Efficient plant-growth-promoting rhizobacteria (PGPR) used as biofertilizers and biological control agents are promising substitutes for minimizing the application of synthetic agrochemicals in crop production. We studied the effect of PGPR strain Bacillus velezensis BS89 alone and in combination with three forms of nitrogen fertilizers (ammonium nitrate, carbamide, and ammonium sulfate) on the productivity of two strawberry varieties in three-year field experiments. We first showed that the application of PGPR Bacillus velezensis BS89 on strawberries demonstrated the same effect as the application of nitrogen fertilizers. Use of the strain BS89 increased the chlorophyll content in plant leaves by 2.7–6.8%, and also increased the yield of berries by 6.7–36.4% for cv. Rusich and 7.5–19.3% for cv. Troitskaya depending on the form of nitrogen fertilizer. The best results in the yield of strawberry plants of the cv. Rusich were achieved in the variant BS89 + ammonium nitrate (41.9–57.4%), and the cv. Troitskaya—in the BS89 + carbamide variant (8.1–38.8%). Three-year use of strain BS89 for cv. Rusich resulted in an increase of runner’s weight by 212.1%, and also the weight of the roots by 120%, thereby significantly improving the mineral nutrition of plants. This is mainly associated with the plant growth-promoting activity of Bacillus velezensis BS89, which was able to produce a high amount of IAA—494.1 µg/mL. We believe that the PGPR strain BS89 can be successfully used for growing strawberries. However, each variety requires careful selection of the composition of nitrogen fertilizers and analysis of the compatibility of fertilizers and the PGPR strain.

Biomodified mineral fertilizers (BMFs) were produced by enriching the ammophos fertilizer with PGPR Bacillus velezensis BS89 with the use of two technologies: BMF 1, the ammophos fertilizer with the addition of spores of Bacillus velezensis BS89 on a dry carrier (diatomite); and BMF2, ammophos granules treated with spores of Bacillus velezensis BS89 in a cell suspension. The effects of BMFs on maize growth and productivity and the rhizosphere bacterial community were assessed. BMFs significantly increased maize growth, dry matter, minerals, starch and protein contents in maize grain. The application of biomodified mineral fertilizers resulted in the significant increase in the yield and some parameters of maize plants such as ear length and number of kernels in the row. The yield was increased by 7.5–7.6%, ear length by 9%, and number of kernels in the row by 6.7–7%, as compared with ammophos. However, we found no considerable differences in the composition of the bacterial community of the maize rhizosphere after the use of BMFs as compared with the use of ammophos at the level of the phyla, which was confirmed by the ecological indices of biodiversity: the Shannon index and the Simpson index. Comparison of the experimental variants with bulk soil showed differences in the microbiome composition of the dominant bacterial phyla. A greater abundance of Proteobacteria and Bacteroidetes and a lower abundance of Chloroflexi was registered in bulk soil as compared with the other experimental variants where maize plants were present. The highest percentage (5.3%) of unidentified taxonomic phyla was also found in bulk soil. Our studies showed that maize is the main structuring factor during formation of the microbiome composition in the rhizosphere. The application of biomodified fertilizers BMF1 and BMF2 considerably increased the abundance of bacteria representing the minority of the community, namely, those from the phyla Verrucomicrobia, Chloroflexi, Planctomycetes, Proteobacteria, Firmicutes and Chlamydiae, as compared with the use of ammophos. Thus, the application of biomodified mineral fertilizers is a promising agronomic and ecological strategy for boosting maize yield and the quality of grain under field conditions.

The paper analyzes the adaptive abilities of black currant cultivars of plants for the assimilation of nickel from highly cultivated sod-podzolic soils containing 10.7-14.1 mg / kg of fluent nickel. Plantings were monitored at experimental plantings of ARHIBAN (Moscow region) on 9 black currant cultivars: Oryol Serenade, Belarusskaja sladkaja, Zagadka, Vologda, Triton, Biryulevskaya, Titania, Orlowsky waltz, Exotica. The agrochemical properties of the soil, the content of fluent nickel in the soil, and its content in the fruits of black currant plants were determined. Based on the analysis, the coefficients of nickel assimilation by black currant plants were calculated and statistical dependencies of its accumulation indicators on agrochemical properties of sod-podzolic soils at different depths of the root layer were determined. According to the results of research, regression dependences of the accumulation of nickel in black currant fruits on the indicators of the agrochemical properties of the soil and the content in the soil of fluent nickel were constructed. It was established that the nickel content in black currant fruits primarily depended on the acidity of the soil, on the content in the soil of fluent nickel, alkaline hydrolysable nitrogen and fluent potassium. Black currant cultivars Belarusskaja sladkaja, Vologda, Triton, Biryulevskaya, Titania were more resistant to soil pollution with nickel.

Current approaches to land use and agricultural production are increasingly aimed at achieving high productivity through the use of crop rotation, siderites, integrated plant protection, minimized soil cultivation, microbiological fertilizers, and biological preparations. Modern microbiological preparations enhance the uptake of nitrogen and ash elements by plants, improving the rhizosphere of plants and the quality of strawberry fruit. Aim. To establish the effect of Extrasol applied using drip irrigation and various forms of mineral nitrogen fertilizers on the chemical composition of leaves and fruit of garden strawberry.Materials and methods. Garden strawberry plants of the Rusich and Troitskaya cultivars were treated with Extrasol and mineral fertilizers. Experiments were carried out in 2017–2020 at open-ground plots of the Federal Horticultural Center for Breeding, Agrotechnology and Nursery (Moscow Oblast). The experimental plots were characterized by soddy podzolic soils of medium-loam granulometric composition. Plant samples were analyzed using conventional methods. The experimental scheme consisted in the application of various nitrogen fertilizers (ammonium nitrate, urea, and ammonium sulfate) either in combination (2 mL/L of the working solution) or without Extrasol. Conclusions. In strawberry cv. Rusich, the use of ammonium nitrate increased the calcium content in plant leaves and decreased its content in fruit, which negatively affected the crop quality. Mineral fertilizers applied in combination with Extrasol increased the nitrogen content in leaves and fruit. The combined use of the amide form of nitrogen (urea) and Extrasol adversely affected the level of nitrates in cv. Troitskaya fruit. The use of fertigation and Extrasol reduced the amount of soluble dry substances in strawberry fruit.

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