A three-year field trial was carried out with two Bulgarian common vetch cultivars – Dobrudzha and Obrazets 666. The experiment was performed in the Training and Experimental Fields of the Agricultural University – Plovdiv on alluvial-meadow soil, in four replications, the size of the experimental plot being 10 m2. The studied growth regulators RENI and RENI D, as well as the commercial products Bormax, Mn chelate and Molybdenite were applied once in the season, at the budding stage of vetch. The results obtained show that treatment with the growth regulators contributed to the increase of the starch content, the effect being more pronounced in Obrazets 666 – an increase of 3,2 to 3,5% compared to the untreated variant. What is more, the application of the products increased the protein content in both studied common vetch cultivars – Dobrudzha responded better to Bormax and RENI D, while Obrazets 666 responded to three growth regulators (Bormax, RENI and RENI D). A change in the elemental and amino acid composition of the harvested grain was also reported, which is essential for the production of feed of higher biological value for the farm animals. In Dobrudzha cultivar, a 12,0% increase of the lysine content in grain was found after treatment with RENI. Obrazets 666 responded with a sharp increase in the values of the sulfur-containing amino acid methionine in the grain protein in the variants treated with RENI D and Bormax – 47,2 and 35,2% on average.
Keywords: common vetch, growth regulators, biological value of feed, cereals and legumes, protein quality