Field Crop Studies

The investigations were carried out during 2016–2017 at Dobrudzha Agricultural Institute – General Toshevo (DAI). The aim of this investigation was to determine the effect of the introducing of herbicide combinations on the yield in sunflower hybrid ”Kaliya”. The following herbicides combinations were used: pendimetalin (450 ml) + linuron (300 ml); linuron (300 ml) + pendimetalin (450 ml); metolachlor + terbutilazin (350 ml) + kletodim (160 ml); petoxamide (300 ml) + linuron (300 ml). The herbicides were applied at stage 01 (BBCH), and pendimetalin (450 ml) and kletodim (160 ml) at stage 12-14 (BBCH) on sunflower hybrid ”Kaliya”. The herbicide effect was determined by the quantitative weight method and evaluated by the EWRS scale. These were the followed parameters: plant height (cm), head diameter (cm), weight of seeds per plant (g), weight of 1000 seeds (g) and oil content of seed (%). In 2016, highest yield was realized in the variant with petoxamide (300 ml) + linuron (300 ml). The decrease of yield according to the untreated check variant was lowest – with 8.8%. In 2017, metolachlor + terbutilazin (350 ml) + kletodim (160 ml) was the variant with highest yield and lowest decrease of yield – with 10.6%. %. The interaction between the factors years and herbicides (YxH) was with the highest strength of effect on parameters yield, oil content of seeds and plant height (55-72%). Significantly lower was the effect of the factors years and applied herbicide. Meteorological conditions of the year as a factor do not effect on the indicator plant height. The interaction between the factors years and herbicides (YxH) was with the highest strength of effect on parameters weight of seeds per plant (91%) and weight of 1000 seeds (55%). Significantly lower was the effect of the factors years and applied herbicide. Meteorological conditions were with the highest strength of effect on parameter head diameter (89%).

Key words: Sunflower, Herbicides, Weeds, Yield, Structural elements of yield