Efficiency of Herbicide Treatment of Spring Barley Crops Under Conditions of Moisture Deficiency in the North-West of Russia

The literature is dominated by the idea of the positive effect of herbicides on the yield of spring barley and rarely mentions their phytotoxicity, which can limit the economic effect or neutralize it completely. The purpose of the research is to determine the effectiveness of treatment of spring barley crops with Lintur herbicide, EDG at different application rates and nitrogen nutrition backgrounds in conditions of moisture deficiency. The work was carried out in 2019–2021. In the Leningrad region, on sod-podrolic sandy loam soil with an organic matter content of 2.9 %, mobile phosphorus and potassium (according to Kirsanov) – 145.1 and 48.4 mg/kg, respectively. The experimental scheme involved the study of four standards for the use of Lintur herbicide, EDG (0.68, 101, 135 g/ha, or 0.50, 75, 100 %) on two fertilization backgrounds (N and N). In all the years of research, moisture deficiency was noted during herbicide treatment and in the following days. A decrease in the herbicide consumption rate led to a decrease in its biological effectiveness in terms of quantity (from 79.1 to 63.3 %) and the above-ground mass of weeds (from 79.2 to 61.9 %). This decrease was statistically significant only with the use of a half-dose herbicide. The full–dose version of the drug turned out to be the least effective from an economic point of view (the saved yield was 3.1 % versus 6.1 % and 11.8 % at application rates of 100, 75 % and 50 %, respectively), due to the manifestation of phytotoxicity on barley in conditions of moisture deficiency, aggravated by elevated temperature conditions. The negative effect of herbicidal stress extended exclusively to the density of the productive stem of the crop. The effect of stress was more pronounced with a deficiency of nitrogen nutrition. The addition of ammonium nitrate from N led to an increase in biological (by 12 % in density, by 14.1 % in phytomass) and the economic (11.5 %) effectiveness of herbicide treatment.