Possible timing of herbicide treatment of pea crops of the Santana variety in the southern forest-steppe of the Omsk Region

The research findings obtained on the educational and experimental field of Omsk State Agricultural University from 2020 through 2024 are discussed. The soil of the experimental plot was meadow-chernozem, medium-deep, low-humus, and medium-loamy. The Santana pea variety was sown at a rate of 1 million viable seeds per hectare. The experiments were established against two backgrounds: without fertilizers and with the application of ammonium phosphate fertilizer (N12P52) locally at sowing. The treatment of crops with the herbicide Germes, oil dispersion, (0.8 L ha) was performed at stage of the second pair of true leaves, and then in 5 and 10 days after the first treatment. The spraying fluid consumption was 200 L ha. The experiment was replicated four times; the plot area was 60 m2. Four out of five years of research were droughty, and in 2024 only, the hydrothermal coefficient was equal to 1.67. The research findings showed that with time displacement of pea crop herbicide treatment, the survival rate and yields of pea grain decreased, and the proportion of weeds in the agrophytocenosis, on the contrary, increased. The survival rate of pea plants fluctuated by years from 59.0 to 62.0% after the first treatment of pea crops and gradually decreased after subsequent treatments in 5 and 10 days. The proportion of weeds at treatment at stage of the second pair of true leaves was 6.49 and 6.98% depending on the fertilization background and increased to 7.09 and 7.42% at treatment in 10 days. The yield of pea grain against unfertilized background at the first treatment with herbicide was 3.28 t ha and decreased after later treatments to 3.20-3.03 t ha. The application of ammonium phosphate fertilizer increased grain yield by 0.10-0.17 t ha.