Northern Mediterranean region’s vulnerability to climate change has been highlighted by the increased occurrence and intensity of agriculture droughts in recent years. Consequently, there has been an enormous increase in the interest in "deficit irrigation" approach to irrigation, where water supply is reduced below maximum levels and mild stress is allowed with minimal effects on yield. In order to determine the vegetative and productive response of local variety 'Istrska belica' to variable water quantities applied during the extreme drought season, an experiment was set in a 17 year old olive grove located at Slovenian Istria (southwestern Slovenia). Four irrigation treatments were applied during extreme drought growing season, with applied water in the amount of 15% ETc (crop evapotranspiration), 33% ETc, 40% ETc, 100% ETc and rain fed conditions. Irrigation regime significantly affected the shoot length, fruit set, a number of fruit per shoot and olive production. This finding was also confirmed by further ANOVA analysis, which showed a statistically significant difference (shoot growth F (4, 190) = 4.84, P = 0.00095; fruit set F (4, 190) = 2.27, P = 0.06; number of fruit per shoot F (4, 190) = 4.64, P = 0.0134 and crop yield F (4, 35) = 5.02, P = 0.002) between irrigation treatments. Although the rain-fed treatment resulted in the smallest yield, the shoot growth of trees under rain-fed conditions was greater (6.05 cm) than that of trees receiving 15% ETc (4.45 cm), 33% ETc (4.35 cm), 40% ETc (3.39 cm) and 100% ETc (2.10 cm) irrigation treatments. Results showed that flowering was not significantly affected by water supply.
COBISS.SI-ID: 1538805700
In the last years the Slovenian olive growers and producers have faced problems to achieve constant yields and quality of olive oil due to the extreme weather conditions, especially because of the more frequent occurrence of the drought. A technically accomplished pilot automatic irrigation system of olive trees was established. In 2015, the impact of different irrigation treatments (0% ETc (crop evapotranspiration), 15% ETc, 33% ETc, 40% ETc and 100% ETc) on olive variety 'Istrska belica' were studied to determine the minimum amount of added water that has positive effect on the yield and quality of the produced extra virgin olive oil. The study results showed that the quantity of applied water equal to 100% ETc had a significant effect on yield of olive fruits. The average fruit mass of the trees grown under full irrigation (100% ETc) was significantly higher than those given rain-fed and deficit irrigation treatments (15% ETc, 33% ETc, 40% ETc), between no significant differences were found. The fatty acid composition showed the highest amount of oleic acid (75.61%) at 100% ETc and the lowest amount (74.69%) at 15% ETc, while the highest amount of linoleic acid (6.52%) was determined at 15% ETc, the lowest (5.98%) at 100% ETc. Total biophenol content and biophenol compostion was determined. The 40% ETc irrigation system showed the highest amount of total biophenols, total oleuropein and total ligstroside derivatives (1076 mg/kg, 562 mg/kg and 388 mg/kg, respectively), while the lowest results (883 mg/kg, 477 mg/kg and 299 mg/kg, respectively) were determined in control system (0% ETc). The organoleptic assessment of the olive samples showed that the positive sensory attributes of fruity, bitter and pungent were more intensive at 33% ETc and highest graded. Olive oil from non-irrigated trees (0% ETc) received the lowest sensory score.
COBISS.SI-ID: 1538806212
Sugars, the primary metabolites, play an important role in the process of olives ripening, as they provide energy for metabolic changes and serve as a source for the biosynthesis of fatty acids. Phenolic compounds that are known as secondary metabolites can be synthesized in plants as the reflection of stressful situation such as tissue damage and UV rays. The objective of the study was to assess the impact of different irrigation treatments (0% ETc, 15% ETc, 33% ETc, 40% ETc, 100% ETc) on primary metabolites (sugars, sugar alcohols) and secondary metabolites (phenolic compunds). In different phenological periods the levels of oleuropein, sugars and sugar alcohols were determined in olives and leaves sample in the crop years 2014, 2015 and 2016. The levels of oleuropein in olive fruits and leaves were the highest under the irrigation treatment of 40% ETc and decreased importantly under the irrigation treatment of 100% ETc. The median levels of glucose were higher compared to the mannitol and fructose levels in olive fruits. Total determined sugars in olive fruits during the maturation decreased. While in olive fruits the significant correlations were found between the determined sugars and sugar alcohols and different irrigation treatments, we did not observe any correlation between determined sugars and sugar alcohols in olive leaves and irrigation treatments. Our research confirmed the complexity of the oleuropein and sugars or sugar alcohols content in the leaves and fruits of the olive trees from Slovenian Istra that depend on various factors, not just on drought stress. Weaker and not so obvious correlations between the studied compounds and the drought stress might be the consequence of unusual rainfall in the studied crop years.
COBISS.SI-ID: 1538805956