Articles

The purpose of the research was to study interannual and seasonal dynamics of mobile potassium compounds in orchard soil and potassium status of apple trees affected by foliar and ground fertilization with potassium and nitrogen. The investigation was carried out in 2016-2020 growing seasons in soil-climatic conditions of forest-steppe zone of the Central Russian Upland (Orel region). The experiment studying mineral fertilizers’ efficiency has been running since 2015 in the apple orchard with cv.’Ven’yaminovskoe’. The soil of the experimental orchard is loamy Haplic Luvisol. Ammonium nitrate and potassium chloride were used as soil fertilizers with doses N30K40, N60K80 and N90K120. Urea (1%) and potassium sulfate (0,3%) solutions were used for foliar fertilizing. The content of mobile potassium compounds was determined in soil samples taken from a depth of 0–20, 20–40 and 40–60 cm monthly from May to September. The level of mobile potassium in root zone of unfertilized plots was relatively constant during five years. At the same time the regular ground fertilization led to gradual accumulation of potassium in the topsoil. The accumulation rate depended on the doses of fertilizers. When the soil potassium content reached a range 150 mgkg-1 the seasonal fluctuations of index have intensified and vertical migration of potassium occurred. The main factors affecting potassium regime of apple trees were: weather conditions, yield and fertilization rates. Conjugate soil and plant diagnostics showed that the negative effect of a decrease in the availability of soil potassium persists in the subsequent growing season, while can be weakened by applying soil and foliar fertilizers. The highest yield of apple trees in first four years of fruiting observed with soil fertilization by N60K80 in combination with foliar sprays.

Soil N deficiency is one of the main constraints limiting high tea yields worldwide, particularly in Russia. Besides, high dosages of N fertilizers are widely applied for tea plantations, resulting in agrogenic transformation of soils, environment pollution, and a decrease in the tea quality. One of the ways to reduce dosages of N fertilizers is the development of new cultivars with high N use efficiency. In this regard, the effect of genotype on biosynthesis and accumulation of valuable secondary metabolites in tea leaves was studied under optimal N supply and its deficiency in potted experiment. The study was conducted on the most promising local tea cultivars (Kolkhida and Karatum), grown on brown forest acidic soils in the humid subtropics of Russia. Using high-performance liquid chromatography, the contents of catechins, flavanols, alkaloids and theanine were evaluated in tea leaves. Our results showed that N availability stimulated the biosynthesis of theanine more than one order of magnitude and alkaloids (caffeine 3–5 times and theobromine 2–3 times) in both tea genotypes; however, it decreased the accumulation of several catechins and flavanols on average 1,5–2 times. Under optimal N supply, cv. Kolkhida displayed higher accumulation of theanine (by 30–60%) and gallated catechins (by 50%) in the leaves, however cv. higher accumulation of alkaloids (caffeine and theobromine) was observed in cv. Karatum (by 10–20%). N deficiency resulted in greater accumulation of simple and gallated catechins, as well as rutin in cv. Kolkhida, as compared to cv. Karatum. However, the content of the studied metabolites in cv. Karatum was more stable under different nitrogen levels, indicating its lower susceptibility to N deficiency.

One hundred and fifty strains of streptomycetes were isolated from grey and dark grey forest soils, as well as from typical chernozem. The isolated strains were analyzed in Vitro for antimicrobial activity on nutrient media and in grey forest soil against twenty-three collection pathogenic test cultures of fungi and bacteria. Four biologically active isolates with a wide spectrum of action were identified and deposited in the All-Russian Collection of industrial microorganisms of the National Research Centre Kurchatov Institute. They were identified and deposited under the following numbers: Streptomyces xiamenensis TB ВКПМ Ас-2204, Streptomyces anulatus TG ВКПМ Ас-2203, Streptomyces sindenensis TK ВКПМ Ас-2205, Streptomyces flavovirens TT ВКПМ АС-2202. A study of the effect of pre-sowing treatment of wheat seeds by the 15-day cultural liquids of the strains S. xiamenensis TB ВКПМ Ac-2204, S. anulatus TG ВКПМ Ac-2203, S. sindenensis TK ВКПМ Ac-2205 on germination rates and infection with F. graminearum revealed that they inhibited the growth of a pathogenic fungus. Besides, they improved seed vigour and germination of wheat. The resulting strains of soil actinomycetes can be used in biotechnology with an aim to create the new bioinoculants when dealing with phytopathogenic bacteria and fungi. The strains can also be used for stimulating the plant growth, as well as for soil bioremediation in organic farming. Through the application of the HPLC method, specialized antimicrobial metabolites of monosporic strain suspensions were identified. The identified antibiotics are N-Butylbenzenesulfonamide, 1-(1H-Benzo[d]imidazol-2-yl)ethan-1-ol, 2-[(3S)-1-(Cyclohexylmethyl)-3-pyrrolidinyl]-1H-benzimidazole-5-carbonitrile, Cyclo(leucylprolyl), Cyclo(phenylalanyl-prolyl). The identified antiseptics are Cetrimonium and Carvone. The identified phytohormone is auxin indole-3-acetic acid (IAA). Observation of the dynamics of development of introduced actinobacteria under study in soil samples showed high activity of streptomycetes that use chitin. Analysis of the diversity of the prokaryotic complex of the studied soil samples with the application of the high-throughput sequencing of the conserved region of the 16S rRNA gene method revealed during the introduction of S. xiamenensis TB ВКПМ Ac-2204 that its controlling role in the microbial community is due to its antibiotic-forming activity.

The paper demonstrates the importance of creating optimal conditions for mineral nutrition of cereal grasses and microorganisms in oligotrophic oil polluted peat soil under remediation. To establish the effectiveness of using various forms of nitrogen fertilizers in oil pollution, changes in the agrochemical properties and enzymatic activity of the soil, the productivity of cereal grasses and the amount of DNA prokaryotes were investigated. A significant increase in the productivity of plants and the number of bacteria and archaea in oligotrophic peat soil is shown when optimizing nitrogen nutrition, especially pronounced when introducing the ammonium-nitrate form of fertilizer. There is a close relationship between catalase activity in soil and residual oil content in soil.

The study investigated the role of optimized nutrition and the development of a mixture of cereal grasses in oil-contaminated typical chernozem soil with a high level of pollution. The influence of different forms of nitrogen fertilizers at a moderate level of plant nitrogen supply in the presence of oil pollution was investigated using indicators that characterize the agrochemical and enzymatic properties of the soil, as well as the productivity and qualitative composition of remedial plants. Soil contamination with oil at doses of 5 g oil per g of soil and 7 g oil per g of soil had a significant negative effect on the productivity of remedial plants, manifested in a reduction in biomass and the content of major elements (NPK). It was noted that optimized nutrition with mineral fertilizers increases biomass and improves the qualitative composition of plants growing under oil pollution conditions. It was shown that the most favorable conditions for the growth and development of plants were formed when nitrate forms of nitrogen fertilizers were applied compared to ammonium and ammonium-nitrate forms in equivalent doses. A high dependence of the activity of the studied enzymes (catalase, urease, and phosphatase) on the oil content in the soil was noted. When mineral fertilizers used, the enzymatic activity of typical chernozem increases proportionally to the decrease in oil content in the soil, that indicating an intensification of oil hydrocarbon degradation processes when mineral fertilizers are applied.

Structural peculiarities of the organic component of dissolved organic matter (DOM) of typical chernozems (Protocalcic Chernozem), differing in the principal direction of soil organic matter transformation (accumulation or mineralization), has been analyzed in relation to the mineral composition of DOM. To characterize the structural features of the organic component, spectrometry in the ultraviolet and visible range and fluorescence spectroscopy were applied as approaches most often used for these purposes due to the expressiveness and accessibility of the instrumental design. The content of mineral elements (Al, B, Ba, Ca, Fe, K, Li, Mg, Mn, Na, P, S, Si, Zn) was carried out by optical emission spectrometry with inductively coupled plasma. DOM of arable chernozems, where the mineralization of organic matter is the prevalent process of organic matter transformation, was found to possess higher values of the indexes E2/E3, BIX and SUVA254. The latter indicates a smaller MM, a greater contribution of organic matter of microbial origin and aromatic structures to the composition of DOM as compared to soils not involved in agricultural use. The analysis of the mineral component showed Si and Ca were the most abundant elements in the DOM. The involvement of chernozems in agricultural use resulted in a decrease in Ca content and an increase in Si, Fe and Al, what reflected an increase in the degree of weathering of the mineral matrix of chernozems. The conducted rank correlation analysis showed the presence of significant relationships between the structural characteristics of the DOM (E2/E3, SUVA254, MM, BIX, T) and the content of mineral elements (Ca, Al, Fe, Si) indicating the influence of weathering processes on the formation of the soil DOM.

Using the example of data from the article by E.A. Dmitriev et al., the estimation of the required number of soil samples to assess the SOC content in the forest biogeocenosis during monitoring studies is considered. Primary data on SOC content were obtained in the spruce forest at 166 points in layers 0–10, 10–20, and 20–30 cm after removal of the litter. The sampling was carried out at the nodes of a regular grid of equilateral triangles with 1 m side within a regular hexagon with a side of 7 m. The SOC content was determined by the Tyurin method. The original article presents statistics for three zones — near-stem, under-crown and inter-crown space. Spatial variation in all zones and at all depths is high, the coefficients of variation are about 50%. It is shown that the number of replicates required for estimating the average SOC content at a 95% confidence level in the 0–10 cm layer is hundreds of samples and decreases to tens of samples in the 20–30 cm layer. Since the number of repetitions for testing hypotheses about the equality of means depends not only on the confidence level, but also on the power of the criterion used, the required number of repetitions increases several times. Sampling with samples taken from the entire vertical layer of 0–30 cm and forming mixed samples from them reduces the number of required repetitions, however, careful observance of sample preparation, including primary mixing of samples, is required.

We created a three-dimensional (3D) model of the spatial arrangement of soil horizons with broken boundaries using digital images. This technique was tested on a Retisol — an Alfisol with a glossic horizon. Photographs were taken for 11 vertical sections (2.5 cm distance between sections) of the soil profile for an area of 30 × 45 cm. Colorimetric accuracy of the images was tested against measurements of moist soil samples made with a portable spectrophotometer. The selected best images were calibrated using an internal color calibration method for color correction. The images were combined into a common array to build a 3D optical soil horizon map using the CIELAB color space. A protocol for processing the 3D soil images was created that showed 3D soil structure. It was found that the CIELAB color coordinates can be used to distinguish and delineate AE, E, and EB horizons. We then tested the method to assess soil carbon stocks and found that the stocks using the 3D model were 28% higher than when calculated using the 2D model. We conclude that the optical 3D mapping method can accurately represent the 3D structure and can be used to quantify soil horizon variations.