No 12 (2025)

In laboratory experiments, the study was conducted of the size of nitrogen losses due to leaching, as well as the dynamics of ammonium and nitrate nitrogen content in the soil when applying conventional and biomodified urea (BMU), urea-formaldehyde (UF) fertilizer and ammonium nitrate. It was shown that nitrogen was washed out only in the nitrate form from the ammonium nitrate, with losses amounting to 38.7% of the amount applied. The accumulation of nitrate in the soil due to biological oxidation of different forms of urea occurred most intensively on the 7^th–21^st days of the experiment. When UF is applied, the release of ammonium nitrogen occurs extremely slowly, while all the ammonium formed undergoes immediate oxidation to nitrate, as a result of which the content of mineral nitrogen in the soil, when UF is applied, during the 1–7^th week of observation was always 1.6–3.0 times lower compared to other fertilizers.

In a small-scale field experiment, the effect of pre-sowing seed treatment with 2 variants of bentonite clay (native (natural) and its acid-activated forms) on the yield of green mass and corn cobs was studied. Montmorillonite K-10 was used as the standard. Experiments conducted on corn of the Krasnodar 201 AMB variety in 2024 showed a comparable, significant increase in the yield of green mass, including cobs, in all processing options. The results obtained indicate the expediency of using bentonite clays for pre-sowing seed treatment.

Molecular computer modeling of the possibility of blockade by azaheterocyclic structures of potential targets, which are subcellular structures of fungal cell covers, was performed. The possibility of using ergosterol (the main structural element of the fungal cell membrane), lanosterol 14α-demethylase (an enzyme of the cytochrome P450 superfamily responsible for the conversion of lanosterol to 4,14-dimethylergostatrienol), ergosterol-dependent Na⁺/K⁺-ATP-ase (a membrane enzyme), and squalene monooxygenase (an enzyme that catalyzes the conversion of squalene to squalene epoxidase, which is a lanosterol precursor) as cellular targets. A good correlation has been shown between the choice of subcellular structures as cellular targets and the results of computer modeling, which makes it possible to select possible target binding sites with potential ligands. The results of computer modeling are confirmed by data from the preliminary forecast of PASS, according to which the biological activity of the target compounds suggests the presence of fungicidal or antimycotic action with a probability of 72–93%. The structure of the target compounds is confirmed by IR-spectroscopy, ¹H, ¹³C NMR spectroscopy, ¹H-¹H (NOESY), ¹H-¹³C (HMBC) 2D NMR spectroscopy, high-resolution mass spectrometry, and X-ray diffraction analysis. It was found that the target compounds in most cases showed moderate fungicidal activity against the test cultures of Mucor mucedo mold fungi, comparable to the activity of the comparison drugs phytolavin and previcur. The physicochemical characteristics of the target compounds have been studied, which meet the requirements for the possibility of their thermal distillation well. It has been shown that the physico-chemical properties of the target compounds allow their further use as fumigants of fungicidal action.

The retrospective carbon balance (CB) in soils under cereal crops of the Russian Federation for the period 1960–2023 is analyzed. The CB estimate was established by comparing the data of new carbon entering the soil (plant residues and crop byproducts) and heterotrophic soil respiration (R_H). The R_H was determined based on the nitrogen mineralizing capacity of soils over a year-round period of time. It is shown that in agriculture in Russia, for a long time, a negative carbon balance was formed under cereals crops. If from 1960 to 1980 there was a decrease in the C_org deficiency in the soil from –0.4 to –0.16 t/ha/year, from the beginning of the nineties to the present the deficit has been maintained at –0.4…–0.6 t/ha/year. Over a 60-year period, Russian agriculture has shown a close positive relationship between the total biological productivity of cereals (NPP) and heterotrophic soil respiration (R_H). It is shown that if all (and not just NPP) by-products of cereal crops had been used as fertilizers in the previous decades, the loss of soil organic carbon would have been practically reduced to zero.

In recent years, there has been an increased interest in drugs based on bacteria of the genus Streptomyces, which have not only a fungicidal, but also a growth-regulating effect on plants. The nature of the effect of such drugs on the photosynthetic activity of plant leaves, especially of legumes, is still poorly understood. In this regard, in 2021–2024, the reaction of 3 varieties of seed peas (Pisum sativum L.) to the pre-sowing treatment of seeds with 2 laboratory samples of local S. castelarensis A4 and S. antimycoticus 8A1-3 by the level of accumulation of photosynthetic pigments by leaves, comparing them with the action of the chemical mordant Pioneer, CS and the biological preparation Pseudobacterin-2 (the active agent is Pseudomonas aureofaciens) was studied in the field. It was found that the conditions of the growing year explained 41.8–67.1% of the variation in pigment content, the genotypic features of the studied varieties – 10.7–12.5%, seed treatment – from 1.1 to 2.5%. On average, in the experiment (4 years × 3 varieties), the stimulating effect of all the studied preparations on the accumulation of pigments in pea leaves prevailed. For Chl a, the effectiveness of the drugs decreased in the order of Pioneer (8.25%) – S. antimycoticus 8A1-3 (7.48%) – Pseudobacterin-2 (3.68%) – S. castelarensis A4 (2.83%). For Chl b, the order of preparations was slightly different: S. antimycoticus 8A1-3 (15.37%) – Pseudobacterin-2 (13.70%) – Pioneer (11.27%) – S. castelarensis A4 (8.45%). The stimulating effect of drugs on carotenoid content decreased in the order of Pioneer (8.98%) – S. antimycoticus 8A1-3 (8.40%) – S. castelarensis A4 (3.48%) – Pseudobacterin-2(1.57%). The pigment complexes of pea leaves of the E-483 variety reacted best to seed treatment with preparations of local Streptomyces strains (depressive effect was noted only in 8.3% of observations), the reaction was slightly worse in the Falyonsky Yubileyny variety, where depression was noted in 20.8% of observations. Most often, the drugs led to a depression of pigment accumulation in the leaves of the Falyonsky Usatiy variety (38% of the experimental variants), the stimulating effect was manifested only in 19% of observations.

Rhizospheric bacteria help plants overcome the stress of drought and waterlogging of the soil, and they are used in crop production to increase crop yields. However, it has not been sufficiently studied whether a single bacterial strain can be equally effective in drought and waterlogging of the soil. The reaction of wheat (Triticum aestivum L.) to treatment with 6 strains of bacteria during waterlogging was evaluated in laboratory and field experiments (“Baymakskoye” Agricultural Research Institute of the Russian Academy of Sciences) and the data were compared with previously published results of a similar experiment in arid conditions. Excessive watering reduced the height, weight of plants, and the total amount of chlorophylls, and the use of bacteria fully or partially normalized these indicators. The most successful treatment was with Pseudomonas mosselii strain 5(3), which was previously inferior to P. protegens DA1.2 and P. chlororaphis IB-6 strains against the background of drought. In the extremely rainy field season of 2024, plant weight in the tillering phase and wheat yield increased both in plots with strain 5(3) (up to 24.6 and 20.7%) and strain DA1.2 (up to 50.7 and 20.0%) due to an increase in the number of productive stems and grain weight in each ear. Thus, during waterlogging and drought, different types of bacteria provided an advantage, but the dynamism of weather conditions in the field could smooth out the differences observed in controlled laboratory conditions.

There are more than 20 methods for determining available phosphorus in soil in the world. One of the most difficult methodological tasks is to select a solution for soil extracts that would extract only plant-available phosphates from the soil and would not transfer low- and inaccessible phosphorus compounds into the solution. All chemical methods used usually include soil extraction with solutions of different pH, a certain soil : solution ratio, and different interaction times. In Europe alone, there are more than a dozen different methods used as standard methods for determining available phosphorus in soils. In Germany and Austria, the lactate method (CAL) is widely used for routine soil analysis, while in the USA, Canada, and the Czech Republic, the Mehlich method is used for acidic and neutral soils. It uses a multi-element extractant (a mixture of 0.2 M CH₃COOH, 0.25 M NH₄NO₃, 0.015 M NH₄F, 0.013 M HNO₃, 0.001 M EDTA), which allows for the simultaneous extraction of P, K, Ca, Mg, Na, Cu, Zn, Mn and Fe. In European countries, the Olsen method is generally accepted for carbonate soils. It is based on the extraction of available soil phosphates with a 0.5 M NaHCO₃ solution with a pH of 8.5. In Russia, the following standardized methods are used to determine available phosphorus: for sod-podzolic and gray forest soils – the method of Kirsanov (0.2 M HCl, with a soil: solution ratio of 1 : 5), for non-carbonate chernozems – the method of Chirikov (0.5 M CH₃COOH, 1 : 25), for carbonate soils – the method of Machigin (1% (NH₄)₂CO₃, 1 : 20). In some countries, for example in Brazil, anion exchange membranes have begun to be used. In general, the availability of phosphorus for plants is mainly determined by three indicators: 1 – the concentration of P₂O₅ in the soil solution (the “intensity” factor), determined in low-salt extracts (the method of Karpinsky–Zamyatina, Skofield), 2 – the amount of P₂O₅ in the solid phase of the soil, which can be easily accessed by plants (the “capacity” factor), methods of Kirsanov, Chirikov, Machigin, Olsen, Mehlich, and others, 3 – the ability of the soil to maintain the concentration of P₂O₅ in the soil solution at a sufficiently high level for a long time (buffer capacity of phosphorus, PBC). The most promising methods are those based on the use of anion exchange membranes, in which, due to the sorption of phosphorus from the solution by anionites, further desorption and the entry of P₂O₅ from the soil occurs, which allows the most complete imitation of the absorption of phosphorus by the root systems of plants and the most complete convergence of the results of the methods with the efficiency of phosphorus fertilizers and the yield of agricultural crops. This will allow the rational use of phosphorus fertilizers due to the limited reserves of phosphate raw materials.