Effect of Foliar Spray of Some Micronutrient Elements before and after Flowering on Quantitative and Qualitative Characteristics of Table Grape cv. Khoshnaw

Table grape (Vitis vinifera L.) is one of the most important small fruits in Iran produced in a wide range of climates from temperate to tropical regions. Khoshnaw cultivar is one of the most important table grapes in Iran. Vineyard soil in many parts of Iran is calcareous, leading to the decrease in the availability of micronutrients and exposure of vines to severe nutritional disorders. Lack of imbalanced fertilization is one of the reasons for the reduction in yield as well as fruit quality of vineyards. Iron, magnesium and zinc are essential nutrients that play an important role in increasing production and product quality. Zinc and iron deficiencies are the most common micronutrient disorders that have been observed in many vineyards of Iran. Other common deficiencies include manganese, boron, copper, and molybdenum. Most vineyards of Boyer Ahmad located in regions, where soil temperature is very low in spring, and obviously under these conditions and just when the grapevines need to make most of the mentioned elements, absorption of nutrients from the soil by the roots is reduced. However, there is high amount of lime (≥ 60%) in the soil of the same area in this condition with high pH (7.9). Therefore, under this situation, vines cannot uptake iron and other micronutrients including zinc and boron. The fertilizer sources and time of their application are two important factors. The aim of this study was to determine the best concentration and application time of Ferozinc fertilizer on the quantitative and qualitative characteristics of table grape cv. khoshnaw.
The experiment was conducted to investigate the effect of foliar application of some micronutrient elements before and after flowering on quantitative and qualitative characteristics of table Grape cv. Khoshnaw in Yasuj during 2012. An experiment was conducted in private vineyards in Chitab district of BoyerAhmad region. The average annual precipitation was 676.7 mm. The minimum and maximum temperatures of this area varied from -7.8 oC to 35.3oC during the year. The average minimum and maximum temperatures in growing season were 13 oC and 29.5oC, respectively. 15-year-old own-rooted vines were trained by using head system. The vines were spaced 2.5 × 3 m. They were pruned by using spur pruning which left about 60 buds on each vine. The experiment was arranged as factorial based on randomized complete block design with two factors and four replications. The first factor included different levels of Ferozinc fertilizer (0, 500, 1000, 1500, and 2000 mg/l) and the second factor included different spraying times (before flowering, after flowering, and both times). The quantitative factors measured were the average of bunch weight, and average of fruit weight per bunch; and qualitative factors were percent of soluble solids (TSS percentage), the reaction of juice (pH), total acidity (TA percentage), TSS/TA ratio and vitamin C, respectively. The data were analyzed using MSTATC package program and means were separated using Duncan's Multiple Range Test at P ≤ 0.05 and P ≤ 0.01.
Results showed that the effects of Ferozinc fertilizer application were significant (p≤0.01) on the average of bunch weight, average of fruit weight per bunch, TSS/TA ratio, pH and vitamin C content. Moreover, the effect of foliar application time on all traits was significant, except for juice pH (p≤0.01). Based on the results of mean comparison, the interaction effect between different levels of Ferozinc fertilizer and times of foliar application on vitamin C content and pH of grape juice were significant (p≤0.01). The highest cluster weight (220.222 gr), average fruit weight per cluster (215.887 gr), TSS/TA ratio (31.29), pH (3.68) and vitamin C (2.849 mg/100 cc fruit juice) were obtained in the treatment containing 1000 mg/l Ferozinc fertilizer and both application times (before and after flowering).
In general, the results of the present study showed that the unavailability of optimal nutritional conditions in control treatment increased the quality of fruits. Therefore when the plant is faced with nutrition abnormalities, moderate consumption of elements could enhance quantity and quality of products. According to the results of this research, application of ferozinc fertilizer at concentration of 1000 ppm before and after flowering is recommended to improve the quantitative and qualitative characteristics of table grape cv. Khoshnaw under irrigation conditions in this area.