Presented are the results of comparative studies of sod-podzolic soil, typical chernozem and chernozem merged in different land use conditions. While identifying the physicomechanical properties under loading-unloading cycle, it was revealed that the soils with the highest percentage of physical clay demonstrate a higher capability of restoring the soil structure.

This study presents the thermal diffusivity vs. moisture content curves for sandy soils of the East European Plain. Nine undisturbed soil cores 70 mm in height and 50 mm in diameter were studied in laboratory using the unsteady-state method. Thermal diffusivity of air-dry samples varied from 2.30x10(-7) to 4.16x10(-7) m(2) s(-1). The experimental moisture content thermal diffusivity dependencies demonstrated pronounced peaks at 0.03-0.10 m(3) m(-3) moisture contents. Peak values of thermal diffusivity were from 8.25x10(-7) to 9.86x10(-7) m(2) s(-1). Statistical analysis was performed for 23 sandy samples including the newly studied ones and those earlier investigated with the same unsteady-state method. The ranges of sand, silt, and clay within the whole dataset were 73-97, 0-25, and 1-6%; wet bulk density varied from 1270 to 1820 kg m(-3), organic carbon ranged from 0.1 to 1.7%. Each experimental curve was parameterized with a 4-parameter function. The parameters of average moisture content thermal diffusivity dependencies were also obtained for (1) all sandy soils, (2) sandy soils with organic carbon content of 0.5% and greater, (3) sandy soils with organic carbon content less than 0.5%.

It was revealed that the influence of soluble salts on the hydrophysical properties of clayed minerals depends on the nature of minerals, the properties and state of salt (in solution or sorbing), and the region of fundamental hydrophysical characteristics (FHCH). The treatment of clayed minerals by NaCl, MgCl2, Ca(CH3COO)2, and ZnCl2 solutions increased their water-retention in the range NaCl > MgCl2 > Ca(CH3COO)2 ≈ ZnCl2. Pb(CH3COO)2 decreased the water-retaining ability of clayed minerals in all the FHCH range. A differential characteristic of the action MgCl2, Ca(CH3COO)2, and ZnCl2 on smectite is decrease of capillary water deduction.

The number and taxonomic structure of the heterotrophic block of aerobic and facultative anaerobic bacteria were studied in monoliths from a high-moor peat (stored at room temperature and in a refrigerator) and in the peat horizons mixed in laboratory vessels. The monitoring lasted for a year. In the T0 horizon, spirilla predominated at room and low temperatures; in the T1 and T2 horizons, bacilli were the dominants. The continuous mixing of the peat layers increased the oxygen concentration and the peat decomposition; hence, the shares of actinomycetes and bacilli (bacteria of the hydrolytic complex) increased. In the peat studied, the bacilli were in the active state; i.e., vegetative cells predominated, whose amount ranged from 65 to 90%. The representatives of the main species of bacilli (the facultative anaerobic forms prevailed) hydrolyzed starch, pectin, and carboxymethylcellulose. Thus, precisely sporiferous bacteria can actively participate in the decomposition of plant polysaccharides in high-moor peat soils that are characterized by low temperatures and an oxygen deficit. The development of actinomycetes is inhibited by low temperatures; they can develop only under elevated temperature and better aeration.

The analysis of rheological curves of typical chernozem at humidity of maximal swelling allowed revealing that manure application caused dilatant properties at the expense of soil aggregates water-stability increase. Specific capacity increase of maximum destruction of structure in variant with manure improves technological properties of soil at the expense of viscosity decrease and durability limits increase. Under influence of mineral fertilizers sharp decrease of specific capacity of maximum destruction of structure in comparison with control is happened which causes unfavorable structural-mechanical properties.

Установлено, что актиномицетный комплекс окультуренной низинной торфяной почвы отличается высокой численностью и значительным родовым разнообразием актиномицетов; обнаружено присутствие представителей 11 родов: Streptomyces, Micromonospora, Actinomadura, Saccharopolyspora, Microbispora, Microtetraspora, Streptosporangium, Nocardioides, Saccharomonospora, Kibdelosporangium и Thermomonospora. Одни роды выявляются в почве при всех исследованных уровнях влажности, для обнаружения других, так называемых редких (редко встречающихся) родов (Saccharomonospora, Kibdelosporangium и Thermomonospora) достаточен низкий уровень влаги в почве, обеспечивающий им отсутствие конкуренции со стороны более распространенных в почве актиномицетов. Прорастание спор всех исследованных актиномицетов возможно при низкой влажности (aw 0.67). Оптимальным для развития всех актиномицетов является уровень влаги aw 0.98. Полный цикл развития всех актиномицетов, вплоть до спорообразования, происходит только при высокой влажности (aw 0.98).

It was found that the actinomycetal complex of a cultivated low-moor peat soil is characterized by a high population density and diversity of actinomycetes; representatives of eleven genera were isolated from this soil: Streptomyces, Micromonospora, Actinomadura, Saccharopolyspora, Microbispora, Microtetraspora, Streptosporangium, Nocardioides, Saccharomonospora, Kibdelosporangium, and Thermomonospora. Some genera were isolated from the soil under all the studied levels of soil moisture. The so-called rare (rarely occurring) genera (Saccharomonospora, Kibdelosporangium, and Thermomonospora) were isolated upon the low level of soil moisture, which ensured an absence of competition from the more abundant actinomycetes. Spores of all the studied actinomycetes could germinate under the low moisture level (a(w) = 0.67). The level of moisture a(w) = 0.98 was found to be optimal for the development of the actinomycetes. The complete cycle of the development of all the actinomycetes up to spore formation occurring was only observed under the high moisture level (a(w) = 0.98).

Alluvial meadow and swamp floodplain soils were found to be the main habitat of actinomycetes from the Micromonospora genus. Micromonospores were found in these soils in amounts comparable with those of streptomycetes or exceeding them; the population density of micromonospores varied from several hundred to hundreds of thousands of colony-forming units per one gram of soil. The number of micromonospores exceeded the number of streptomycetes in the spring in the organic soil horizons and on plant roots; micromonospores represented the dominant component of the actinomycetal complex in these soils. Moistening conditions equal to the field capacity in the alluvial meadow soil and the maximum molecular capacity in the swamp soil were the most favorable for the development of micromonospores at the intermediate and late stages of the succession.

The effects of different factors on populations of the main groups of soil microorganisms were studied. It was shown that time is the most significant factor. Under experimental conditions, the spatial heterogeneity of the soil with respect to the numbers of the main groups of soil microorganisms was small. A significant correlation was observed between the numbers of the main groups of soil microorganisms in the course of the succession: the highest correlation was observed between the numbers of algae and actinomycetes, as well as between the numbers of actinomycetes and bacteria. A tendency for periodical fluctuations of the populations of some groups of microorganisms with a period of seven days was recorded.