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The response of olive (Olea europaea) trees to zinc nutrition

Zipori, I., Yermiyahu, U., Tugendhaft, Y., Ben-Gal, A., Dag, A.
Acta horticulturae 2018 no.1199 pp. 351-356
Olea europaea, crops, foliar application, fruit set, leaves, nutrition, olives, soil, soil treatment, surveys, trees, zinc, Israel
Zinc (Zn) is an essential micronutrient in all agricultural crops, with an important role in metabolic as well as fruit-set processes. A survey of 1850 olive trees, carried out in Israel, revealed that, in about 25% of the surveyed trees, leaf Zn concentrations were lower than 10 mg kg-1 DW, considered to be the deficiency threshold in olive. In another 25% of the surveyed population, leaf Zn concentrations were only slightly above the deficiency threshold. In the present study, Zn was applied to the soil as a Zn chelate in three experiments and, in two of them, by foliar application as well. At all experimental sites, initial leaf Zn concentrations were around 10 mg kg-1 DW. Leaf Zn concentrations did not increase or increased up to 30% as a result of soil application, but increased two- to threefold as a result of foliar application. Despite the large increase in leaf Zn concentration, no response was observed with respect to fruit set or yield. This puts into question the effectiveness of foliar application in olives, as well as the current threshold value of 10 mg kg-1 DW.