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Aeration
Can Improve The Physical properties of soil
Texture
Soil
texture refers to the relative amounts of inorganic
particles i.e. Sand, Silt and Clay. Sand grains are large
and coarse, clay particles are vary fine and smooth, and
silt particles intermediate.
Structure
The
way in which soil particles are grouped or bound together to
form lumps or aggregates is known as soil structure. There
are two main types of soil structure, (10) single grained and
(2) compound structure. Soil structure can be modified by
adopting various soil management practices including aeration,
tillage, crop rotation, irrigation, drainage etc.
Density
The
density of soil can be expressed in two ways. (1) The
density of solid (particle density), particles of the soil
and (2) the density of the whole (Bulk density) soil that is
inclusive of pore space. Generally soils with low bulk
density have better physical condition than those with
higher bulk densities. Texture and structure of a soil, its
total pore space and organic matter content are all related
to bulk densities. Soil density can be modified with aeration.
Porosity
Between
the soil particles there are empty spaces which are occupied
by air and water and are termed as pore spaces. Pore spaces
between the aggregates of soil particles are macro pores and
those between the individual particles of the aggregates are
micro pores. Sandy soils have a higher percentage of macro
pores. Typically, sandy soils never become water logged and
allow water to percolate downward more rapidly than clay
soils. Typically, moisture content in sandy soils is
relatively low when compared to clay soils.
Clay
soils contain a higher percentage micro pores when compared
to sandy soils. Clay soils are more susceptible to water
logging which can adversely effect root respiration and
microbial activity. A proper balance between the macro and
micro pores can be maintain by timely aeration.
Colour
Soil
color is helpful in determining soil properties. A dark
brown or black colored soil indicates its high organic
matter content and fertility. A red or yellowish soil shows
good aeration and proper drainage. A white color, resulting
from the accumulation of salts of alkali indicates
deterioration of soil fertility and its unsuitability for
normal growth of many crops
Soil
temperature and plant growth
Soil micro-organisms show maximum growth and activity at
optimum soil temperature range. All crops practically slow
down their growth below the temperature of about 90C
and above the temperature of about 500 C. The
biological processes for nutrient transformations and
nutrient availability are controlled by soil temperature and
soil moisture. Soil temperature has a profound influence on
seed germination, root and shoot growth, and nutrient uptake
and crop growth. Seeds do not germinate below or above a
certain range of temperature but Micro-organisms functioning
in the soil are very active while a certain range of
temperature, which is about 270 to 320C.
It is necessary to know whether the soil temperature is
helpful to the activities of plants and micro-organisms and
the temperature could be suitably controlled and modified.
The various factors that control the soil temperature are
soil moisture, soil colour, slope of the land, vegetative
cover and general soil tilth. Aeration
can be used to control soil temperature, regulate soil moisture,
improve drainage, stimulate microbial activity and improve
overall soil tilth.
Biological
properties of soil
A
variety of organisms inhabit the soil. They decompose
organic matter, fix atmospheric nitrogen, cause
denitrification etc. Specific groups of organisms are
responsible for specific activities in the soil. Such
activities may be beneficial or harmful to the crop or its
yield potential.
Bacteria
Bacteria
are generally confined to the 20 to 30 cm. layer and
work best when there is (1) good aeration, a neutral
reaction, soil moisture content at about half of the soil's
water holding capacity and temperature between 250 c
and 380 c.
Fungi
These
organisms produce microscopic threads called mycelia and are
found in the organic matter of plant roots. Fungi help in
breaking down the somewhat resistant parts of the organic
matter like cellulose, lignin, gums etc. A large part of
slowly decomposing soil humus is made up of the dead remains
of fungi.
Actinomycetes
They
can grow in deeper layers even under dry conditions. Their
main function lies in decomposing the resistant parts of
organic matter like cellulose.
Algae
They
are microscopic or very minute sized plants having
chlorophyll and are usually found on the surface of wet
soils. They help in adding organic matter to soil, improving
the soil aeration and fixing atmospheric nitrogen.
Texture
and other soil properties and plant growth
Many
of the important soil properties are related to texture.
Clayey soils show high water holding capacity, high
plasticity, and stickiness and swelling whereas sandy soils
are conspicuous by the absence of these properties. The most
important way in which soil texture affects plant growth is
water and with it the nutrient supply. The available water
holding capacity of soil is related to soil texture. Timely aeration
can improve Soil texture improved water holding capacity.
Soil
structure and plant growth
Soil
structure influences plant growth rather indirectly. The
pores are the controlling factors governing water, air and
temperature in soil, which in turn, govern plant growth. One
of the best e.g. of the effect of soil structure on plant
growth is the emergence of seedlings in the seedbed. The
seedlings are very sensitive to soil physical condition so
that there should not be any hindrance to the emergence of
tender seedlings and there should be optimum soil water and
soil aeration. The soil in the seedbed should have a
crumb structure so that the roots of the seedling can
penetrate it easily. The hard compact layer impedes root
growth.
Soil
water
Water
is essential for plant growth. Soil is capable of being a
storehouse of water and becoming the main source of water
for land plants. Soil water plays a significant role in
several natural processes- evaporation, infiltration and
drainage of water, diffusion of gases, conduction of heat,
and movement of salts and nutrients are all dependent upon
the amount of water present in soil. Plants
meet their water requirement from water stored in soil. Soil
moisture can be improved with aeration.
Soil
Aeration and plant growth
Oxygen
is required by microbe and plants for respiration. Oxygen
taken up and carbon dioxide evolved are stoichiometric.
Under anaerobic conditions, gaseous carbon compounds other
than carbon dioxide are evolved. Root elongation is
particularly sensitive to aeration. Oxygen deficiency
disturbs metabolic processes in plants, resulting in the
accumulation of toxic substances in plants and low uptake of
nutrients.
Soil
compaction
Soil
compaction is the process of increasing dry bulk density of
soil and reducing pore space by expulsion of air through
applied pressure on a soil body. Soil compaction is a
limiting factor in seed germination, water transmission and
aeration. Timely aeration and the incorporation of
biologicals can prevent soil compaction.
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