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Maximizing nitrogen uptake efficiency is a sustainable objective to reduce the amount of nitrogen fertilizers applied in olive orchards. Many factors affect this parameter, but nothing is known about whether there are differences among cultivars related to nitrogen uptake efficiency in the olive, and if there are interactions with soil type. To clarify these questions, two groups of experiments were conducted. In the first group, four experiments were carried out in which 20 olive cultivars were compared. In the second group, three experiments were carried out to study the interaction with the type of soil. In all experiments, mist-rooted olive cuttings were growing in 1.1 L pots containing a mixture of sand and peat (2:1 by volume). Depending on the experiment, plants were placed in a shadehouse or in growth chambers at 25/15 °C (day/night) with a 14 h photoperiod and 70% humidity. Plants received weekly applications of 100 ppm N throughout the irrigation water, alternating with one or two applications of 150 mL of tap water. Some plants of each cultivar did not receive nitrogen and served as a control for NUE calculation. A nutrient solution without nitrogen was applied every four weeks to prevent nutritional deficiencies. Results indicated that there are differences among cultivars in the efficiency of uptake nitrogen. The Spanish cultivars ‘Picual’, ‘Arbequina’ and ‘Manzanilla de Sevilla’, together with the Greek cultivar ‘Koroneiki’ and the Italian ‘Frantoio’, were the cultivars with high NUE in this work. Soil type did not affect NUE, and no interaction between soil type and cultivar was observed. [ABSTRACT FROM AUTHOR]

Maximizing nitrogen uptake efficiency is a sustainable objective to reduce the amount of nitrogen fertilizers applied in olive orchards. Many factors affect this parameter, but nothing is known about whether there are differences among cultivars related to nitrogen uptake efficiency in the olive, and if there are interactions with soil type. To clarify these questions, two groups of experiments were conducted. In the first group, four experiments were carried out in which 20 olive cultivars were compared. In the second group, three experiments were carried out to study the interaction with the type of soil. In all experiments, mist-rooted olive cuttings were growing in 1.1 L pots containing a mixture of sand and peat (2:1 by volume). Depending on the experiment, plants were placed in a shadehouse or in growth chambers at 25/15 °C (day/night) with a 14 h photoperiod and 70% humidity. Plants received weekly applications of 100 ppm N throughout the irrigation water, alternating with one or two applications of 150 mL of tap water. Some plants of each cultivar did not receive nitrogen and served as a control for NUE calculation. A nutrient solution without nitrogen was applied every four weeks to prevent nutritional deficiencies. Results indicated that there are differences among cultivars in the efficiency of uptake nitrogen. The Spanish cultivars ‘Picual’, ‘Arbequina’ and ‘Manzanilla de Sevilla’, together with the Greek cultivar ‘Koroneiki’ and the Italian ‘Frantoio’, were the cultivars with high NUE in this work. Soil type did not affect NUE, and no interaction between soil type and cultivar was observed.

Highlights: [•] Nitrogen uptake efficiency (NUE) exponentially decreases with the amount of N applied. [•] The method of nitrogen application, foliar or to the soil, does not affect nitrogen uptake. [•] Nitrogen status of olive plants affects nitrogen uptake efficiency. [•] Systematic applications of large amounts of fertilizer N may cause over-fertilization and negative effects in the plant and the environment. [ABSTRACT FROM AUTHOR]