Agriculture Reference
In-Depth Information
Figure 3. Effect of mulches on the amount of exchange bases in the plow horizon.
The reduction in the soil acidity is explained by the faintly alkaline reaction of this
ameliorant (рН KCI  7.4) and a very high base saturation. Similar effect of bentonite clay on
acid soils was observed by other researchers (Sharafeeva, 1980).
Another positive effect of bentonite clay is the increase in the amount of exchange bases
from 1-2% to 18% compared with the control (without mulch). It is remarkable that the
positive effect maintained throughout the five years of observation, being 6.7% on average.
This was possible due to the high content of montmorillonite, a mineral with a very high
cation exchange capacity of 90-120g mmol/100g of the mineral.
The effect of peat on physical and chemical properties of soil is determined by its origin,
botanical composition and decomposition degree. Usually peat is acidic, due to its chemical
composition, i. e. the high content of specific and nonspecific organic acids and the presence
of labile aluminum. The amount of hydrolytic acidity in peat varies widely from 1-2 to 150-
160g mmol/100g BDH. The most acidic is high-moor peat. Its application without prior
liming can cause soil acidification and reduce crop yields. In low-moor peat, organic acids are
largely neutralized by calcium and other base cations. Therefore the acid-alkaline balance of
the soil may even shift to the alkaline side. In our experiments we tested low-moor peat with
the acidity of 6.4 рН KCI units. Mixing it with the soil layer of 0-5 cm at the proportion of 40
t/ha led to a slight decrease in acidity of the plow horizon, but this effect was not stable and
was observed mainly during the first two years after the application.
The effect of peat on the amount of exchangeable bases was more apparent. Its
incorporation in the soil layer of 0-5 cm increased this indictor to 1-2% ... 13-15% compared
with the control, and the average for the five years of observation was 6.7% (Figure 3). This
is due to the fact that peat is a natural ion-exchange material with high absorption capacity,
which consists of the exchange, chemical, physical, mechanical and biological absorption
capacity.
The exchange capacity is determined by the chemical nature of peat and, above all, the
content of functional groups. It depends on the decomposition degree of peat and the content
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