A precise field experiment for studying the efficacy and selectivity of various systems for chemical weed control in a vineyard of Sauvignon Blanc cultivar was carried out in the region of Brezovo (Plovdiv District, Bulgaria) in the period 2017-2019. The established weed species composition in the plantation was different in the two years of the study, which was due to the difference in weather conditions over the period. Weed associations included the species Chenopodium album (L.), Solanum nigrum (L.), Portulaca oleracea (L.), Setaria viridis (L.), Xanthium strumarium (L.) etc. The following winter-spring species also showed high density – Capsella bursa-pastoris (L.) Medic, Erodium cicutarium (L.), Viola spp. (L). The following polycarpic species were found: Convolvulus arvensis (L.), Trifolium spp. (L.), Cynodon dactylon (L.) Pers., etc.
The systems for chemical weed control included the following variants: 1. Smerch 24 EC (oxyfluorfen) – 3000 ml/ha+ Dual Gold 960 EC (s-metolachlor) – 1500 ml/ha – applied early in spring; 2. Stomp Aqua (pendimethalin) applied twice – early in spring (7000 ml/ha) and post-harvest (3000 ml/ha) in the first and the second years, and in the third once in spring early in a dose 7000 ml/ha; 3. Pledge 50 WP (flumioxazine) – applied once before vine vegetation, at a rate of 400 g/ha in the first year, 300 g/ha in the second and in the third year – 200 g/ha; 4. Pledge 50 WP (flumioxazine) applied twice – in spring, before vine vegetation and post-harvest at a rate of 400+400 g/ha in the first year, 300+300 g/ha in the second, and the third once – in the spring at dose 200 g/ha.
It was established that the herbicides based on flumioxazine and oxyfluorfen in combination with s-metolachlor showed high efficacy within 56 days after treatment.
At the Agricultural University-Plovdiv, Department of Microbiology and Environmental Biotechnology, in vitro biotest studies were conducted to obtain preliminary specific data regarding the effect of the introduction of various herbicides on soil microorganisms. Studies of each of the soil suspensions containing a representative sample of the respective microbial communities revealed a relatively small effect of the tested herbicides on them.