Efficacy of herbicides in sunflower sowings in the conditions of the western Forest-Steppe of Ukraine

Abstract

Purpose. Determinе the species composition of weeds and the most efficient system of weed control in sunflower sowings.
 Methods. Field, laboratory, mathematical and statistical.
 Results. The species composition of spring weeds in sunflower sowings was mainly represented by dicotyledonous species Amaranthus retroflexus L., Chenopodium album L., Galinsoga parviflora Cav., Matricaria inodora L., Thlaspi arvense L., Polygonum convolvulus L., Sinapis arvensis L., Xanthium strumarium L. and cereal weeds Setaria glauca L., Echinochloa cruss-galli L. The efficiency of the use of herbicides Challenge 2.5 l/ha + Harness 1.5 l/ha on the 30th day after application, against the total number of weeds, was 89.7%. Meanwhile, the use of the herbicide Challenge is the application rate of 2.0 l/ha appeared more effective with the efficiency rate of 95.6%. The herbicides, regardless of their application scheme, did not caused thinning of the sowing density; however, plant suppression did occur. This was evidenced by reduced plant height during the anthodium formation and flowering stage compared to control.
 Conclusions. The dominant weed species in sunflower crops were Amaranthus retroflexus with the share of 15%, Chenopodium album 8%, Setaria glauca L. 23% and Echinochloa cruss galli 10%. Application of herbicide Challenge 2 l/ha in the 2 to 4 leaf stage of sunflower appeared the most effective as weed control method with the efficiency rate of 92.8%. Herbicides Challenge (2.5 l/ha) + Harness (1.5 l/ha) were milder to crop plants, which ultimately contributed to the formation of sunflower yield of 3.47 t/ha in hybrid ‘NK Condy’ and 3.04 t/ha in hybrid ‘Atilla’.