Irrigation of Young Olives Grown on Reclaimed Karst Soil Increases Fruit Size, Weight and Oil Yield and Balances the Sensory Oil Profile

Abstract

The influence of different irrigation regimes on olive fruit morphological parameters and on the quantity and quality (marketable indices, phenolic content, fatty acid composition, and sensory profile) of virgin olive oil (VOO) obtained from the Croatian cultivar Oblica, grown on an extremely rocky and dry reclaimed karst soil, was studied over three years. Four treatments were applied: rain-fed and three treatments calculated as 50%, 75%, and 100% of the crop’s irrigation requirement (Irr). Principal component analysis separated growing seasons (GS) that differed in precipitation. In the 2016 season, which had a low number of fruits per kilogram and provided a higher amount of balanced VOO with medium to intense bitterness and pungency (rain-fed treatment), the oil yield increased by irrigation (Irr 75 and Irr 100) up to 18%, while unchanged phenolics, bitterness, and pungency were observed for the VOOs obtained. In the drier GS (2017), which under rain-fed conditions had high fruit per kg, smallest fruit sizes, and lowest oil yield, and in which the VOOs had high phenolic content and intense sensory taste attributes, fruit weight, fruit sizes, and oil yield increased by 35% in all irrigation treatments, while phenols, bitterness, and pungency decreased, balancing the sensory profile of the VOOs. The results obtained here led us to conclude that the irrigation of young olives resulted in a positive effect, with the indication that an abundant water supply is more effective in drought conditions.

Modulation of the Irrigation Practices in Croatia for More Sustainable Olive Growing

“…Almost the same trend was recorded in both years for other measured parameters such as length, width of fruit and stone, pulp mass, and the ratio of pulp mass to stone mass (Table 6). The results were in accordance with other research that found that increasing the amount of irrigation water had a positive effect on the morphological characteristics of the fruit [59][60][61][62]. During drought, the water content in the plant decreases, the cells shrink, and the cell wall relaxes, resulting in a loss of turgor.…”

“…The location also had a significant influence on the characteristics of the fruit, where the values of most observed properties were higher in Novigrad compared to Žman (Table 6). The results were consistent with other studies that showed that increasing the amount of irrigation water has a positive effect on fruit and stone weight [59,62]. Freihat [61] found that irrigation of 40, 60, and 80 L on a weekly basis had a significant effect on the weight of fruits produced by both olive varieties 'Grossa de Spain' and Nabali in both consecutive growing seasons (2014 and 2015).…”

“…The results were similar to those by Pierantozzi et al [60], who found that irrigation had a slight effect on the yield of olive fruit per tree, as also measured by Jukić Špika et al [62] on meliorated karst on the cultivar Oblica. In contrast, Nuzzo et al [67] found differences in yield between irrigated and non-irrigated trees of the Coratina cultivar in the first four years after planting.…”

“…Smaller differences between the irrigated treatments were found in 2020, when a higher amount of precipitation was recorded in July (Figure 1). This finding is supported by Jukić Špika et al [62], who found a greater influence of irrigation in 2017, when a lower amount of precipitation was recorded during the time of stone hardening and intense fruit growth compared to 2016 with higher amounts of precipitation.…”

“…A change in the category of virgin olive oil can affect economic losses for the producer [77]. Jukić Špika et al [62] found a similar trend for the cultivar Oblica grown on reclaimed karst for FFA parameters. Naima FFA had the lowest values in the treatment (Irr 100%), in which the highest amount of irrigation water was added during two years, while in one year, there was no difference between treatments.…”