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Leaf analysis is essential for diagnosing nutritional status and guiding fertilizer application. The present study aimed to investigate the appropriate time for leaf sampling and the effect of genotype on olive nutrition. We determined leaf nutrient concentrations of calcium (Ca), iron (Fe), and manganese (Mn) in five Greek (‘Amfissis’, ‘Chondrolia Chalkidikis’, ‘Koroneiki’, ‘Mastoidis’, and ‘Kalamon’) and one Spanish (‘Picual’) variety from May 2019 to April 2020. The concentrations of Ca, Fe, and Mn were significantly affected by genotype and season. The highest concentrations for all nutrients were determined in April, while the lowest were in May, June, and October. Leaf Ca concentration significantly increased progressively from May to September for all the varieties. Leaves of ‘Koroneiki’ had the highest Ca concentration. Iron concentrations were within the sufficiency thresholds for all the varieties during the whole experimental period, and ‘Mastoidis’ showed the highest concentration. Leaf Mn concentration for all the varieties increased from May to September with an instant decrease in June, apart from ‘Amfissis’. The varieties ‘Kalamon’ and ‘Chondrolia Chalkidikis’ were found to be above the Mn sufficiency threshold throughout the year. Variations among season and genotype depict the complexity of nutrient transportation in leaf tissues.

The present study was carried out to evaluate the leaf nutrient status of commercially grown strawberries in Latvia during 2014–2022. The results of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo and B in 200 strawberry leaf samples from different strawberry-producing farms were analysed over three periods: 2014–2016, 2017–2019, and 2020–2022. According to leaf analyses, plant fertilization was only partly well managed by the growers. During the research period, strawberries in Latvia were generally sufficiently supplied with N, P, K, Mg, Fe, Mn, Mo, and B, while the level of Ca, S, Zn, and Cu was considered low. The deficiency of these nutrients was characteristic for more than 50% of the samples. Since Ca, S, Zn, and Cu are essential for berry formation and quality and contribute to stress resistance; their deficiency could be one of the limiting factors for strawberry yield. The significant positive correlations found between nutrients, including deficient ones, confirmed their close relationship in the uptake process and the importance of sufficient supply. The results clearly indicated that fertilization could currently be an issue that limits the strawberry harvest in Latvia, and adequate provisions of Ca, S, Zn, and B should be the main focus.

Background: Hop cultivation requires an abundant quantity of nutrients to reach higher cone yield and quality. The aim of this work was the evaluation of different fertilization plans to obtain an improvement in product quality. Methods: Foliar analysis, anatomical analysis through the use of light microscope and SEM; physiological measurements through atLEAF, Handy PEA and spectrophotometry, were carried out to determine chlorophyll content, carotenoids and photosynthetic efficiency in two periods (t1, t2) for four experimental treatments and a Control (Treat 1, Treat 2, Treat 3, Treat 4, Untreat). Leaf texture (texture analyzer), color (colorimeter), DPPH activity (spectrophotometer), bitter acid content (HPLC-UV) and essential oil yields (steam distillation) and cone yields were measured. Results: Treat 2 showed the best performance: (i) in leaves, in terms of texture, chlorophyll content and color; (ii) in cones, with 6.98% of alpha acids, 1.78% of oil yield and 3.55 kg of fresh cones per plants. Conclusion: The fertilization plans caused alteration in micro and macro elements content in hop leaves and in the composition of hop cones. In our conditions, the best fertilization plan, in terms of cone productivity and quality, was Treat 2, highlighting the value of a customized organic foliar fertilization plan for hop cultivation.

A large number of studies have been conducted on organic carbon (OC) variation in mangrove ecosystems. However, few have examined its relationship with soil quality and stratigraphic condition. Mangrove OC characteristics would be explicitly understood if those two parameters were taken into account. The aim of this study was to examine mangrove OC characteristics qualitatively and quantitatively after distinguishing mangrove OC from other OC. Geological survey revealed that the underground of a mangrove ecosystem was composed of three layers: a top layer of mangrove origin and two underlying sublayers of geologic origin. The underlying sublayers were formed from different materials, as shown by X-ray fluorescence analysis. Despite a large thickness exceeding 700 cm in contrast to the 100 cm thickness of the mangrove mud layer, the sublayers had much lower OC stock. Mangrove mud layer formation started from the time of mangrove colonization, which dated back to between 1330 and 1820 14C years BP, and OC stock in the mangrove mud layer was more than half of the total OC stock in the underground layers, which had been accumulating since 7200 14C years BP. pH and redox potential (Eh) of the surface soils varied depending on vegetation type. In the surface soils, pH correlated to C% (r = −0.66, p < 0.01). C/N ratios varied widely from 3.9 to 34.3, indicating that mangrove OC had various sources. The pH and Eh gradients were important factors affecting the OC stock and the mobility/uptake of chemical elements in the mangrove mud layer. Humic acids extracted from the mangrove mud layer had relatively high aliphatic contents, in contrast with the carboxylic acid rich sublayers, indicating that humification has not yet progressed in mangrove soil.

The aim of this work is to evaluate the relationship between the nutrient concentration in petiole sap and different agronomic and climatic variables for a tomato crop grown in a greenhouse in Mediterranean conditions. In addition, the persistence of the nutrient concentration in petiole sap was investigated with the aim of determining the sampling period that implies the best trade-off nutritional information. The experiment consisted of the selection of 20 sampling points inside the greenhouse. The samples of petiole, fully expanded leaf, and soil solution samples were collected weekly from 86 to 163 days after transplanting. Chloride, NO3−-N, H2PO4−-P, Na+, K+, Ca2+, and Mg2+ concentrations were determined in petiole sap and soil solution obtained by suction cups. Nitrogen, P, K, Cl, and Na concentrations were also determined in leaf. Finally, the petiole sap nutritional diagnosis method is the highest sensitive nutritional diagnosis method which compares soil solution and nutrient leaf content related to yield, and the statistical analysis performed in this research demonstrates that crop evapotranspiration (ETc), vapor pressure deficit (DPV), and leaf area index (LAI) are considered the most significant variables that allow the development of these empirical prediction models regarding nutrient concentration in petiole sap.

Nitrogen concentration in plants is normally determined by expensive and time consuming chemical analyses. As an alternative, chlorophyll meter readings and N-NO3 concentration determination in petiole sap were proposed, but these assays are not always satisfactory. Spectral reflectance values of tomato leaves obtained by visible-near infrared spectrophotometry are reported to be a powerful tool for the diagnosis of plant nutritional status. The aim of the study was to evaluate the possibility and the accuracy of the estimation of tomato leaf nitrogen concentration performed through a rapid, portable and non-destructive system, in comparison with chemical standard analyses, chlorophyll meter readings and N-NO3 concentration in petiole sap. Mean reflectance leaf values were compared to each reference chemical value by partial least squares chemometric multivariate methods. The correlation between predicted values from spectral reflectance analysis and the observed chemical values showed in the independent test highly significant correlation coefficient (r = 0.94). The utilization of the proposed system, increasing efficiency, allows better knowledge of nutritional status of tomato plants, with more detailed and sharp information and on wider areas. More detailed information both in space and time is an essential tool to increase and stabilize crop quality levels and to optimize the nutrient use efficiency.

The present study was carried out to evaluate the leaf nutrient status of commercially grown strawberries in Latvia during 2014-2022. The results of N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo and B in 200 strawberry leaf samples from different strawberry-producing farms were analysed over three periods: 2014-2016, 2017-2019, and 2020-2022. According to leaf analyses, plant fertilization was only partly well managed by the growers. During the research period, strawberries in Latvia were generally sufficiently supplied with N, P, K, Mg, Fe, Mn, Mo, and B, while the level of Ca, S, Zn, and Cu was considered low. The deficiency of these nutrients was characteristic for more than 50% of the samples. Since Ca, S, Zn, and Cu are essential for berry formation and quality and contribute to stress resistance; their deficiency could be one of the limiting factors for strawberry yield. The significant positive correlations found between nutrients, including deficient ones, confirmed their close relationship in the uptake process and the importance of sufficient supply. The results clearly indicated that fertilization could currently be an issue that limits the strawberry harvest in Latvia, and adequate provisions of Ca, S, Zn, and B should be the main focus.