Vol 16, No 1 (2021)

The experiments revealed that the studied fragments of Rosa acicularis L. coenopopulation were normal and full-fledged with single-vertex ontogenetic spectra. They are able to form self-sustaining habitats for several generations and spread over a significant territory. Three periods and six ontogenetic states were distinguished in the ontogenesis of Rosa acicularis L. The age structure had three types of spectrum - left-sided, centered, and right-sided. The difference in the ontogenetic structure depends on influence of anthropogenic factor, ecological and coenotic conditions of rose habitats, and variations in climatic conditions. When analyzing the parameters of coenopopulations, we found that the best conditions for existence of Rosa acicularis L. were in the berry pine forest (FCP5) in the park named after Foresters of Russia and reed grass pine forest (FCP1) in Uktus forest park, where the habitats were characterized by high morphological indicators, numbers and high values of the pregenerative fraction.

In agricultural production, it is important not only to achieve a high productivity, but also to ensure its stability. To obtain high and stable yields, it is necessary to have information on the adaptability of crops varieties and hybrids to a specific cultivation zone. The article analyzes the results of the field experiment on the variety testing of sweet pepper. To assess the variety for adaptability to natural conditions and cultivation technology in the Astrakhan region, such parameters as plasticity and stability of the variety were used. To characterize the ecological plasticity, the regression coefficient b_i was determined, which characterizes response of the cultivar to changes in cultivation conditions. To characterize the parameter of stability, the standard deviation from the regression line σ²d. was calculated. All calculations were carried out according to S.A. Eberhart, W.A. Russell as presented by V.Z. Pakudin.

Field experiments were carried out on chestnut soils of Piedmont Dagestan in 2018-2020. Hybrids of grain corn treated with different growth stimulants were the object of еру research. The experiments showed that the harvesting ripeness of hybrids ROSS 299 MV and Mashuk 355 MV occurred 2...5 days earlier after treatment with growth stimulants compared to the control. The growth stimulants used in the experiment did not have a significant effect on seed germination rate. Among the studied hybrids, the highest seed germination were observed in Mashuk 355 MV hybrid. The highest values of leaf area and net productivity of crops were in hybrid Mashuk 355 MB. Plants treated with growth regulators had higher leaf surface by 4.4% and 5.5%; 6.0 % and 8.4%, respectively. Approximately the same dynamics was recorded for photosynthesis net productivity and accumulation of dry matter. Mashuk 355 MV hybrid showed the best yield, which was 30.5; 31.5 and 32.5% higher respectively, compared to the standard. Productivity of corn hybrids treated with growth regulators increased significantly. The highest data were observed on plants treated with Megamiks N₁₀ growth regulator, which were higher than the control data by 30.0 and 32.5%, respectively. Aminokat 30% growth regulator increased corn productivity by 23.7 and 24.7%, respectively. Sufficiently high indicators of yield structure were 10 recorded in Mashuk 355 MV hybrid in the variant with the Megamiks N₁₀ growth stimulator.

Synchytrium endobioticum (Schilb.) Percival. is a pathogen of potato wart disease and has a restricted distribution on the territory of the Russian Federation. Its main pathways are infected potato tubers and different planting material containing soil particles infected with spores of the fungus. One of the main problems is the use of toxic chemicals during detecting the disease in laboratory methods of direct soil testing to identify resting spores. This paper presents the assessment of molecular methods of soil diagnosis for detection of S. endobioticum by direct extraction of fungal DNA from soil samples using the MetaGen reagent kit. Identification was performed using the ‘Fitoskrin. Synchytrium endobioticum-RT’ kit. The kit was pre-tested using DNA isolated from potato warts by various commercial kits. It was found that the optimal method of DNA isolation from the warts was using the ‘FitoSorb-Avtomat 48’ kit at the Tecan robotic station. Studies have shown that the sensitivity of the direct DNA extraction method from soil samples with various infection levels is the same as that of flotation method using carbon tetrachloride. Moreover, this method makes it possible to work with soil samples of different types, including peaty soils.

The article provides a predictive assessment of longevity of Ulmus pumila L. stands in the Astrakhan Zavolzhye. The effi and expediency of renewable logging for rejuvenation and increasing the longevity of plantings in the semi-desert were confi The classifi of ecotopes of the Astrakhan Zavolzhye on suitability for cultivation of protective and shadow elm plantings on pasture lands was developed and presented. In the Caspian region, Ulmus pumila became widespread in forest reclamation of semi-desert lands in the 1950s. Since then, till the beginning of the 1990s, Bogdinskaya research agroforestry experimental station laid on the sandy massifs about 1 thousand hectares of Ulmus pumila L. plantings, which currently amounts to 18…24 %. The long-term practice of using protective shade Ulmus pumila umbrellas has shown their signifi ecological effect on functioning pastures. The aim of the research was to develop an improved technology for creating long-lived protective shade stands of Ulmus pumila on degraded pastures of the Astrakhan Zavolzhye. The research was carried out using generally accepted methods of stand forest taxation by A.P. Anuchin (1961), 1. Bitvinskas (1974) and A.S. Manaenkov (2001). Soil conditions were studied by drilling sounding to 3 m depth. The results of the research revealed that the longevity of wood species in the dry-steppe zone was determined mainly by two factors: productive moisture in the soil and salinity level. The most favorable growing conditions for Ulmus pumila were unsalted (to a depth of at least 3 m) brown sandy soils, sandy loam soils, dark-colored swale soils with periodic redistributed accumulation of moisture. In arid conditions of the Astrakhan Zavolzhye in island plantations (group of trees, “umbrellas”, 0.5…1 ha parts of forest area) and optimal growing conditions without logging and reforestation, Ulmus pumila lives up to 60…70 years.

The article presents the results of field experiments on deepening the arable horizon of gray forest medium loamy soil to increase its fertility through applying organic fertilizer under PY-3-35 layer plow to a depth of 25…27 cm. Low mineralization of organic fertilizer during layer cultivation under oxygen deficiency conditions contributed to accumulation of humus in soil by 6.6 t/ha more than during conventional plowing, and by 7.5 t/ha - than during disking. It also improved water-physical and biological properties of soil: number of water-resistant aggregates increased by 4.6 and 5.3 %, soil density lowered by 0.03 and 0.04 g/cm³, number of earthworms increased by 3...6 individuals, expanded reproduction of fertility was provided, productivity of arable land increased by 7.0 and 6.7 % and crop quality increased compared to conventional plowing and disking, respectively. Deep manure incorporation extended life of organic fertilizer up to 5 years, while after conventional plowing and disking this process lasted only 2...3 years. It is not economically and environmentally beneficial, since frequent application requires a lot of fuel, and a large amount of harmful chemical compounds contained in combustion products is dumped into the environment.