Foliar fertilization makes it possible to quickly provide plants with essential nutrients, mainly micronutrients, which can significantly improve the quality of yields. The aim of this study was to evaluate the effect of foliar fertilization with fertilizers containing calcium and microelements on yielding and fruit quality of highbush blueberry (Vaccinium corymbosum L.). A two-year study was carried out in western Poland in an experimental highbush blueberry production plantation. During the growing season the bushes were treated several times with the following foliar fertilizers: Armurox, BioCal, and Stymjod. The experiment assessed bush growth vigor, yield, fruit quality characteristics, sugar, organic acid, and health-promoting substance content. It was found that as a result of fertilizing highbush blueberry bushes with foliar fertilizers, the leaf blade area and plant yield increased significantly. The fruits collected from those bushes were characterized by a higher mass, firmness, and TSS content. This also applies to blueberry fruit after storage. Foliar fertilization had no significant effect on the content of chlorophyll a and b in the leaves of northern highbush blueberry, on fruit coloration, the content of sugars, ascorbic and citric acids, and the phenolic compounds in them.

Both mycorrhizal and Trichoderma spp. fungi are known for antagonistic effects against certain biological pathogens causing apple replant disease (ARD). The aim of this study was to assess the effectiveness of the bioinoculants based on endomycorrhizal and Trichoderma spp. fungi on the biological properties of soil as well as the parameters of the apple tree growths in a fruit tree nursery under replantation conditions. A two-year experiment was conducted on Jonagold apple trees grafted on to M.9 rootstock in western Poland. The trees were planted in the replant soil—from areas used for the production of apple trees, and in the crop rotation soil, that had not been used for nursery purposes before. A mycorrhizal inoculum and preparations containing Trichoderma spp. fungi were applied to the replant soil. Biological properties of the soil and the growth of the aerial and underground parts of the apple trees were assessed. The enzymatic (dehydrogenases and protease) and respiratory activity of the replant soil was significantly lower than that of the crop rotation soil. The apple trees grew worse when exposed to the ARD conditions. The effectiveness of applied bioinoculants in mitigating the effects of replantation in the nursery were shown. Both the treatment mycorrhization and the application of bioinoculants containing Trichoderma spp. increased the respiratory and enzymatic activity of the replant soil. The growth of the root system and the aerial parts of the trees (including leaves) was much better after the combined use of both types of fungi than in the replant soil that had not received the fungal treatment.

Humic acids are plant biostimulants, which can be used in horticulture as an effective and relatively inexpensive alternative to chemical means of production. The aim of the study was to assess how the fertiliser containing humic acids affected the growth, yield, and quality of strawberry fruits. In 2021, an experiment was conducted on two-year-old strawberry bushes (Fragaria× ananassa (Duchesne ex Weston) Duchesne ex Rozier) of the ‘Rumba’ cultivar growing on a horticultural farm in northern Wielkopolska, Poland. During the growing season, the soil was fertilized by the mineral fertilization and the bushes were sprayed two, three, or four times with the Humi Brown Gold fertiliser containing humic acids. In the experiment, the soil enzymatic activity, biometric parameters of strawberry leaves, fruit yield and fruit quality was assessed. It was determined that, in the experimental treatments where foliar fertilisation had been applied, the activities of proteases and dehydrogenases as well as soil respiration increased by more than double and were significantly higher than in the variants where soil fertilisers had been applied. The strawberry bushes treated with the humic acids fertiliser developed more than 60% larger surface leaves, bloomed more intensively and gave a higher yield. Fruits with significantly higher firmness were harvested from such bushes, with higher weight and extract content than those where the soil fertiliser had been applied. The difference was several tens of percent. This leads to the conclusion that the foliar application of humic acids could be an effective alternative to mineral fertilisation in strawberry plantations.

The influence of climatic conditions on the growth and yield of apple trees can be modified by various factors such as the plant species, its condition as well as stress factors (for example, Apple Replant Disease). The aim of the study was to analyse the influence of air temperature and rainfall on the yield and fruit quality of replanted apple trees of the `Najdared` cultivar. Between 2015 and 2017 an experiment was conducted on apple trees growing on replanted soil and on crop rotation soil in western Poland. The relationship between the trees growing on the replanted soil and crop rotation soil in the years with changeable climatic conditions was analysed with canonical variate analysis based on transformation by linear combination and singular value decomposition. Our study confirmed the fact that air temperature and rainfall significantly affected the yield and quality of apples. The yield of the apple trees growing on the replanted soil was several times lower than the yield of the trees growing on the soil after crop rotation. A similar dependence was observed for the fruit quality characteristics. The previous use of the soil on which the apple trees grew caused differences in their reactions to the meteorological conditions. The occurrence of ARD caused a greater decrease in the yield of trees due to low temperature.