Contemporary trends in horticulture are aimed at limiting the use of mineral fertilizers to the necessary minimum, which is to guarantee adequate profitability of production while maintaining high-quality fruit and at the same time preventing environmental pollution. Thus, in the presented study, we investigate the effect of diversified nitrogen fertilization on soil mineral nitrogen content during vegetation season, yielding of apple trees and the nutritional status of apple leaves and fruits. We compared several ammonium nitrate treatments as well as growth without fertilization as a control. The results of our study show that under the conditions of humus-rich soils and with appropriate agrotechnics, N mineralization from the organic matter available in the soil may completely cover demand of apple trees for this component. Achieved outcomes clearly revealed that nitrogen fertilization in the amount of 100 kg N · ha−1 on the entire soil surface carries a real risk of groundwater contamination, and the same nitrogen dose applied within the grassland does not bring any production effects, therefore it should be considered as unjustified. Obtained results revealed that in a rationally managed, fully fruiting apple orchard, the annual dose of N should not exceed 50 kg N∙ha−1. This dosage of N should fully secure the nutritional needs of apple trees, guaranteeing their high yield and complete safety for the environment. What is important is, nitrogen fertilization strongly affects macroelemental composition of apple leaves and fruits.

This study investigated the antioxidant status of roots, leaves, and fruit upon microbial inoculation (AMF+PGPR, arbuscular mycorrhizal fungi, and plant growth-promoting rhizobacteria, respectively) of young organically farmed apple trees over two growing seasons. Three cultivars—‘Topaz’, ‘Chopin’, and ‘Odra’—were selected to test the relationship between inoculation and enzymatic and non-enzymatic antioxidant components. The antioxidant metabolism was highly dependent on tissue type and growing season. The greatest effect on antioxidant status following application of the inoculum was found in roots, then leaves, but it was almost negligible in fruit. Roots were influenced most by application of the inoculum in the first growing season, while leaves were influenced most in the second season. Considerable differences between the inoculated and control plants were found for root glutathione reductase (GR) and catalase (CAT) activity, as well as glutathione and ascorbate contents; root phenolics were not influenced by inoculation. In the case of leaves, effect of microbial inoculation on GR activity was revealed in the first growing season, while for global phenolics in the second season, and only the concentration of glutathione was significantly higher in the leaves of inoculated trees in both growing seasons. Leaf ascorbate content and CAT activity were not influenced by the microbial inoculation. The control and inoculated trees expressed a similar total antioxidant capacity, irrespective of the tissue type tested. Furthermore, the response of the cultivars to inoculation varied and also changed in consecutive growing seasons. Based on this study, it is likely that the effect of microbial inoculum as a tool for enhancing health-promoting properties in the fruit of perennial plants is weaker than that described for vegetables where different plant organs are edible.

The desire to reduce the negative impact of crops on the environment, as well as the growing concern for consumer health, is increasing interest in organic fruit production. In this context, the development of new environmentally friendly agrotechnical methods which allows for reducing the use of organic fertilizers by improving the nutrient use efficiency and consequently decreasing the leaching of them is a task of a great importance. The main purpose of this study was to evaluate the effect of mycorrhizal arbuscular fungi (AMF) combined with plant-growth-promoting rhizobacteria (PGPR) on growth and nutritional status of apple trees cultivated on a silty-loam, rich in clay minerals and humus soil under organic farming conditions. Thus, a trial was established in an experimental orchard in Wilanów in Central Poland with three cultivars (‘Topaz’, ‘Odra’, and ‘Chopin’) and a promising clone, U 8869. Trees were or were not inoculated with AMF + PGPR within a split-block experimental design with four replicates. According to the results, mycorrhizal frequency obtained in the inoculated tree roots was on average two-fold higher than in the roots of the control plants. After four years of AMF + PGPR inoculation, 24% higher trunk cross-section area (TCSA) was observed, with the nitrogen and magnesium concentrations in leaves increasing, on average, by 7.8% and 64.2%, and phosphorus and potassium content decreasing by 37.2% and 46.5%, respectively. This study shows that using AMF + PGPR inoculum supports tree roots colonization by AMF. As a result, better nitrogen nutrition status is observed that promote vigorous growth of trees and more efficient uptake of magnesium from the bulk soil. On the other hand, lower phosphorus content in inoculated tree leaves might be explained by a dilution effect, and potassium decrease could occur as a result of fungus–plant competition in conditions of this element deficiency in soil.

The aim of this study was to investigate the effect of alternative soil maintenance systems in a ‘Gold Chief’ apple orchard to the herbicide strip on tree growth, yield, and optimal fruit quality during 2012–2016. We compared several floor management systems: organic mulch comprised of Miscanthus spp., mechanical cultivation, black polypropylene cover, and herbicide strip as the control, with particular emphasis on the suitability and effectiveness of the organic mulch. During this five-year experiment Miscanthus spp. mulched trees grew most vigorously and significantly more than trees from other systems. The increment of the trunk cross-sectional area was higher for Miscanthus spp. mulched trees when compared to both mechanical fallow and herbicide strip. On average, fruits from trees grown in Miscanthus spp. plots were significantly larger than fruits from mechanical fallow and black polypropylene cover plots. The cumulative yield from the entire experiment was not significantly different for organic mulch, herbicide strip, and black polypropylene cover and was significantly higher than the mechanical cultivation. Different floor management systems had a significant effect on the solid soluble content in fruit both directly after harvesting and after storage. Our study shows that organic mulch can be a good alternative for soil management in orchard production systems.

The aim of the study was to describe the physicochemical properties, with particular emphasis on nutritional value, of apples ‘Chopin’ and clone ‘JB’. The new cultivars were compared with the cultivars commonly cultivated in Polish orchards, namely ‘Gala Brookfield’, ‘Šampion’, ‘Ligol’ and ‘Idared’. The study focuses on the evaluation of physicochemical characteristic (firmness, soluble solids content and titratable acidity) and the content of monosaccharides, sucrose and organic acids based on HPLC with an RI detector. In addition, the nutritional value of apples were described separately for the flesh and peel of the fruit, focusing on the assessment of the antioxidant activity and the content of total polyphenols, phenolic acids, flavonols using the HPLC technique. ‘Chopin’ and ‘JB’ clone apples are characterized by very high acidity, over 1%, which is related to the high content of malic acid. The red flesh ‘JB’ clone is characterized by a high content of bioactive compounds in both the peel and flesh of apples. High temperatures and a lack of precipitation contribute to a higher polyphenol content in apples, which proves that apart from the genetic features of the cultivars, the climatic conditions also determine the nutritional value of the fruit.