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Isaac Zipori, Arnon Dag, Yizhar Tugendhaft, and Reuven Birger

Table olives are traditionally harvested manually. However, a shortage of agricultural workers and high labor costs have prompted the search for mechanical solutions. Mechanical harvesting of four cultivars of green table olive—Manzanilla, Hojiblanca, Souri, and Nabali Mouhassan—was compared with manual picking in terms of harvest efficiency and final product quality. Mechanical harvest methods were: trunk shaking with and without simultaneous rod beating and with and without the application of an abscission agent. Olives were immersed in a diluted NaOH solution in the field, transported to the processing plant, and subjected to commercial procedures processing. Application of an abscission agent resulted in inconsistent fruit-detachment force values and did not affect harvest efficiency. Mechanical harvest with rod beating reached high harvest efficiencies of 80% to 95%, whereas the elimination of rod beating significantly reduced harvest efficiency. Final product quality of the mechanically harvested ‘Hojiblanca’, ‘Souri’. and ‘Nabali Mouhassan’ was similar to that of their manually picked counterparts, whereas that of cv. Manzanilla was inferior to those picked manually. High harvest efficiencies can be obtained using trunk shakers and simultaneous rod beating but final product quality of the mechanically harvested olives depends on variety. In some, mechanical harvesting can be used safely; in others such as cv. Manzanilla, further work is required to obtain a good-quality final product.

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Arnon Dag, Smadar Boim, Yulya Sobotin, and Isaac Zipori

Most newly planted olive (Olea europaea L.) orchards are irrigated and harvested mechanically. We assessed the effects of olive storage temperature and duration on the resultant oil’s quality in three cultivars from modern orchards. Oil acidity increased with storage temperature and time, most markedly in ‘Barnea’ and least in ‘Koroneiki’. In ‘Koroneiki’, after 9 days in cool storage (4 and 10 °C), free fatty acid (FFA) level remained constant. Polyphenol (PP) content behaved differently among cultivars: in ‘Picual’, it was relatively invariable; in ‘Barnea’, it decreased moderately; and in ‘Koroneiki’, it decreased sharply to half of its initial value in 4 °C storage and one-sixth its initial value in room temperature storage after 23 days. Peroxide value (PV) did not increase during the storage period and did not appear to be affected by temperature. Thus, different cultivars show different responses to storage, and fruit originated from modern orchards are not necessarily more sensitive to storage than those from traditional orchards.

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Arnon Dag, Ran Erel, Alon Ben-Gal, Isaac Zipori, and Uri Yermiyahu

The global production of olives (Olea europaea L.) has increased rapidly over the last decade as a result of the expansion of orchards with high tree densities. Most olives are propagated from rooted cuttings. The present study evaluated the propagation rate of rooted cuttings as a function of the nutritional status of the stock trees. Rooting ability was evaluated for cuttings taken from container-grown stock plants exposed to eight concentrations of nitrogen (N) (ranging from 0.4 to 14.1 mm), seven concentrations of phosphorus (P) (ranging from 0.01 to 0.62 mm), and five concentrations of potassium (K) (ranging from 0.25 to 5.33 mm). Increases in N level negatively affected rooting rate and cutting survival. Propagation success was increased threefold as N in irrigation water was reduced from the highest to the lowest treatments. Enhanced root development under low N concentrations resulted in higher root weight compared with the high N concentrations. The high concentration of N fertilization negatively affected the propagation rate but was not reflected in N concentration of diagnostic leaves. There was, however, a significant negative correlation between N in twigs and propagation rate. Regarding response to K concentration, no effect was found on rooting rate or cutting survival. Except for reduced rooting at the lowest concentration, P had a negligible effect on rooting rate. The experimental results indicate the need to avoid overfertilization of olive stock trees with N to promote successful propagation.

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Ran Erel, Arnon Dag, Alon Ben-Gal, Amnon Schwartz, and Uri Yermiyahu

The independent effects of nitrogen, phosphorus, and potassium concentrations in the irrigation solution on flowering and fruit set in olive trees (Olea europaea L. cv. Barnea) were studied in a container experiment. Treatments included eight levels of N ranging from 0.4 to 14.1 mm, seven levels of P ranging from 0.01 to 0.62 mm, and seven levels of K ranging from 0.25 to 5.33 mm. At low environmental concentrations of each of the minerals, additions led to large increases in their concentrations in leaves, and as the environmental concentrations became high, relative increases in leaf accumulation were reduced. Availability of N, P, and K was found to influence flowering intensity in the olive trees. Fruit set was affected by N and P, but not K levels. Total fruit load of olives was shown to be a function of flowering level multiplied by fruit set. The final number of olives per tree increased appreciably as leaf P and K increased from minimum levels, and relative increases in fruit load tapered at the highest measured leaf concentrations of the minerals. Maximum fruit load was found corresponding to ≈0.06 mol·kg−1 P and close to 0.35 mol·kg−1 K in leaves. Fruit load increased to a maximum as leaf N increased from 0.7 to 1.3 mol·kg−1 and then decreased as leaf N increased to 1.5 mol·kg−1. The findings indicate that each of the macronutrients plays a fundamental role in processes affecting olive tree productivity.