Sunflower is a major field oilseed crop in Bulgaria. Uncontrolled weed flora is the main competitor during sunflowers' vegetation. The present study aims to determine the weed infestation in different growth stages of sunflowers and to determine their influence on the productivity of the crop. The study was conducted during two sunflower growing seasons with the sunflower hybrid „Coloris“ CL in 2022 and 2023. The experiment was carried out on the agricultural land of Novoseltsi village, in the region of Vidin city, Bulgaria. The weed mapping was determined by the П-method for weed survey in spring field crops. A comparison of the weed infestation was determined between untreated plot and plot with an application of the tank mixture of the herbicidal products Pulsar Plus (25 g/l imazamox) – 1.60 l ha-1 + Stratos Ultra (100 g/l cycloxydim) – 2.00 l ha-1. The herbicides were applied in the 4th-6th true leaf stage of sunflower. In the two experimental years, the sunflower was grown after preceding crop winter wheat. During the two years of the study, and during the two survey periods (Ist – in growth stage 8th - 10th true leafs stage of sunflower, and IInd - during the flowering of the crop) the predominant weed species were ragweed (Ambrosia artemisifolia L.) and wild hemp (Cannabis ruderalis Janisch.), followed by the weed Rough cocklebur (Xanthium strumarium L.). During the trial, no visual signs of phytotoxicity were detected in sunflower after the application of Pulsar Plus + Stratos Ultra in tank mixture. Sunflower seed moisture content was higher for the plants from the untreated plot. Statistically higher results for the studied indicators, such as seed yield, absolute and hectoliter seed mass were established after the application of Pulsar Plus + Stratos Ultra.

weeds, sunflower, yield

agronomy

Presentation: poster