The content of agronomically valuable aggregates (the sum of structural fractions
from 1 to 10 mm in diameter at dry sieving) for the upper (0-20 cm) soil layer is 54.5-
87.1%. In the soil under forest cultures, the content of agronomically valuable
aggregates is as follows: under oak – 71.9%, under birch – 73.6%, under larch – 64.0%;
under the herbal vegetation – 73.2% (meadow), 87.0% – rotation field area, and for
comparison: in the soil of arable land it is 57.3%, which testifies to better structure of
black soils under afforestation and herbs.
In regards to content of water-resistant units (fraction 1-10 mm), the upper
horizons of soils under forest plantations and herbs contain a sufficiently large number
– 48.4-66.4% of these aggregates, where under arable soil there is 41.2%. Structure's
dispersion (aggregates lesser than 0.25 mm) in soils under the forest is only 3.2-12.1%
versus 36% in the arable ones.
Table 1 Structural and aggregate composition of typical black soils under
different vegetation cover
Opportunities
for the
experiment
Dry sieving
Wet sieving
Water
-r
es
is
ta
n
t uni
ts
, %
C
ont
ent
of a
grono
m
ic
al
ly
va
lua
bl
e a
ggr
ega
te
s, %
W
at
er r
es
is
ta
n
ce
cri
te
ri
on
, %
S
truc
ture
dne
ss
coe
ffi
ci
en
t
>10
10
-5
5
-1
1
-0
.25
<0
.25
>1
1
-0
.25
<0
.25
Oak
17.48 28.13 43.76 7.39 3.23 24.50 38.23 37.27 62.73 71.89 19.33
3.83
Birch tree
3.17 11.54 62.05 16.40 6.83 20.85 33.87 45.28 54.72 73.59 48.44
8.99
Pine
4.96 12.32 42.19 28.42 12.12 8.17 45.40 46.43 53.57 54.51 62.59
4.86
Modrida
5.62 12.05 51.97 19.12 11.25 6.67 41.70 51.63 48.37 64.02 45.85
4.93
Glade
4.46 16.21 56.98 14.85 7.50 17.10 45.80 37.10 62.90 73.19 32.42
7.36
Fallow
1.83 18.35 68.71 8.33 2.78 46.25 20.14 33.61 66.39 87.06 41.36 20.71
Arable land
1.73 22.77 34.52 5.12 35.87 6.80 34.40 58.80 41.20 57.29 14.88
1.66
Therefore, microaggregate and structural state of deep typical black soils
improves under the crowns of forest plantations, more water-resistant structural units
are formed. As well there is significant improvement of structural composition of black
soils under forest plantations (oak, birch, larch, pine) (Fegeliar structural factor: 92.0-
93.0%) and destruction (dispersion) of the structure at tilling (90.8%).
Thus, well-organized soil with water-resistant structural units is formed in typical
black soils under crowns of tree vegetation of cultural ecosystems (birch, oak, larch,
pine).
Granulometric composition of black soil is characterized by an increased number
of fractions of 0.01 mm and can be classified as heavy-loam soil.
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