Irrigation scheduling of fruit trees according to water balance provided significant differences between locations. In recent years, water status measurements such as water potential have been suggested as irrigation tools in different fruit trees. The aim of this study was to adjust water potential threshold values previously studied and water application approaches that permit the irrigation scheduling of olive trees based on midday stem water potential. The experiments were performed during three seasons (from 2005 to 2007) in two different locations (Badajoz and Ciudad Real) with different weather and cultural conditions. In both locations, the olive orchards were seven years old at the beginning of the experiment but had significantly different canopy development. In Ciudad Real the canopy shaded area at the beginning of the experiment was 15% and the first crop was harvested in 2003. On the other hand, canopy shaded area of the olive orchard in Badajoz experiment was 40% and the first crop was harvested in 2001. Therefore, we assimilated Ciudad Real orchard as young, while Badajoz was mature. Three different irrigation treatments were compared in both locations: Control treatment with traditional water balance as irrigation scheduling and two treatments in which midday stem water potential (SWP) provided the information about water management. In the midday water stem potential irrigation (WI) the threshold value of SWP was -1.2 MPa before the beginning of the massive pit hardening period and -1.4 after this date. Finally, in the deficit treatment (DI) the threshold value of SWP was -2.0 MPa throughout the season. In WI and DI treatment irrigation was applied when SWP reached the threshold value. No significant differences were found between Control and WI in any of the seasons and locations when water potential, leaf conductance, shoot and fruit growth and yield (fruit and oil) were considered. In both locations, the same SWP value in WI treatment produced similar water application as the Control treatment. In DI treatment, shoot growth was significantly reduced in both locations in all the seasons. The SWP in DI trees was clearly affected in both locations, while leaf conductance was only reduced in the Badajoz experiment. In the Ciudad Real experiment no significant differences were found in fruit growth, whereas differences were found in Badajoz. However, yield was significantly reduced in Ciudad Real, but not in Badajoz. WI treatment was successful for no water stress conditions. On the other hand, DI treatment was a mild water stress treatment which reduced yield only in low covert orchard, but not in the ones with almost maximum canopy shaded area. Our work presents an approach for using midday stem water potential in the irrigation scheduling of olive trees. The experiments were performed in two different locations and during three years, in order to establish the usefulness of this approach. The results support that the threshold values suggested for no water stress conditions are the s...
Recent technological advances have made possible automated irrigation scheduling using decision-support tools. These tools help farmers to make better decisions in the management of their irrigation system, thus increasing yields while preserving water resources. The aim of this study is to evaluate in a commercial plot an automated irrigation system combined with remote-sensing techniques and soil mapping that allows the establishment of regulated deficit irrigation (RDI) strategies. The study was carried out over 3 years (2015–2017) in a commercial hedgerow olive orchard of the variety ‘Arbequina’ located in Alvarado (Extremadura, Spain). An apparent electrical conductivity (ECa) map and a normalized difference vegetation index (NDVI) map were generated to characterize the spatial variability of the plot and classify the zones in homogeneous areas. Then, reference points were selected to monitor the different irrigation sectors. In 2015, the plot was irrigated according to the farmer’s technical criteria throughout the plot. In 2016 and 2017, two different areas of the plot were irrigated applying an RDI strategy, one under expert supervision and the other automatically. The results show that in a heterogeneous plot the use of new technologies can be useful to establish the ideal location for an automatic irrigation system. Furthermore, automatic irrigation scheduling made it possible to establish an RDI strategy recommended by an expert, resulting in the homogenization of production throughout the plot without the need for human intervention.
The main objective of this study was to evaluate the effect of different deficit irrigation treatments (control, regulated deficit irrigation [RDI]-1, RDI-2, and RDI-3) on the phenolic profile of the olive paste and oil content. Irrigation treatments with more stress water led to a considerable increase in the phenolic compounds of olive paste, especially in oleuropein (60.24%), hydroxytyrosol (82%), tyrosol (195%), and verbascoside (223%) compared to control. A significant increase in the content of total flavonoids and phenolic acids was also observed for these samples. In virgin olive oils (VOO) elaborated from the most stressed olive trees (RDI-2 and RDI-3), a noticeable increase in phenolic substances with antioxidant properties (oleuropein, hydroxytyrosol, tyrosol, secoiridoid derivatives, and o-vanillin) was observed. Consequently, water stress conditions improved antioxidant activity of VOO.
Abstract. Identifying spatial patterns of soil and plant properties can be an efficient method for site-specific management in areas with homogeneous characteristics (i.e., management zones, MZs). In this study, the use of soil apparent electrical conductivity (ECa) is proposed as the main information source for evaluating the spatial variability of soil and plant properties when using this variability to determine potential MZs. This study was conducted in a commercial hedgerow olive grove. Spatial distribution maps of the main soil properties and normalized difference vegetation index (NDVI) were generated by regression-kriging in which ECa was used as a secondary variable. According to the results obtained by the validation process, all maps were accurate. Soil and plant properties and ECa were subjected to principal component analysis (PCA). Two MZs were determined using a fuzzy cluster classification. The MZ map was validated using data related to soil samples, yield, and NDVI. Establishing different MZs was useful for adapting the irrigation strategies to the soil conditions of the plot, which resulted in increased productivity of the hedgerow olive grove. Keywords: Fuzzy c-means, Principal components analysis, Regression-kriging, Spatial prediction.
Olive fruits and virgin olive oils from a super‐high‐density olive orchard cv. Arbequina under different irrigation treatments (Control, RDI1, RDI2) were characterized by their pigment profile, CIElab colorimetric coordinates, oxidative stability and antioxidant capacity during the olive seasons 2011 and 2012. The control treatment were irrigated according to the total evapotranspiration of the olive grove (100% ETc), while RDI1 and RDI2 consisted of moderate and severe deficit irrigation, respectively. Olive fruits from severe water deficit irrigation treatment (RDI2) showed a significantly greater concentration of pigments compared to the others. In addition, the ratios a*/chlorophylls and chlorophylls/carotenoids indicated a delayed maturation in these olives. Irrigation treatments significantly affected the yellow component (b*) of the virgin olive oils contained. A reduction of 75% in the water applied (RDI2) produced a strong increase in lutein‐zeaxanthin content (38%) and chlorophyll a (50%), oxidative stability, that ranged from 8.37 h (Control) to 13.23 h (RDI2) and antioxidant activity compared to Control. However, the oil production from RDI2 decreased approximately a 49%.
A non-destructive fluorescence method combined with chemometric algorithms has been developed for discriminating between olive oils. The excitation-emission matrices (EEMs) of two olive oil varieties (Arbosana and Oliana) from two crop seasons, which had undergone two different irrigation treatments (control irrigation strategy and regulated deficit irrigation (RDI)), were recorded. EEMs were analysed using parallel factor analysis (PARAFAC), followed by linear discriminant analysis (LDA) incorporating three PARAFAC components. This analysis was able to discriminate between olive oils according to crop season (100% of predictions in the validation set were correct) and variety (100% of predictions were correct). Moreover, good discrimination (80% of correct predictions) was also achieved when examining olive oils belonging to the same variety but submitted to two different irrigation treatments. Further, the olive oil quality parameters obtained using conventional methods were compared with those obtained using unfolded partial least squares (U-PLS). Good correlation coefficients were obtained for Rancimat hours (r = 0.87), K270 (r = 0.75) and total polyphenol content (r = 0.94).
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