Z. Zlatev, V. Popov
Abstract. The aim of this study was to investigate the effect of organic fertilization on photosynthesis of young tomato plants (Lycopersicon esculentum Mill.) – cv. Trapezica and cv. Yana. The field experiments were carried out at the experimental field of the Agroecological Centre of Agricultural University-Plovdiv, which is certified as an organic farm. For the purpose of the research, two biofertilizers were used – Emosan and Lumbrical (both authorized for use in organic farming). The results indicated that the applying of organic fertilizers increased leaf gas exchange parameters and pigment content in the studied cultivars. It is established that there was a positive effect of biofertilizers upon the functional activity of the photosynthetic apparatus.