ESTONIAN ENVIRONMENTAL REVIEW 2009

7.1.2. Soil formation
Soil is created as a result of long-term natural processes
that take place over the long term. The primary
factors that shape the soil are climate, the parent material
(mineral or rock on which the mineral fraction of soils is
based), the relief of the surface of the land, the age of the
soil and the time spent on soil formation and the action
of a number of plants and micro- and macroorganisms.
The mutual actions of soil and plants are the driving
force behind soil formation – naturally occurring plants
colonize places that are suitable for their growth and
shape surface soil into contours that are suitable for their
growth. Soil plays an important part in delivering the
water and nutrients that plants need. Soil is inhabited
by millions of microorganisms (bacteria, fungi etc) and
macroorganisms (earthworms, insects, arachnids etc),
which, among many other functions, convert nutrients
into forms available to plants, thus taking part actively in
soil formation. In the course of the biochemical processes,
new and more complicated forms of organic matter are
created – such as humus, the embodiment of soil fertility.
Soil comprises not only the humus-rich topsoil – dark in
colour from organic matter – but also includes layers to
a depth of several metres, to which plant roots extend,
where soil organisms also are active and where the effects
of humus can be noted.
Estonian soil is shaped by the
following key processes:
• topsoil formation – formation of humus and
humus layer; occurs in nearly all soils;
• clay formation and accumulation – upon
weathering, clay minerals are created and form
complex bonds with the humus in the soil, and the
soil profile or part of the soil profile becomes
enriched with clay particles;
• lessivation – migration of clay particles from upper
levels of the soil to lower levels through the action
of water and gravity;
• pseudopodzolisation – temporary combined action
of surface water and precipitation and lessivation at
the boundary of layers with a different soil texture
or in the uppermost layers of clay and clay-sand;
• podzolisation – decomposition of minerals and
organic matter in the soil due to the action of
humic acids and elluviation of products of the
decomposition from the soil;
• gleying – creation of bluish or greenish-grey
patches and layers in anaerobic or waterlogged
conditions, as the oxygen necessary for converting
organic matter is extracted from mineral com
pounds. Fe 3+ compounds are reduced to Fe 2+
compounds;
• peat formation – seen in soils where organic
matter does not decompose due to waterlogged
conditions.
7.1.3. Characteristics of Estonian soils
The most important characteristics of soils are the
soil type, texture type (ratio of clay to sand), structural
grade, acidity, humus content, thickness of the topsoil,
mineral nutrient content, existence of water, air and
warmth and soil biota.
In Estonia, the primary factors responsible for distinctions
between soils are the chemical composition of the
source mineral (calcareousness, nutrient supply), soil
structural type, rockiness and water conditions (droughtsusceptible
or dry, moist, excessively moist).
The following characteristics describe Estonian soil:
• great variability of the soil;
• extensive range of calcareous soils;
• high percentage of soils that have
excessive moisture;
• occurrence of limestone rock in the soil
profile and high rockiness of soils.
The classification of Estonian soils distinguishes
between around a dozen soil types and within these,
nearly a hundred subcategories of soil. The most common
soils are calcareous rendzinas, cambisols (typical brown
soils), and podzolic (lessive) soils, pseudopodzolic soils,
sod-podzolic soils, podzols, gleyed soils (moist soils),
gleysols (wet soils) and histosols (map 7.1).
Soil maps on very different scales have been prepared
for Estonia and a number of them have now been
updated. The soil map in this publication is based on the
1: 1 000 000 scale Estonian soil map. Perhaps the most
valuable resource for ordinary users is the 1:10,000 digital
soil map compiled in 1997–2001, which along with the
corresponding database is available on the Land Board
website (www.maaamet.ee). The digital map is a good
way above all for farmers to learn about their soils and
use them accordingly.
Land use is determined primarily by soil fertility. As
a result, more fertile land is in agricultural use and less
fertile land is used in forestry. Often settlements and
technical works are built on more productive soils as
human settlement develop on better lands.
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