Department of Plant Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
(Manuscript received 28 January 2016; accepted for publication 30 May 2016)
Abstract. During 2013 – 2015 on pellic vertisol soil type was conducted a field experiment. Under investigation was Bulgarian milk thistle cultivar Silmar (Silybum marianum Gaertn.). Factor A included the years of investigation. Factor B included no treated check, 6 soil-applied herbicides – Tendar EC, Sharpen 33 EC, Merlin flex 480 SC, Smerch 24 ЕC, Raft 400 SC, Eagle 75 DF and 5 foliar-applied herbicides – Kalin flo, Eclipse 70 DWG, Sultan 500 SC, Granstar super 50 SG, Starane 250 EK. Factor C included no treated check and 1 antigraminaceous herbicide – Tiger platinium 5 EC. All herbicides, herbicide combinations and herbicide tank-mixtures were applied in a working solution of 200 l/ha. Mixing of foliar-applied herbicides was done in the tank on the sprayer. Soil-applied herbicides were treated during the period after sowing before emergence. Foliar-applied herbicides were treated during rosette stage of the milk thistle. Tank mixtures of antigraminaceous herbicide Tiger platinum with foliar herbicides Kalin flo, Eclipse, Sultan, Granstar super and Starane leads to obtaining high seed yields of milk thistle. High yields seeds are also obtained by foliar treatment with Tiger platinum after soil-applied herbicides Raft, Sharpen and Eagle. The use of the soil-applied herbicides Smerch, Merlin flex and Tendar does not increase the seed yield due to its higher phytotoxicity against milk thistle. Herbicide Tendar and herbicide combination Tendar + Tiger platinum are the most unstable, followed by herbicide Merlin flex. Herbicide tank-mixtures Kalin flo + Tiger platinum and Eclipse + Tiger platinum and herbicide combination Raft + Tiger platinum are technologically the most valuable. They combine high seed yield with high stability with relation to different years. Single application of soil-applied or foliar-applied herbicides have low estimate; due to that they must be combined for full control of weeds in milk thistle crops.