Influence of Some Foliar Fertilizers on the Development of Prista Grapevine Variety

The study was conducted during the period 2022–2024 in the experimental vineyard of the Institute of Agriculture and Seed Science “Obraztsov Chiflik” Ruse, part of Agricultural Academy – Sofia.The experiment included vines of the dessert variety Prista. It belongs to the group of early varieties. The variants are: first, which was treated with foliar fertilizers according to the following scheme: with sufficiently developed leaf mass – with the foliar fertilizer Yara Vita Flutrel – 300 ml/da; in the tassel phenophase – with Yara Vita Bortrac – 150 ml/da; phenophase of grain growth with Flutrel – 300ml/da; beginning of ripening – Stopit – 500 ml/da, and second, untreated with foliar fertilizers. The aim is to establish the influence of foliar fertilizers on the development of grapevines of Prista variety. The following indicators were determined: Grape yield (kg), sugar content (%), titratable acids (g/l), resistance to detachment (g), resistance to pressure (g). Foliar fertilization according to the indicated scheme has a positive effect on the development of Prista grapevines, with a proven effect expressed in the following: The average results from the experiment show that the treated variant of Prista grapevines is characterized by an average yield of grapes from one vine of 8.78 kg, and the untreated one with a yield of 8.29 kg of grapes. The excess is 0.480 kg compared to the control. In terms of the number of clusters, the treated variant is characterized by 18.6 pieces compared to 9.7 pieces in the control. The same trend is observed in the average mass of the cluster: It is 364 g in the treated vines and 294 g in the control. In terms of the average mass of the grain, the differences are insignificant. In terms of sugar content 20.8 in the treated vines compared to 18.6 in the control. No significant difference was observed in titratable acids. In terms of cluster length, the results were 23.05 cm in the treated vines and 22.64 cm in the control. The cluster width was greater in the vines with foliar fertilization – 11.13 cm and in the control with a value of 11.38 cm. In terms of resistance to pressure and tearing, the values are higher in the variant without foliar fertilization according to the above scheme. The established correlation dependencies r = 0.7 prove that.