Soil herbicides in sunflower crops in the Eastern Forest-Steppe of Ukraine

Abstract

Goal. To determine the influence of soil herbicides with different active substances on crop weediness and sunflower seed yield in the conditions of the Eastern Forest Steppe of Ukraine.
 Methods. Field, measuring and weighting, and statistical.
 Results. In 2019, with 13 mm of precipitation in the first period after applying soil herbicides, the effectiveness of herbicides in reducing the number and raw mass of weeds in sunflower crops was 60% and 45%, respectively, and in 2021 with 81 mm of precipitation, it was 89% and 95%. In 2021, there was phytotoxic suppression of culture plants by Kharnes, e.c. (acetochlor, 900 g/l), 2.5 l/ha. Despite this, Kharnes was the most effective in controlling the total number of weeds (91% and 96% for the first and second counts, respectively) and their raw mass (95%). Other preparations provided the following indicators: Proponit 720, EC (propisochlor, 720 g/l), 3.0 l/ ha (by quantity — 84% and 90%, by weight — 84%); Selefit, SC (promethrin, 500 g/l), 4.0 l/ha (by quantity — 79% and 81%, by weight — 70%); Prymekstra TZ Hold 500 SC (S-metolachlor, 312.5 g/l + terbuthylazine, 187.5 g/l), 4.5 l/ha (by quantity — 68% and 73%, by weight — 66%); Stomp 330, e.c. (pendimethalin, 330 g/l), 5.0 l/ha (by quantity — 51% and 63%, by weight — 60%); Komandyr, EC (clomazon, 480 g/l), 0.15 l/ha (26% and 52% by quantity, 37% by weight). Ambrosia artemisiifolia L. was resistant to the above soil herbicides. It was established that sunflower is a powerful competitor in agrophytocenosis. Its share in the total raw mass of agrophytocenosis, depending on the period of accounting, was from 65.8 to 82.0%, and in dry mass — from 61.8 to 80.2%. In addition, it was established that losses of the sunflower crop from weeds coincide with the specific share of weeds in the total mass of the agrophytocenosis. Soil herbicides provided the following increases in the yield of sunflower seeds (t/ha): Kharnes — 0.53; Proponit 720 — 0.46; Stomp 330 — 0.44; Prymekstra TZ Hold 500 SC and Selefit — 0.39; Komandyr — 0.17. It was found that sunflower was the most tolerant to Stomp 330, and the least — to Komandyr.
 Conclusions. In terms of the level of weed death in sunflower crops and the increase in the yield of its seeds, Kharnes was the best among soil herbicides, and Komandyr was the worst.