Science & Technologies Volume VI, 2016, Number 6: AGROBIOLOGICAL SCIENCE 1 STABILITY VALUATION OF SOME MIXTURES BETWEEN STIMULATORS AND COMBINED HERBICIDES FOR THE GRAIN YIELD OF DURUM WHEAT Grozi Delchev Trakia University, Faculty of Agriculture, 6000, Stara Zagora, Bulgaria e-mail: delchevgd@dir.bg ABSTRACT The research was conducted during 2010 - 2012 on pellic vertisol soil type. Under investigation was Bulgarian durum wheat cultivar Elbrus, which belongs to Triticum durum var. valenciae. Factor A included the years of investigation. Factor B included no treated check and 4 stimulators – Trisalvit (phenoxy acid derivatives, quaternary ammonium salts, trace elements) - 300 ml/ha, Salvit (synthetic auxins, trace elements, vitamins, surface active substances) - 500 ml/ha, Napsil (chlorofenoxyacetic acid derivatives, naftilacetic acid, phtalamine acid, chlorochlorine chloride, folic acid, trace elements) - 500 ml/ha, Cemofol (methilphtalamine acid derivatives, chlorochlorine chloride, folic acid, salicylic acid, trace elements, surface active substance) - 700 ml/ha. Factor C included weeded, no treated check and 3 combined herbicides – Palace 75 WG (pyroxulam) - 250 g/ha, Axial one (pinoxaden + florasulam) - 1 l/ha, Pacifica WG (mesosulfuron-methyl + iodosulfuron-methyl) - 350 g/ha. Because of the low adhesion of the herbicides Palace and Pacifica they were used in addition with adjuvants respectively Dassoil - 500 ml/ha and Biopower - 700 ml/ha. All of stimulators, herbicides and their tank-mixtures were treated in tillering stage of the durum wheat and are applied in a working solution of 200 l/ha. Mixing was done in the tank on the sprayer. There is antagonism of combined use by herbicide Pacifica with stimulators Trisalvit and Salvit. There is not antagonism by tank mixtures Napsil + Pacifica and Cemofol + Pacifica. There is additive effect by tank mixtures of stimulators Trisalvit, Salvit, Napsil and Cemofol with combined herbicides Palace, Axial one and Pacifica. The highest grain yield is obtained by tank mixture Trisalvit + Axial one. Tank mixtures of herbicide Palace with stimulator Napsil and herbicide Pacifica with stimulators Trisalvit and Salvit are the most unstable for grain yield. Tank mixtures of herbicide Axial one with stimulators Trisalvit, Napsil, Cemofol and Salvit and of herbicide Palace with stimulators Cemofol and Salvit are technological the most valuable. They combine high grain yield with high stability with relation to different years. Alone application of stimulators Trisalvit, Salvit, Napsil and Cemofol without herbicides have low estimate and do not be used in the durum wheat crops. Key words: durum wheat, stimulators, herbicides, grain yield, selectivity, stability INTRODUCTION In connection with the increased demands for environmental safety in the use of pesticides in modern agriculture in recent years emerged as a relevant question about the influence of herbicides and their mixtures on growth, development, yield and quality of crops. In modern grain production herbicides are an effective means of weed control in wheat. In case of use it is necessary to know not only their efficacy against weeds, but their specific effect on the wheat plants (Martin et al. 2001; Domoradzki and Rola, 2002; Senior and Dale, 2002). In the research works very often in parallel with the verification of biological efficacy of the herbicides examining also and their influence on grain yield and grain quality (Hannan-Jones, 1998; Archambault et al., 2001; Hartzler and Battles, 2001). Growth regulators properly selected and used the appropriate level of fertilization, increase yield and quality of the obtained production when classical methods and tools are less effective or nearly are exhausted their possibilities (Vildflush and Gurban, 1999; Delchev, 2003). In the scientific literature there are data indicative that common wheat and durum wheat respond differently to treatment with the same preparations (Rapparini et al., 1984; Pomati, 1987). The purpose of the investigation was to establish the selectivity and stability of some stimulators, combined herbicides and their tank mixtures on the durum wheat by influence of different meteorological conditions.