aboveground organs of the experimental plants compared to the control. It was found that Flex herbicide completely destroys plants of all tested species in the early stages of growth and development (1-4 true leaves). When treating weeds that have formed 3-10 leaves, ragweed, green amaranth, Asian copper leaf, trailing hollyhock and Siberian cocklebur remain highly sensitive to the drug action (reduction of the aboveground weight up to 94-100%). Application of Flex on overgrown plants leads to a significant decrease in its activity against all studied weed species. When used in the third term, the herbicide is effective only on the green amaranth, suppressing the mass of the plants by 76-86%.

The biological and economic efficiency of the new herbicide Flex in post-emergence application to soybean crops of the variety Sphera was studied. The tests were carried out incompliance with the standard methods in the form of the plot experiment in 2017, 2018 on brown meadow podzolized soils in the south of the Far East. The preparation was tested in the consumption rates of 1.25 and 1.5 l/ha when the crop reached the development phase of two triple leaves as opposed to the standard herbicide Galaxy Top in the rate of 1.7 l/ha. It was found that Flex has a high herbicidal activity against all dicotyledonous annual and perennial species of weeds. Common ragweed (Ambrosia artemisiifolia L.) and Asian copperleaf (Acalypha australis L.) were highly sensitive to the preparation even in the minimum consumption rate. Especially strong toxic effect of Flex was produced on such weeds in the rosette phase as Asiatic dayflower (Commelina communis L.), lamb’s quarters (Chenopodium album L.), field milk thistle (Sonchus arvensis L.), creeping thistle (Cirsium setosum (Willd.) Bieb.) and common mugwort (Artemisia vulgaris L.). Consistent application of graminicide Fuzilade Forte in the rate of 1.5 l/ha after treatment of soybean crops with herbicide Flex contributed to an almost complete elimination of annual grass weeds. The high biological efficiency of the experimental preparation contributed to a significant increase in crop yield. In 2018, when it was applied in the minimum rate of 1.25 l/ha, the yield achieved was 0.94 t/ha, exceeding the control value by 3.3 times. The highest yield increase of soybean seeds (1.12 t/ha on average for 2 years) was obtained with the use of herbicide Flex in the maximum consumption rate of 1.5 l/ha. Application of herbicide Flex to soybean crops in the rates of 1.25 and 1.5 l/ha alongside with the preparation Trend 90 in the rate of 0.2 l/ha proved to be highly effective in eliminating annual and perennial dicotyledonous weeds (in early stages of development) from soybean crops.

The work presents the results of testing tank mixtures of herbicides Proponit and Pledge applied in different doses to soybean crops during preemergence Treatment. The tests were carried out in Primorsky territory by standard methods in the form of the plot experiment in the trial field with brown meadow podzolized soils (by mechanical composition characterized as medium clay, content of humus 3.8%, labile phosphorus and exchange potassium in the soil 16 and 120 mg/kg respectively, PH 5.3). Hydrothermal conditions during the experiment were favorable for the implementation of the herbicidal potential of soil preparations. Trial tank mixtures showed high herbicidal activity against annual grass weeds (Echinochloa crusgalli, Setaria spp), annual dicotyledonous species (Ambrosia artemisiifolia, Acalypha australis, Abutilon theophrasti, Elsholtzia pseudocristata, Chenopodium album), Commelina communis and certain perennial dicotyledonous weeds. The use of mixtures of Proponit and Pledge in higher doses contributed to an increase in protective action and increase in the total herbicidal activity of preparations. The highest yield of soybean in the experiment, 2.41 t/ha, which exceeded the control value by 3.5 times, was achieved in the variant of the soil treatment with a mixture of herbicides in the maximum recommended rates (Proponit 3.0 l/ ha + Pledge 0.12 kg/ha). The economic efficiency of chemical weeding amounted to 39.0 thousand rubles/ha. Thus, in the conditions of soya crops contamination mainly by sensitive annual weed species and with optimal soil moisture, preemergence use of Proponit + Pledge tank mixtures was sufficient for reliable protection of soybean crops and eliminated the need for foliar herbicides.

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The results of the study of the weed component of soybean, early grain crops and maize agrocenoses in Primorsky Territory are presented. In total, 111 species of weeds belonging to 35 families were found during the period from 2016 to 2020. Compared with the results of crop surveys conducted in 2006-2015, the total number of species detected has increased by 23. The largest number of species belongs to the families Asteraceae (24), Poaceae (15), Polygonaceae (11), Fabaceae (9), Brassicaceae (8), Caryophyllaceae (7) and Lamiaceae (5). The remaining 26 families were represented by 1-3 species each. For the first time weeds-representatives of the families Scrophulariaceae, Violaceae, Lythraceae, Onagraceae, Asclepiadaceae and Boraginaceae have been discovered. The floristic composition of soybean agrocenoses was the highest with 108 weed species from 31 families. In cereal and maize crops, weed diversity was less significant, with 75 species in 22 families and 72 species in 25 families, respectively. Weed vegetation in all the above crops is represented by 62 species of 19 families. The main weed species that grew on 97-99% of the surveyed territory with a sufficiently high average density of standing (21-61pcs/m2) were Asian copperleaf, cockspur grass and common ragweed. Also, more than half of the surveyed crops of soybeans, cereals and corn were hairy cupgrass, perennial sow thistle, common couch-grass, common lamb’s quarters, wormwood species, field horsetail, yellow thistle, dayflower and yellow foxtail. Practical measures to protect against weeds on the Primorsky Territory should be primarily aimed at controlling these species.