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A greenhouse experiment was conducted, in order to study the effect of nitrogen (N) form (NO 3 − , NH 4 + , urea, NH 4 + + NO 3 − ) and concentration (1, 8 and 16 mM) on growth, mineral nutrition and photosynthetic performance of olive plants ( Olea europaea L., cv. ‘Kalamon’). Our data indicate that when plants at high supply (16 mM) received urea as N source better growth performance was recorded, compared to the cases olive plants received other N forms; however, at low to medium N supply (1 or 8 mM) better plant growth performance observed when they were fertilized with NO 3 − –N. Total N uptake at 16 mM was significantly lower when plants received NO 3 − –N, in comparison to the other N forms. NO 3 − form at 16 mM resulted in lower total uptake of P, Fe, Mn and Zn, compared to the other treatments. On the other hand, NH 4 + -N at high N supply (16 mM) resulted in lower total uptake of Ca and Mg. However, significantly higher K uptake was found when plants were treated with NH 4 + , at high N rate (16 mM). High N supply in the form of NH 4 + -N significantly inhibited net photosynthetic rate (A), although the chlorophyll fluorescence (as an indicator of the function of PSII) did not significantly differ among the N treatments. In conclusion, urea-N proved to be the most appropriate N form for the mineral nutrition of the olive cultivar ‘Kalamon’; thus, it should be preferred as a source of N in olive groves receiving high N fertilizations. [ABSTRACT FROM AUTHOR]

• Olive plants were fertilized with manures or a controlled release fertilizer (CRF). • The highest biomass, macronutrient content and PSII activity were found in the CRF. • Significantly lower photosynthetic rate and stomata opening were recorded in the CRF. • The lowest foliar P, K, Mg, Zn and Cu concentrations were found in the CRF. • The higher macronutrient accumulation in the CRF was owed to the higher biomass. Organic fertilization has been proposed as an alternative method, in the frame of sustainable agriculture, to enhance soil fertility and satisfy the nutritional needs of crops, without the input of chemical fertilizers. A six-month pot experiment, with 3 soil amendments, used as organic fertilizers (cow manure-CM, goat manure-GM, and their mixture, i.e. CM + GM) and a controlled release fertilizer (CRF) was conducted, in order to investigate if the growth, nutrient uptake, photosystem II (PSII) activity, photosynthetic rate and total sugars of Olea europaea L. (cv. 'Koroneiki') plants were influenced by the kind of fertilization. The highest plant biomass, macronutrient content and PSII activity were found in the CRF treatment. In contrast, significantly lower photosynthetic and transpiration rates were recorded in the CRF due to the lower stomatal conductance. Translocated sugars were higher in the CM + GM treatment, while total sugar concentration did not significantly differ among the treatments. Despite the highest content of all macronutrients, Fe and Mn recorded in the CRF, the lowest foliar P, K, Mg, Zn and Cu concentrations revealed that the higher nutrient accumulation, compared to the organic treatments, should be ascribed to the higher plant biomass, rather than to higher nutrient uptake. From the above data, it is clear that the kind of organic/inorganic fertilization significantly influenced soil organic C content, fertility, growth, nutrient uptake and the physiology of olive plants. Thus, the kind of manure(s) used to enhance soil fertility and support crop production should be seriously taken into consideration by the olive growers before its/their use. [ABSTRACT FROM AUTHOR]