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BACKGROUND: The natural abundance of stable isotope 15N (δ15N) in production systems has emerged as an alternative to distinguish organic products from conventional ones. This study evaluated the use of δ15N values recorded for nitrogen fertilizers, soil and plant tissue in order to set the differences between organic and conventional agricultural production systems applied to rice, potatoes, apple and banana crops. RESULTS: Values of δ15N recorded for N sources ranged from +5.58‰ to +18.27‰ and from −3.55‰ to +3.19‰ in organic and synthetic fertilizers, respectively. Values recorded for δ15N in food from organic rice, potatoes and banana farms were higher than values recorded for δ15N in conventional farms; the same was observed for values recorded for δ15N in leaves from the four crops. CONCLUSION: Results have allowed for differentiation between production systems due to values of δ15N recorded in leaves of all crops and food, for rice, potatoes and banana trees. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND Feijoa [Acca sellowiana (Berg) Burret] is a Brazilian native fruit with few commercial‐level plantations and high agroindustrial potential. A genotype evaluation experiment was conducted from 1996 onward, aiming to obtain fruits based on the agronomical parameters; however, the selection based on chemical composition had not been evaluated with respect to developing a new cultivar. Accordingly, the present study aimed to discriminate seven accessions of feijoa in terms of nutritional composition, phenolic compounds and antioxidant activity using multivariate analysis (principal component analysis and multivariate contrast), targeting the potential production of a new cultivar with better nutritional value and high antioxidant capacity. RESULTS: Feijoa husk presented high content of ashes, lipids, proteins, carbohydrates, phenolic compounds and antioxidant activity compared to feijoa pulp. However, only feijoa pulp was selected to multivariate analysis because it is the fruit edible part. Data variability was explained in 78% and the feijoa pulp accessions were discriminated into four groups related to their characteristics. The accession 5 discrimination can be explained by the high content of ashes, carbohydrates, soluble solids, phenolic compounds and antioxidant activity. Accession 6 was also discriminated by the high content of total acidity, pH and proteins, as well as a low content of soluble solids. CONCLUSION: Feijoa accessions may be indicated for increasing plant selection via hybridization with the other accessions, aiming to produce new cultivars with better nutritional composition and antioxidant capacity. For example, accession 5 is the most suited fruit for human consumption and is a potential plant with respect to becoming a new cultivar. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Potassium (K) nutrient existent in the soil does not always supply pear tree (Pyrus communis L.) demand, which makes the use of potassium‐based fertilizer necessary. The objective of this study was to evaluate the impact of potassium fertilization on yield and pears quality in order to establish critical K levels in soil and leaves. The treatments consisted of K application rates of control, 40, 80, 120 and 160 kg K2O ha−1 yr−1 during four crops (2013 to 2017). The fruit quantity, mass and yield were evaluated, and leaves were collected for nutrient analysis. Stratified soil samples were collected, prepared and subjected to exchangeable K extraction by Mehlich‐1. In the last two crops, peel color, ethylene production, and respiratory rate were also evaluated after 90 days inside a controlled atmosphere storage chamber. After storage, pears were submitted to a shelf life of 7 days to evaluate the epidermis color, ethylene production, respiratory rate, total titratable acidity (TTA), soluble solids (SS), and pulp firmness. Potassium fertilization increased the exchangeable K contents in the soil, but it was not always correlated with an increase of K concentration in the leaves and fruit. The most economical dose was 45.40 kg K2O ha−1 in the 2016/2017 crop season. It was not possible to estimate K critical levels in the soil and leaves. The fruits submitted to higher doses of K showed the lowest values of ethylene production and respiration rate, which resulted in an increase in storage life in cold rooms and on the shelves. [ABSTRACT FROM AUTHOR]

Core Ideas: Feijoa fruit combine unique flavor and medicinal properties.The Brazilian feijoa collection exhibit high variability in fruit traits.Years was the major effect to all fruit trait phenotype in south of Brazil. The aim of the present work was to physicochemically characterize the fruits of accessions of feijoa [Acca sellowiana (O. Berg.) Burret] active germplasm bank (BAG), located in São Joaquim, Brazil. The identification of accessions with desirable fruit traits will facilitate species breeding and cultivation. During seven harvests (2004–2017), 10 fruits per plant of 229 accessions were evaluated for fruit diameter, length and weight, skin and pulp weight, skin thickness, pH, titratable acidity, and soluble solids content, in addition to the qualitative descriptors insertion of sepals, fruit shape, sheen of skin, vacuum, color of skin and pulp, and texture and roughness of the skin. Descriptive statistics, correlations, and a multivariate analysis were applied to better understand the nature and magnitude of the variables. The mean +1SD was used to identify the best accessions for breeding purposes. Active germplasm bank accessions revealed significant phenotypic diversity for the physicochemical characteristics of the fruits, and the year effect represented the largest contribution to the variance for all evaluated characteristics, except fruit length. The characteristics total fruit weight, fruit diameter, and skin thickness are strongly related to pulp yield (%). There is high phenotypic diversity in accessions of feijoa conserved in the São Joaquim BAG, which will allow different traits of this species to be genetically improved. [ABSTRACT FROM AUTHOR]