220 Scientifc Papers. Series A. Agronomy, Vol. LX, 2017 ISSN 2285-5785; ISSN CD-ROM 2285-5793; ISSN Online 2285-5807; ISSN-L 2285-5785 STABILITY EVALUATION OF SOME FOLIAR FERTILIZER AND GROWTH REGULATORS FOR THEIR INFLUENCE ON THE GRAIN YIELD OF DURUM WHEAT Grozi DELCHEV Trakia University, Faculty of Agriculture, Stara Zagora, 6000, Bulgaria Corresponding author email: delchevgd@dir.bg Abstract In 2010-2012 was studied the influence of some foliar fertilizers and growth regulators on grain yield and its stability of durum wheat cultivar Victoria (Triticum turgidum conv. durum Desf. var. valenciae). Factor A included the years of investigation. Factor B included 5 foliar fertilizers - Vertex high-H34 – 3 l/ha, High-phos – 5 l/ha, Potassium thiosulfate (PTS) – 5 l/ha, Foliar extra – 2.5 l/ha and Trace elements for cereals (TEC) – 1 l/ha, a growth stimulator Amalgerol premium – 3 l/ha, an antitranspirant Pureshade - 20 l/ha and tank mixture Amalgerol premium – 3 l/ha + TEC – 1 l/ha. Foliar fertilizers and growth stimulator were treated during tillering stage of the durum wheat and antitranspirant was treated during ear emergence and grain development stages of durum wheat. The grain yields are increase by foliar fertilizers Vertex high-H34, High-phos, Potassium thiosulfate (PTS), Foliar extra and Trace elements for cereals (TEC) and the growth stimulator Amalgerol premium were treated during tillering stage of the durum wheat and the antitranspirant Pureshade was treated during ear emergence and grain development stages of the durum wheat. Antitranspirant Pureshade is the most unstable for grain yield by treatment in both stages - ear emergence and grain development. Pureshade must be treated during the occurrence of drought, not during special stage of the durum wheat development. Tank mixture Amalgerol premium + TEC, followed by foliar fertilizers Vertex high-H34, High- phos, TEC and stimulator Amalgerol premium are technological the most valuable. They combine high grain yield with high stability with relation to different years. Using of these preparations is being proposed as an element of the technology for growing of durum wheat. Key words: durum wheat, foliar fertilizers, growth stimulator, antitranspirant, grain yield. INTRODUCTION Modern agriculture cannot successfully develop, if not more widely applied agro- technical and agrochemical activities aimed at increasing the yields of crops. In modern technologies for growing of field crops increa- singly becomes important use of complex fertilizers for foliar application (Yuande et al., 1994; Barraclough and Haynes, 1996; Shuqing et al., 1998; Panayotova and Stoyanova, 2014). The main advantage of foliar application is that it acts directly on the leaves of the plant, and it is proved that they are absorbed by much better and more fully the nutrients. Complex ferti- lizers contain all necessary for the development of culture nutrients: nitrogen, phosphorus, potassium, several trace elements, amino acids and physiologically active substances connected by special biotech environment. Foliar fertilization of field crops is essential reserve to supplement and correction of soil fertilization. In specific cases, such as soil drought or soil agrochemical unfitness, the use of foliar fertilization is an important link in the overall technology of cultivation of every crop. The appropriateness and effects of foliar application is an aim of study in works of many authors (El-Naga, 1995; Phillips et al., 1999; Taniguchi et al., 1999). Growth regulators properly selected and used in appropriate level of fertilization, increase yield and quality of received production where classical methods and tools are less effective or almost exhausted their possibilities (Vildflush and Gurban, 1999; Delchev, 2003). There is data that common and durum wheat respond differently to treatment with the same prepara- tions. According to some authors (Jürgens and Knittel, 1985; Rapparini et al., 1987) durum wheat in its response to some retardants is closer to barley than to common wheat. The purpose of this investigation was to establish the selectivity and stability of some foliar fertilizers, growth stimulator Amalgerol premium and antitranspirant Pureshade on the