Biochemical composition of tangerine fruits under microfertilizers

The paper presents the long-term research and its results in the field of biochemical composition and mechanical analysis of dwarf tangerine fruits ('Miagava-Vase') growing in the subtropical zone of the Black Sea coast, Krasnodar region. The given results have been obtained after treatments with the following micro fertilizers: H3BO3 (at a concentration of 0.06%), MnSO4 H2O (0.4%), ZnSO4 H2O (0.3%) and CuSO4 H2O (0.06%), an option with foliar water spraying served as a control. It is shown that treatments with copper, zinc and boron significantly (at 2.37 - 3.66 mg.100g-1) increase the amount of vitamin C in fruits compared to the control option. The total amount of sugars in fruits was slightly increased under foliar application of manganese salts. The results show an effect of manganese and zinc to the ratio of total sugars and titratable acids and consequently, on the sugar-acid index value. We found that the content of ascorbic acid in tangerine depends on harvesting term, fruit location on the crown, light level, etc. Equally important is the fact that if storage makes up 3 months the loss of ascorbic acid is not more than 12%. Micro fertilizers had a positive effect on market quality: heavier fruits with thin peel were recorded on options with boric acid and manganese treatments. Treatments with boron and copper sulphate increased juice output from the pulp (74 and 76%, respectively, which is 3 - 7% higher than the control option). A higher dry substance accumulation was observed in the option with foliar application of zinc (13.93%). The despite differences in climatic characteristics of research years and annual adverse periods, foliar feeding with micro fertilizers had a positive effect not only on the accumulation of assimilates in the fruit, but also on the preservation of their presentation. The studies have shown that foliar treatments with micronutrients are promising for tangerine crop, which allowed us to develop guidelines for their use as an agro technical method on dwarf tangerine plantations.