Migdal Ha‘Emeq, Israel
Migdal Ha‘Emeq, Israel

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Dag A.,Israel Agricultural Research Organization | Naor A.,Golan Research Institute | Ben-Gal A.,Israel Agricultural Research Organization | Harlev G.,Israel Agricultural Research Organization | And 7 more authors.
Journal of the Science of Food and Agriculture | Year: 2015

BACKGROUND: Over the last two decades, the area of cultivated super-high-density olive orchards has increased rapidly. Water stress is an important tool in super-high-density orchards to reduce tree growth and promote suitability for overhead mechanical harvesters. Little is known regarding the effect of water stress in super-high-density orchards on oil quality parameters. In this study the effect of irrigation rate on oil quality parameters was evaluated in a six-year-old super-high-density 'Koreneiki' olive orchard for five consecutive seasons. Five water status levels, determined by irrigating in order to maintain various midday stem water potential threshold values (-1.5, -2, -2.5, -3 and -4 MPa), were applied during the oil accumulation stage. RESULTS: The MUFA/PUFA ratio and free fatty acid content generally decreased as a function of increasing tree water stress. In most seasons a reduction in polyphenols was found with decreasing irrigation level. Peroxide value was not affected by the water stress level. CONCLUSION: The present study demonstrates that limiting irrigation and exposure of olive trees to water stress in a super-high-density orchard lowers free fatty acid content and therefore benefits oil quality. However, the decreased MUFA/PUFA ratio and the reduction in polyphenol content that were also found under increased water stress negatively influence oil quality. © 2014 Society of Chemical Industry.

Naor A.,Golan Research Institute | Schneider D.,Galilee Technology Center | Ben-Gal A.,Israel Agricultural Research Organization | Zipori I.,Israel Agricultural Research Organization | And 5 more authors.
Irrigation Science | Year: 2013

The interactions between irrigation rates applied during the oil accumulation stage and crop load were studied in a six-year-old very-high-density Koroneiki (Olea europaea L.) orchard. Five irrigation rates, determined as thresholds of midday stem water potential, were applied from July 1st until harvest in 2008 and 2009 and from July 1st to the end of September in 2010. Oil yield increased with increasing crop load in all the irrigation treatments. Oil yield did not respond to increasing irrigation at very low crop load and the higher the crop load the higher the response to irrigation. There was no response to irrigation at the lowest crop loads, but the higher the irrigation rate the higher the oil yield at high crop loads. The predicted commercial oil yield at common fruit counts increased from 1.99 t/ha at the lowest irrigation rate to 3.06 t/ha at the highest irrigation rate. Stomatal conductance decreased with decreasing stem water potential but leveled off at 30-60 mmol m-2 s-1 at stem water potential values lower than -4.0 MPa. High crop load increased stomatal conductance and decreased stem water potential relative to low crop load at low and medium irrigation rates. The effect of crop load on water relations became evident by the end of August and was well pronounced at the beginning of October. Physiological and irrigation water management implications related to the interactions between tree water status and crop load are discussed. © 2012 Springer-Verlag.

Schneider D.,Galilee Technology Center | Goldway M.,Galilee Technology Center | Birger R.,Agriculture Valley Center | Stern R.A.,Galilee Technology Center
Scientia Horticulturae | Year: 2012

High-density olive orchards (1000-3000treesha-1) allow use of the continuous straddle harvester that rides over the tree canopy, with very low harvesting and labor costs. However, tree size must be controlled, so that the harvesting machine can pass over the hedgerow and light can penetrate the tree canopy. To achieve this, high-density planted 'Koroneiki' olive trees, aged 5-8 years, were soil-treated with the gibberellin-biosynthesis inhibitor uniconazole at 0.1 or 0.2g per tree for four consecutive years (2007-2010) to reduce their growth rate. Uniconazole reduced 2007-2010 trunk cross-sectional area increment, 2009-2010 accumulated pruned branch weight, tree height and overall tree size. However, the treatment failed to affect the number of new leaves developed on a shoot, and shoot elongation was not consistently inhibited. Nevertheless, a higher leaf density was found for trees treated with 0.2g uniconazole per tree starting from the second year of the experiment and newly growing shoots on treated trees exhibited weeping-type growth. As a result, the architecture of the treated trees was changed, with the development of very thick and dense foliage. Cumulative fruit and oil yields for 2007-2010 were reduced in the uniconazole-treated trees, significantly so for the 0.2g per tree treatment. It was postulated that productivity reduction is a consequence of the altered 'Koroneiki' olive tree architecture, which decreases light interception in the tree canopy. Thus, although the results demonstrate that soil application of uniconazole can be used to control olive tree size in high-density orchards, it should be used carefully to ensure adequate tree illumination, so as to avoid crop loss. © 2012 Elsevier B.V.

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