which is known to be characteristic of soils with humus-accumulative type of soil
formation.
By comparing the data of granulometric test of black soil under forest cultures,
arable variants and herbs, we see that under the forest crowns, the amount of dust
fraction (0.005-0.001) is somewhat higher in the upper horizons, which can be possibly
associated with atmosphere dust fall when the wind speed over the forest decreases.
Consequently, the granulometric composition of all variants of the studied black
soils has a general pattern: it practically does not change on the soil profile, which is
characteristic for the humus-accumulative process of soil formation.
The content of silt particles found in the microaggregate soil analysis, in
comparison to the data of their granulometric analysis, is very low. It fluctuates in the
upper (0-20 cm) layer of soil under the tree cultures from 2.5 to 2.4%, and under the
arable soil – 3, 3%, which is less than the average silt content in granulometric analysis
by more than 10 times.
An example of a possible total expression of black soils' microagregation degree
under forest plantations may be a dispersion coefficient, which expresses the potential
ability of soils to structure’s formation, calculated by Kachynsky method [10]. The
dispersion coefficient as an indicator of soil potential capacity for structural formation
is relatively low in black soils under forest plantations: 7.4-8.0% in the upper (0-20
cm) layer, 7.3-7.4% under herbs, 9.2% in arable black soils. This allows suggesting
that black soils under artificial forest plantations and under herbal vegetation have a
higher potential for structural formation than arable black soils. The bulk of mechanical
elements of forest soils are in an aggregated state.
Data on the determination of the structural and aggregate composition of studied
black soils show that the structure of chernozemic soils under forest plantations is very
high; the structuredness coefficient varies within 3.80-9.00 versus 1.66 for arable land's
black soils.
Oak
Birch tree
Pine
Modrida
Glade
Fallow
Arable
land
Figure 1. Dispersion factor by Kachynsky
Source: Developed by the authors
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