Department of Agrochemistry and Soil Sciences, Faculty of Agronomy, Agricultural University – Plovdiv, 12 Mendeleev Str., 4000 Plovdiv, Bulgaria
(Manuscript received 2 July 2020; accepted for publication 14 August 2020)
Abstract. The aim of the study was to determine the effect of foliar application of growth regulators on photosynthetic activity, nitrogen fixation and the biological value of protein in two cultivars of winter forage peas – Mir and Vesela. For achieving the aim set, a three-year field trial was carried out in the Training and Experimental Fields of the Agricultural University of Plovdiv, on a plot untreated with commercial fertilizers. The following growth regulators were used: RENI, RENI D, Bormax, Manganese Chelate and Molybdenite, applied at the phenological stage of pea plant budding. The effect of those products on the studied characteristics was compared to the untreated control. The reported three-year results show that foliar applied growth regulators had a positive effect on photosynthetic and nitrogenase activity, as well as on the characteristics of the nitrogen fixation apparatus (total number of nodules, number of active nodules and weight of the nodules) and on the biological value of the obtained protein in both cultivars of winter forage peas.