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Imbalanced Ca/Mg and excess Ni (due to serpentine stress) are limiting factors for plant productivity. The purpose of this study was to investigate if growth, nutrient uptake, PSII activity, photosynthesis and antioxidant activity of pomegranate (Punica granatum L., cv. Granada) plants were affected by serpentine stress. Pomegranate plants were grown in soil substrates from parent material marl (control), serpentine and serpentinized peridotite. Plant height, leaf, stem, root and total plant dry weight, as well as foliar N, P, K, Ca, Zn, Cu, chlorophyll content, fluorescence parameters, photosynthetic rate, and internal water use efficiency (WUEi) were significantly lower for the plants grown in the serpentinized peridotite soil. In contrast, higher ferric reducing antioxidant power (FRAP), total phenolics and total flavonoid content (TFC) levels were found in the serpentinized peridotite soil. The insignificant differences between the marl and serpentine soils in plant growth, PSII activity, photosynthesis and nutrient uptake indicated that P. granatum could tolerate a mild (not with extremely high Ni) serpentine stress. However, P. granatum could not tolerate stress showing excess Mg and imbalanced Ca/Mg, as found for the serpentinized soil of our study. • Soils from marl, serpentine and serpentinized peridotite were used as substrates. • Most foliar nutrients were significantly lower in the serpentinized peridotite soil. • Photosynthesis was significantly lower in the serpentinized peridotite soil. • Chlorophyll and PSII activity were significantly lower in the serpentinized soil. • Increased levels of phenols, TFC and FRAP were found in the serpentinized soil. [ABSTRACT FROM AUTHOR]

Highlights • Soils from marl, serpentine and serpentinized peridotite were used as substrates. • Most foliar nutrients were significantly lower in the serpentinized soil. • Photosynthesis was significantly lower in the serpentinized peridotite soil. • Increased levels of phenols, TFC and FRAP were found in the serpentinized soil. • Differential tolerance to serpentine stress between 'Wonderful' and 'Acco' existed. Abstract It was investigated if differential genotypic tolerance of two pomegranate cultivars ('Wonderful' and 'Acco') to serpentine stress existed. For this purpose, pomegranate plants were grown outdoors, in three soil substrates (from parent material marl, serpentine and serpentinized peridotite). The results indicated that growth, most foliar nutrient concentrations, total chlorophyll content, chlorophyll fluorescence and photosynthetic rate, for both genotypes, were significantly lower in the serpentinized peridotite soil (severe stress). In contrast, higher levels of total phenolics, total flavonoid content (TFC) and FRAP, were found in the serpentinized soil. Lower tolerance index to stress in the serpentinized soil was found for the cultivar 'Acco', than for 'Wonderful'. Overall, the physiological and antioxidant response of 'Acco' was worse, than that of 'Wonderful', under serpentine stress. In conclusion, despite the lower Ni, Cr and Mg accumulation of 'Acco' (compared to 'Wonderful'), its lower tolerance indices in the serpentinized soil probably shows its higher tissue sensibility to serpentine stress. Thus, this genotype should not be preferred for cultivation in soils presenting high degree of serpentinization (excess Mg concentrations). In contrast, from the tolerance indices of both genotypes in the serpentine soil, it is concluded that a mild stress existed in this case. [ABSTRACT FROM AUTHOR]

Leaf and soil samples were taken and analyzed from two mature biological olive groves (Olea europaea L., cv. 'Chondrolia Chalkidikis'), in Thessaloniki, Macedonia, Northern Greece, in order to determine the correlations between soil exchangeable cations and foliar calcium (Ca), magnesium (Mg) and potassium (K) concentrations, and the interrelations among leaf nutrients. Τhe nutritional requirements of trees for both biological groves were exclusively based on patent kali supply and nutrient recycling (via pruning material and weed cut recycling). Foliar K, Ca and Mg were positively correlated with soil exchangeable K, Ca and Mg, in the 40-60 cm layer, then in the 20-40 cm layer. Synergistic uptake mechanisms among Ca2+, Mg2+ and K+ probably exist. Leaf N was negatively correlated with foliar K, and positively with leaf Ca, Mg and manganese (Mn). Foliar P was negatively correlated with leaf Ca, Mg and Mn, while foliar Ca was positively correlated with leaf Mg and Mn. Foliar Mg was positively related with leaf Mn. High phosphorus (P) may decrease leaf Ca, Mg and Mn. Enhanced Ca may increase leaf Mg and Mn, while high Mg may also enhance foliar Mn. Finally, based on the determination of foliar nutrient concentrations, the nutritional requirements of olive trees in Ca, Mg, K, P, Fe, Zn were sufficiently (or over-sufficiently) satisfied. However, additional organic fertilization is needed, in order to achieve optimum levels of N, B and Mn (since their foliar concentrations were slightly insufficient). The correlations between leaf and soil exchangeable Ca, Mg and K, as well as among foliar nutrients should be taken into consideration, in order to achieve successful organic fertilization for mature biological olive groves, and to avoid nutritional imbalances and disorders. [ABSTRACT FROM AUTHOR]

The disposal of olive mill wastewater (OMW) is a serious environmental issue for the Mediterranean countries. However, there is still no common European legislation on the management and the re-use of OMW in agriculture, in the frame of sustainable crop management and the standards for the safe OMW disposal and re-use are left to be set by each EU country, individually. This review paper presents the most effective and sustainable practices for OMW, (treatment, application and management), which can maximize the benefits of OMW on crops and soils, while minimizing the potential hazards for public health, thus promoting environmental sustainability. The findings of this synthetic work suggest that there is enough information and proven sustainable practices to go ahead with the initial formulation of a new consensual framework, environmentally acceptable, socially bearable and economically viable, that could hopefully help to set the standards for the re-use of olive mil wastewater and can lead to a common EU policy on the management and re-use of OMW. [ABSTRACT FROM AUTHOR]

Organic farming has been proposed as an alternative agricultural system to help solve environmental problems, like the sustainable management of soil micronutrients, without inputs of chemical fertilizers. The purposes of this study were: i) to assess Fe, Mn, Zn and Cu bioavailability through the determination of sequentially extracted chemical forms (fractions) and their correlation with foliar micronutrient concentrations in mature organic olive (cv. ‘Chondrolia Chalkidikis’) groves; ii) to determine the soil depth and the available forms (fractions) by which the 4 metals are taken up by olive trees. DTPA extractable (from the soil layers 0–20, 20–40 and 40–60 cm) and foliar micronutrient concentrations were determined in two organic olive groves. Using the Tessier fractionation, five fractions, for all the metals, were found: exchangeable, bound to carbonates (acid–soluble), bound to Fe-Mn oxides (reducible), organic (oxidizable), as well as residual form. Our results indicated that Fe was taken up by the olive trees as organic complex, mainly from the soil layer 40–60 cm. Manganese was taken up from the exchangeable fraction (0–20 cm); Zinc was taken up as organic complex from the layers 0–20 and 40–60 cm, as well as in the exchangeable form from the upper 20 cm. Copper was taken up from the soil layers 0–20 and 40–60 cm as soluble organic complex, and as exchangeable ion from the upper 20 cm. Our data reveal the crucial role of organic matter to sustain metal (Fe, Zn and Cu) uptake -as soluble complexes-by olive trees, in mature organic groves grown on calcareous soils; it is also expected that these data will constitute a thorough insight and useful tool towards a successful nutrient and organic C management for organic olive groves, since no serious nutritional deficiencies were found. [ABSTRACT FROM AUTHOR]

A 6-month field experiment (from October to March) was conducted in a 20-year-old experimental grove of the Aristotle University of Thessaloniki in order to enhance its micronutrient levels and assess the effect of micronutrient foliar application manganese, zinc and boron (Mn, Zn and B) on mineral nutrition, chlorophyll concentration and chlorophyll fluorescence parameters (Fv/Fm, Fv/F0and Performance index, PI) of the olive trees (cv. “Chondrolia Chalkidikis”). The experiment consisted of four treatments (Control-C: trees sprayed with deionized water, T50: trees sprayed with 50 mg/L Mn, Zn and B, T100: trees sprayed with 100 mg/L Mn, Zn and B, T200: trees sprayed with 200 mg/L Mn, Zn and B); the three micronutrients were applied in the forms of manganese sulfate (MnSO4), zinc sulfate (ZnSO4) and boric acid (H3BO3), respectively. The results showed that the most effective treatment for the enhancement of foliar Mn and B levels was T200, while for the increase of Zn levels was T100. In addition, significant differences among the treatments were recorded for most leaf nutrient concentrations (with the exception of potassium (K), which was not influenced by foliar treatment, the other macronutrients, such as calcium (Ca), magnesium (Mg), phosphorus (P) and nitrogen (N), as well as iron (Fe), obtained their maximum concentrations, at the end of the experiment, in C or T50 treatment). Chlorophyll concentrations were not influenced by foliar treatment. Concerning chlorophyll fluorescence parameters (Fv/Fm, Fv/F0and P index), significantly lower values were found in the control (C) trees, compared to the other three treatments, so it seems that a chlorophyll fluorescence technique may be used to detect micronutrient deficiencies in olive groves. However, from all the leaf nutrient concentrations determined, it was found that with the exceptions of: 1) Mn concentrations in the C, T50 and T100 treatments, which were marginal, or slightly deficient; 2) B and Zn concentrations in the C and T50 treatments, which were slightly deficient and marginal, respectively; 3) some K concentrations during the early spring period, which were slightly deficient, all the other concentrations were within the normal levels of sufficiency or within the optimum range, so no serious nutrient deficiency was detected. [ABSTRACT FROM PUBLISHER]

Every year, worldwide olive oil production produces in a short period of time (late autumn-winter) vast quantities of olive mill wastewater (OMW). This product causes environmental and management problems due to its disposal into rivers and lakes. During the last years, OMW application (used either as crude, raw material, or as treated- with different methods- product, in order to decrease its phytotoxicity) was tested under field conditions as organic amendment; many times, the results with regard to the raise of plant growth, crop yields and enhancement of soil fertility were promising, while in some other cases phytotoxicity problems, groundwater contamination, decreased soil porosity, as well as enhanced electrical conductivity, salinity, increased soil acidity and decreased N mineralization rate occurred. On the other hand, OMW is a low-cost source of nutrients (especially N, P, K, Mg and Fe), water, and organic matter; thus, it can be successfully used for the restoration of degraded croplands, in hilly, eroded, poor in organic C, and/or semi-arid areas. Since one of the first steps in land restoration process is the enhancement of soil organic C, OMW is an excellent alternative solution for the: i) increase of organic matter, ii) improvement of soil physical properties, and iii) enhancement of productivity of degraded croplands. In addition, under certain conditions (use of treated, or diluted with water OMW in order to decrease phenol content, avoidance of exaggerate applications, suitable application rate(s) and season), OMW can be safely used as a soil amendment and low-cost organic fertilizer for crops, managed with sustainable systems. The basic purpose of this review was to present and thoroughly discuss all the beneficial aspects of OMW application with regard to: i) the restoration of degraded croplands, ii) sustainable crop management, based on the most important and recently published papers. In addition, the environmental consequences of exaggerate and untreated OMW applications, together with some solutions (strategies) adopted for eliminating soil and groundwater contamination and phytotoxicity are also presented in this review article. [ABSTRACT FROM AUTHOR]

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]

Nutrient availability affects root growth. The effect of potassium (K) level on the root growth, weight, and elongation, as well as on nutrient content of the olive genotypes “Megaritiki,” “wild” olive, “Chondrolia Chalkidikis,” “Biancolilla,” and K utilization efficiency was investigated. For this purpose, a greenhouse experiment was carried out in the farm of the Aristotle University of Thessaloniki. Three treatments were used: T1, that is, 25% modified Hoagland nutrient solution without K in distilled water, T2: 25% modified Hoagland nutrient solution with 0.2 mM K in distilled water, and T3: 25% modified Hoagland nutrient solution with 1.5 mM K in distilled water. K concentration had no significant effect on root growth of olive genotypes. The maximum root elongation was observed in the “wild olive,” in the T3 treatment, and the minimum in “Biancolilla,” in the T1 treatment. K utilization efficiency significantly differed between K treatments for the same genotype, as well as among genotypes for the same K treatment, following the order: Megaritiki > wild olive > Chondrolia Chalkidikis > Biancolilla. Finally, significant differences were found with regard to the effect of K treatment and olive genotype on many macronutrient and micronutrient concentrations in leaves and roots. [ABSTRACT FROM AUTHOR]

Two sustainable management models were studied, in order to investigate if they were successful in satisfying the nutritional needs of mature olive groves (20 year-old olive trees- Olea europaea , cv. ‘Koroneiki’), situated in two geographical regions of Greece (Thessaloniki, Central Macedonia, Northern Greece, and Corfu, Ionian Islands, Western Greece). Nutrient supply in both olive orchards was based, during the last 20 years, on pruning material recycling, as well as on cow manure (8 t/ha/year, in the grove of Corfu) and patent kali (5 kg/tree/year, in the grove of Thessaloniki) application. Soil analysis revealed that pH was slightly alkaline in the olive grove of Thessaloniki and acidic (6.00–6.34) in the olive orchard of Corfu; organic matter content was approximately two times greater in the grove of Corfu. Exchangeable Ca concentrations in deeper soil layers (20–40 and 40–60 cm) of the olive orchard of Thessaloniki were approximately two times greater, compared to those found in the grove of Corfu. In contrast, 2–14.5 times greater K exchangeable concentrations, but only in deeper layers (20–40 and 40–60 cm), were found in the grove of Corfu. DTPA extractable Fe, Mn and Zn concentrations were 9–14, 3–5, and 3–5.5 times greater (depending on soil layer) in the olive orchard of Corfu, compared to those found in Thessaloniki. Leaf K concentrations were significantly greater in the grove of Corfu (1.2–1.4% d.w.), while Fe concentrations in the same olive orchard exceeded 120 ppm. Generally, most of the leaf nutrient concentrations for both groves were within the normal levels of sufficiency, or within the over-sufficiency range (e.g. those of N and K in the grove of Corfu, and P in both olive orchards). Only leaf B concentrations in January (17–19 p.p.m.), in both orchards, and leaf Mn levels in the grove of Corfu were slightly (but not seriously) deficient to marginal. Consequently, it can be concluded that both studied sustainable management models for mature olive groves (no soil tillage, pruning material and weed cuts recycling, in addition to: (i) patent kali, or (ii) manure supply) were successful. Thus, the two models are commercially and environmentally sustainable for olive cultivation, especially in marginal, degraded, and/or hilly Mediterranean areas. Finally, they are of great socioeconomic importance in specific rural areas (where olive-growers combine olive oil production with domestic animal breeding). [ABSTRACT FROM AUTHOR]

Deforestation was, for many years, a common practice in Greece in order for the old forest sites to be used as croplands. These deforestations had a very negative influence on soil fertility, especially in the cases where soil depth was restricted, and very sharp inclinations occurred. All these cases were followed by increase of soil surface runoff and extended soil erosion. The continuously decreased crop yields led very often to the abandonment of cultivation. In order to restore such areas and to enhance agricultural development, different rules from the European Agricultural Fund for Rural Development (EAFRD), in the frame of axis 4 “Forestation of Agricultural Lands” were applied. For the study of the influence of restoration on soil fertility, a research project was performed in the whole community area of Gomati (Chalkidiki, Macedonia, Northern Greece), and soil chemical properties have been determined in: i) degraded agricultural sites, ii) restored with Robinia pseudoacacia (black locust) lands, as well as: iii) in mixed native forests. The results showed that the restoration of the degraded agricultural lands with R. pseudoacacia , 20 years after the establishment of these plantations, led to 1.3–3 times greater (depending on soil layer) organic matter content, 1.2–2.5 times greater N quantity, and in many cases to significantly higher P and K concentrations, compared to the degraded agricultural lands and to the native forest areas, respectively. The highest exchangeable Ca and Na concentrations were recorded in the mixed native forest soils, while the highest DTPA extractable Fe and Mn concentrations were found in the degraded agricultural soils, compared to the other two land use types. Finally, most leaf nutrient concentrations in black locust plantations were adequate to optimum for plant growth and nutrition, with the exceptions of those of K, Cu and Fe, which were deficient, critical and excessive, respectively. [ABSTRACT FROM AUTHOR]

One-year-old self-rooted cuttings of three Citrus limon cultivars (Nouvel Athos, Lisbon, Maglini) were grown in 1 L black plastic bags, containing a mixture of sand: perlite (1:1), in order to investigate: i) if genotypic differences to salt stress existed, ii) if KNO 3 can alleviate salinity stress, iii) the role of carbohydrates (such as the sugars fructose, glucose and sucrose) and proline as possible osmoregulators in C. limon osmoprotection, and iv) if genotypic differences to salt stress tolerance exist among the 3 studied cultivars. The experiment included 3 treatments: i) control (C), i.e. 25% modified Hoagland (No2) solution (MHS)-NaCl, ii) T1, 25% MHS+80 mM NaCl, iii) T2, 25% MHS+80 mM NaCl+5 mM KNO 3 . Plant growth was negatively affected by high NaCl (T1); the highest Cl and Na quantities have been absorbed by Lisbon, while the lowest ones by Maglini. Salt stress reduced macronutrient and Zn concentrations, as well as the total carbohydrate concentration, and increased peroxidase (POD) activity and chlorophyll fluorescence in the leaves of the 3 C. limon cultivars studied; five mM KNO 3 application alleviated the harmful effect of salt stress on leaf total carbohydrate concentration and leaf N and K concentrations. Sucrose was dramatically reduced in all the three genotypes studied, while leaf fructose concentration was significantly increased in Nouvel Nouvel Nouvel Athos and Maglini under salt stress. Leaf proline concentration of Maglini was significantly decreased by the high NaCl concentration, while Nouvel Athos and Lisbon had high proline concentration in their leaves. In conclusion, from the significantly decreased levels of proline for Maglini, together with the greatest reduction of the ratio F v /F m and the least enhancement of POD activity-compared to the other two cultivars-it can be concluded that Maglini was more susceptible to salinity, and should not be preferred for cultivation under NaCl stress. Finally, rich KNO 3 application alleviated the harmful effect of NaCl stress, thus it is highly recommended for use by the growers in areas with salt problems. [ABSTRACT FROM AUTHOR]

Juglans regia, Robinia pseudoacacia, Eucalyptus sp. and Populus sp. plantations, suffering from Mn and Cu toxicity, were limed in order to reduce Cu and Mn solubility in soil. The purposes of the present work were: i) to study the changes in soil chemical properties after the addition of CaCO 3 , ii) to investigate the influence of liming on the reduction of Mn and Cu toxicity. After the addition of CaCO 3 (three applications, during three successive years), pH and CaCO 3 content were significantly increased, while organic C and N were significantly reduced. Exchangeable Ca concentrations have been slightly, or significantly, increased, while those of Mg have been decreased; in addition, ratios Ca/Mg and C/N have been significantly increased after liming. Impressive reductions of DTPA extractable Cu and Mn concentrations (more than 10 times in most cases) were recorded. It was also found that trees without Mn and Cu toxicity symptoms (healthy tress) before liming did not have, in many cases, significantly greater leaf Mn, Cu and Fe concentrations, than trees after soil liming (all the trees were healthy). This probably happened because excess Mn and Cu quantities had been accumulated into their root system. Finally, leaf Mn, Cu and Zn concentrations of trees suffering from toxicity were significantly decreased after soil liming, while leaf Fe concentrations, in all the plant species studied, were increased. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to compare the ability of three micronutrient soil-test extractants [diethylenetriaminepentaacetic acid (DTPA), Mehlich 3, and Soltanpour and Schwab] to determine plant-available concentrations of manganese (Mn), iron (Fe), and zinc (Zn) in three soils (from parent material Marl, Gneiss schist, and Peridotite) from central Macedonia, northern Greece. In black plastic bags containing 3 kg of air-dried soil, self-rooted olive plants (cv. Chondrolia Chalkidikis) were grown for about 5 months and irrigated with distilled water during the experimental period. At the end of the experimental period, the three extractants were evaluated, based on correlation analysis among leaf micronutrient concentrations, total plant micronutrient content of olive plants, and soil micronutrient concentrations determined by each extractant. The largest extractable concentrations of Mn, Fe, and Zn were determined by Mehlich 3, compared to the other two soil-test extractants. However, for the correlation analysis, the greatest correlation coefficient between leaf Mn (and total plant Mn content) and soil extractable Mn was achieved when DTPA was used (varying from 0.76 to 0.88, depending on soil type). Therefore, it is concluded that DTPA was a better extractant to determine plant-available Mn than the other extractants for the three soils studied. For correlations between leaf Fe and Zn concentrations and also for total plant Fe and Zn content, and soil extractable concentrations, the type of extractant and soil type play a very important role in determining the best correlation. This means that in each soil type the greatest correlation was achieved with the use of other extractant. For example, for Fe in the Marl and Peridotite soils the best correlation was found for Mehlich 3, whereas in the Gneiss schist the best correlation was achieved for DTPA (R = 0.72–0.94). For Zn, in the Gneiss schist soil the best extractant in determining plant available concentration was Soltanpour and Schwab (R = 0.49–0.60), whereas in the other two soil types DTPA was found to be the most reliable extractant (R = 0.51–0.78). Therefore, soil type should be carefully and thoroughly studied by the researchers in similar future experiments. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Significantly greater KUE values were found in the T3 and T4 treatments. [•] ‘Koroneiki’ was the most K-efficient cultivar in the T3 and T4 treatments. [•] K concentration affected the plant growth of ‘Kalamon’ and ‘Arbequina’. [•] Greater stomata opening were recorded in the highest (T4) treatment. [•] The photosynthetic rate of ‘Koroneiki’ was not higher in the T4 treatment. [ABSTRACT FROM AUTHOR]

The response of three-month-old rooted cuttings of the olive cultivars ‘Picual’ and ‘Koroneiki’ grown in black plastic bags containing perlite as a substrate to excess manganese (Mn) (640 μM) was studied. The rooted cuttings were irrigated with 50% modified Hoagland nutrient solution. At the end of the experimental period, which lasted 130 days, the total fresh and dry weights, as well as the shoot elongation of ‘Picual’ plants were significantly reduced under excess Mn (640 μM), compared to the control plants (2 μM), whereas the growth of ‘Koroneiki’ plants was similar in both Mn treatments. The tolerance index, which is derived from the ratios between the plant growth data of different treatments and the control one, of ‘Picual’ plants to excess Mn was about half of this of ‘Koroneiki’ plants. In both cultivars, the concentrations of Mn in various plant parts (root, basal stem, top stem, basal leaves, top leaves) were significantly increased as Mn concentration in the nutrient solution increased. Furthermore, in the 640 μM Mn treatment, 2 to 2.5-fold greater Mn concentrations were recorded in almost all plant parts of ‘Koroneiki’, than those of ‘Picual’. Similar results were recorded with regard to the total Mn content per plant (‘Koroneiki’ absorbed much more Mn from the nutrient solution than ‘Picual’). On the other hand, excess Mn negatively affected the absorption of iron (Fe), calcium (Ca), magnesium (Mg), phosphorus (P), zinc (Zn), and boron (B), depending on the olive cultivar. In both cultivars, while the Mn use efficiency was significantly decreased under excess Mn conditions, the nutrient use efficiencies of P, Ca, and Fe were significantly increased, compared to the control plants (2 μM Mn). It was also found that excess Mn resulted in a significant increase of stomatal conductance and transpiration rate of both cultivars, whereas the photosynthetic rate was significantly increased only in ‘Koroneiki’. In ‘Picual’, similar photosynthetic rates were recorded in both Mn treatments. The measurement of the various chlorophyll fluorescence parameters, Fv/Fm and Fv/F0 ratios, revealed that the functional integrity of photosystem II (PSII) of photosynthesis was not affected due to excess Mn, irrespectively of the cultivar. In conclusion, although ‘Koroneiki’ tissues had much higher Mn concentrations than those of ‘Picual’, the parameters related to the growth and photosynthetic performance of plants indicates that the internal tolerance of ‘Koroneiki’ tissues to excess Mn was higher than this of ‘Picual’. [ABSTRACT FROM AUTHOR]

• A P-fertilization experiment (+P or –P) was conducted in two olive groves. • P fertilization influenced soil properties, P fractions and its mineralization. • Acid and alkaline phosphatase activities were significantly higher in the –P plots. • P fertilization did not significantly influence trees' foliar P nutrition. • It is useless for the olive growers to provide P every year in their groves. Often, from soil and plant tissue analyses, over-sufficient foliar P levels in olive trees, grown under low Olsen P availability, are determined. In order to deepen our knowledge in this topic, a field P fertilization experiment (with or without supply of the fertilizer 0-46-0) with 25-year-old olive trees was conducted, in order to investigate if: i) soil organic P was a sufficient 'pool' to satisfy the P nutritional needs of mature, fully productive, olive trees under low Olsen P availability and sufficient organic matter content, ii) the activities of acid and alkaline phosphatase were enhanced under low Olsen P availability, iii) soil chemical properties were significantly influenced by P fertilization, iv) significant differences in foliar nutrition of olive trees existed between P-fertilized (+P) and unfertilized (-P) trees. Our results indicated that in the -P plots 48 % of the total soil P was in organic fraction, while in the + P ones approximately 23 % of the total P was in organic form. In contrast, Olsen, inorganic and total P fractions were significantly higher in the + P plots. In addition, in the + P plots significantly lower: i) soil Fe, Mn and Zn, and ii) foliar Ca, Mg and Mn concentrations were determined, while, in contrast, iii) higher leaf K concentration was found. Foliar P was not influenced by P fertilization, while at the same time, both the activities of alkaline and acid phosphatase were significantly higher in the –P plots, compared to those received P fertilization. Overall, the kind of management of olive groves (sufficient organic matter levels, with or without inorganic P fertilization inputs) significantly influences P dynamics and modifies its fractions in soils, while it also affects organic P mineralization and supports P nutrition for olive trees. It is believed that these data reveal the crucial role of organic matter to sustain P uptake and contribute towards a sustainable management of olive groves to support and sufficiently satisfy the P nutritional needs of olive trees, by also significantly reducing the unnecessary annual P fertilizer inputs. [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]

• Pomegranate cultivar (cv.) 'Grenada' was the most susceptible under all saline conditions. • Pomegranate cvs. 'Wonderful' and 'Ermioni' may be cultivated under saline conditions. • Concentrations of Ca and Mg in leaves significantly reduced under KCl and K 2 SO 4 salts. • The highest concentrations of KCl and K 2 SO 4 (75 mM) decreased the chlorophyll concentration. The present investigation assesses the behavior of three pomegranate cultivars (Punica granatum L.) ('Wonderful', 'Ermioni' and 'Grenada') under increased concentrations of three salts (NaCl, KCl and K 2 SO 4) after 150 days of growth in vivo conditions. The aim of this research was to study the nutrient accumulation and distribution in leaves and roots and its effects on total chlorophyll (a + b), carotenoids, photosynthetic rate and stomatal conductance of leaves. In general, high salt supply of KCl and K 2 SO 4 led to significant decline in Ca and Mg concentration in leaves in all cultivars. 'Grenada' found with the highest concentration of Mn in leaves under all salt treatments. Regarding the roots, 'Wonderful' had the highest Mg concentration at 25, 50 and 75 mM of KCl and K 2 SO 4 , while 'Ermioni' had the maximum Ca concentration in roots. Chlorophyll concentration was reduced by the effect of KCl and K 2 SO 4 salts in all cultivars. Furthermore, K 2 SO 4 salt significantly reduced carotenoid concentration in leaves in all cultivars, especially 'Wonderful' showed 63.36 % reduction. 'Grenada' had the lowest photosynthetic rate and K 2 SO 4 salt exerted a significant effect in all cultivars. Regarding stomatal conductance, 'Ermioni' had the highest values with KCl and K 2 SO 4 salt treatments, while 'Grenada' was the most affected cultivar by all salts and at all concentrations. Our findings show the considerable potential of exploiting saline soils to obtain pomegranate plants with higher level of salt tolerance. Furthermore, our results suggest that 'Wonderful' and 'Ermioni' pomegranate cultivars may be cultivated also under marginal saline conditions. [ABSTRACT FROM AUTHOR]