Diagnostics of such important feature as the structure of soil cannot be based only on field studies of the morphology of the soil profile, but primarily should be supported and logically substantiated by analytical laboratory research. During the research process was chosen the optimal and available sieve method of modifying of N.I. Savinov, which results indicate the ratio of aggregates of different sizes and their water resistance in soil. To establish how the size of structure affects the properties and mode of soil and whether it is resistant to water movement and strong mechanical load. Are highlighted the study results of structural and aggregative state of light gray forest surface gleyed soil in fallow land and variants of 50-year-long agricultural use. It is established that the inclusion of soil in farming without fertilization and in systematic mineral fertilization promotes the formation of mezoaggregates, but also leads to significant powdering of them, which is confirmed by the morphological diagnosis of soil profile and poor water resistance. The structural condition of arable layers both of the control without fertilization and the variant of mineral fertilization by the amount content of agronomically valuable aggregates is better in comparing with the fallow (39, 6), and this is 55.1 on the control and 52.0 in the variant of only making mineral fertilization. The coefficient of structuring is 1.23% and 1.08% accordingly against 0.66% in fallow. These results can be connected, first of all, with feature of size distribution of light gray forest soil, which should be considered in their study.
Aim. To determine the regularities in the formation of water-stable structure and to obtain the objective integral information about the process of break-up and consolidation of the water-stable structure under agrogenic and postagrogenic load on the main soil types of the Central Forest-Steppe of Ukraine. Methods. The field method – the soils of chernozem type were investigated (seven chernozem-like soil types of different granulometric composition and humus content) in the central part of the Forest-Steppe of Ukraine, the laboratory analytical method (wet sieving of soil structure), the mathematical-statistical method (non-parametric statistics, factor, cluster, and fractal analyses). Results. The analysis of the water stability of the structure of chernozem-like soils in the Forest-Steppe demonstrates the perspectives of using modern statistical methods: fractal, factor, cluster methods, and the method of non-parametric statistics, which demonstrates their sensitivity to insignificant changes in the distribution of water-stable aggregates within the agronomically valuable interval. The soil types of postagrogenic maintenance form the distribution of water-stable aggregates, making up “prevailing” sizes of aggregates in the interval of sizes of 5–3 and 2–1 mm, which ensures the persistent state of the re-distribution where the index of Hurst has the values of H > 0.75. The agrogenic impact on soils changes the re-distribution of water-stable aggregates, destroying their natural distribution and ensuring the antipersistent state of the distribution with low stability (D > 1.43 and Н < 0.58). Under postagrogenic maintenance of soil types, there is a stable mutual connection between water-stable aggregates, structural units, and ESP (R = +0.78), and in the total of correlation relations, the direct and inverse correlation relations of R> ± 0.55 level are >30 % with the 1.5 to 1 ratio in favor of inverse proportion relations which ensures a high level of self-regulation for the hierarchical organization of the structural and water stable state. Conclusions. The determining index, characterizing the stability level of the water-stable structure, was found to be the content of water-stable aggregates of 3–1 mm and > 0.25 mm and the weighted average diameter of water-stable aggregates within the agronomically valuable interval of sizes that demonstrated a strong correlation (R = ± 0.76–0.96 ± 0.02) with fractal dimensionality (D > 1.4) and the index of Hurst (Н) which allowed for forming a gradation scale for the evaluation of the water-stable structure and the degree of agrogenesis manifestation of soils in the Forest-Steppe of Ukraine. In terms of the rate of agrogenesis manifestation via the formation of the degree of the water-stable structure, the soils of chernozem type were divided as follows: gray forest low-humus heavy-loamy light-clay soil on carbonate loess-like clay < typical low-humus heavy-loamy light-clay chernozem on loess-like clay < meadow-chernozem low-humus carbonate heavy- loamy soil on loess-like clay < typical medium-humus heavy-clay chernozem on loess.
The results of research in a stationary study, based in 1992 on gray forest coarse-grained loamy soil, on the impact of long-term chemical reclamation and0,0 various supply systems (mineral, organic, organo-mineral) on the nitrogen regime. Nitrogen is extremely important in agriculture, as all processes, photosynthesis, volume of substances and distribution of the level of yield and its quality are impossible without this element. In the total coverage of the country, the share of soils of forest origin exceeds 33 %, and among agricultural lands – 25 %. Given the content of humus and its total reserves, the integrated indicator of soil formation and the most important characteristic that determines the overall habit of the soil, in the articles above, change it from the above factors. It can also be shown that the content of gross nitrogen reflects the humus content, which is determined and differs from the humus content of the residual. There is a high density correlation between these indicators for all different studies (r = 0,991). The obtained data indicate that only with the use of greens and by-products of precursors and measured doses of mineral fertilizers with the use of liming achieved by the size of the total nitrogen to the initial level. The growth of the composition is 0,36 – 0,45 t / ha and in this case we can state the expansion of its reproduction. Only after mineralization nitrogen of organic compounds becomes available to plants. The form of nitrogen, which is easily hydrolyzed, is a fairly reliable indicator of the provision of this element. To classify the test content with the content of mobile compounds 81,2 – 103 mg / kg belong to the user groups with a very high degree of supply, but the degree hydrolyzes organic substances in high quantities (9,6 – 10,2 %). With the combined use of green manures, non-marketable plant products, single doses of mineral fertilizers in a combination of lime achieved growth of 27,5 % on the restoration to control of this form of nitrogen. For the above complex of nutrients at an increased content of 16,5 mg/kg to control the amount of N-NO3- + N-NH4 +, as well as 7,4 mg / kg of nitrifying capacity of the soil. The studied gray forest soils belong to the group of soils with low humus content and its total reserves, which are inherited from the original pedogenesis and modern soil formation processes. Under the influence of a set of agronomic measures for a long time the type of humus does not change, which indicates the invariability of the direction of soil formation
The state of microbial communities in gray forest soil contaminated with heavy metals at a dose of 5, 10, 100 MPC, in the presence and absence of vegetative phytosynesis (corn) has been investigated in model experiments. The protective function of the phytocenosis concerning several groups of microorganisms, in particular, azotobacter and polysaccharide-synthesizing bacteria, has been shown. The number of azotobacter in the rhizosphere of plants exceeds the indices of soil without plants: in the control by 3.33%, at 5 MPC – 36.6, at 10 MPC - by 95.6%. The indicative function of azotobacter has been confirmed concerning soil pollution with heavy metals. The number of azotobacter is decreased with increasing the pollutant dose in the soil without plants: at 5 MPC - by 2.64 times, at 10 MPC - by 6.67 times, the corresponding indicators for plants rhizosphere are 2.05 and 3.52 times. Azotobacter is not detected by the method of overgrowing soil lumps at the maximum level of soil contamination with heavy metals (100 MPC). The mycelial forms of microorganisms (micromycetes) are highly resistant to contamination with heavy metals that have been confirmed. The activity of mineralization of organic substances, including hummus, is decreased with the increasing of pollutant dose in the soil has been shown. The pedotrophy index decreases at 5 MPC by 3.16%, at 10 MPC - 30,9, and 100 MPC - by 46.8% in soil without plants. Similar numbers for variants with plants fluctuate between 14.2 and 105.4%. The conclusion about a lesser susceptibility to microbial mineralization of complexes of humic acids and heavy metals has been confirmed. With an increase in the dose of the pollutant, the activity of humus mineralization decreases in soil without plants: at 5 MPC - by 16.7%, at 10 MPC – 12.6, at 100 MPC - by 74.7%; with plants: at 5 MPC - by 14.3%, at 10 MPC – 8.33, at 100 MPC - by 113.7%. It is also drawn attention to the fact that the activity of humus mineralization in the soil rhizosphere is lower than in the soil without plants. In our opinion, the reason for this is the presence of easily utilized substrates in the composition of plant root exudates. It makes the mineralization of hard-to-reach humus molecules inappropriate.
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