The purpose of this study was to establish the specific characteristics of organic farming sunflower hybrids in terms of seed yield and its structural elements as well as the efficiency of bioproduct Biophalfa (Alga 300) in rate 1 l.ha-1. Seven sunflower hybrids were tested: Sanay, NK Meldimi, NK Alego, NK Ferti, DKF2120, P64LE10 and P64LE11 on the certified bio-field of the Field Crops Institute, Chirpan, Bulgaria, under non-irrigated conditions after durum wheat (Tr. durum Desf.). The soil in the field of organic farming was Pellic Vertisols (FAO). The following characteristics were reported: seed yield (t.ha-1), weight of the whole head (g); head diameters D1 (length) and D2 (width) (cm) and the ratio between the diameters (D1/D2); head area (cm2); specific head weight (g.cm-2); weight of 1000 seeds (g). The results demonstrated that sunflower hybrids can be successfully grown under organic farming conditions. In favorable years a seed yield of 2.34 t.ha-1 can be realized, and in drought - about 1.45 t.ha-1. The sunflower hybrid DKF2120 achieved higher seed yields without and with feeding - 1.83 and 1.96 t.ha-1, respectively, i.e. it was most adaptable to be used in organic production out of the seven tested sunflower hybrids. The proven interaction Hybrid х Year showed that hybrids manifested different requirements to the conditions of the environment. For both fertilizing systems, the P64LE10 and P64LE11 hybrids had a significantly higher weight of 1000 seeds - from 56.2 to 57.3 g, and the values were found to be higher in the favorable 2014 (51.2 g). The weight of whole head ranging from 133 to 348 g, The foliar feeding additional stimulates weight of whole head, resulting in average of 227.7 g. while without feeding it was 200.3 g. The area of sunflower head was very good - 224 cm2. There was a strong positive correlation between the diameters of the head with its area (0.95-0.96).

organic farming, sunflower hybrids, foliar fertilization, seed yield, 1000 seeds weight.

field crops and pastures

Presentation: poster