CHAPTER TWO
LITERATURE REVIEW
2.0 MEANING OF SOIL USE
Soil
is the top layer of the earths
surface in which plant can grow,
consisting of rock and mineral particles
mixed with decayed organic matter and having the capability
of retaining water
POLLUTANT ON SOIL USE
Soil
contamination or soil pollution is caused by the present of venotiotic (human
–made) chemicals or other alternation in the natural soil environment. It
typically caused by industrial activity, agricultural chemicals or improper disposal
of waste.
The
main mason why the soil become contaminated
is due to the presence of man
made waste. The waste produced from nature itself such as dead plants,
carcasses of animals and rotten fruits and vegetable only add to the fertility
of the soil. However, our waste products are full of chemicals that are not
originally found in nature and lead to soil pollution
With
the rise of concrete buildings and roads, one part of the earth that we rardy see
is the soil. It has may different names, such as dirt, mud and ground. However,
it is definitely very important to us. The plants that feed us grow in soil and
keeping it healthy very important to us.
The plants that feed us grow in soil and keeping it healthily is
essential tomaintaming a beautiful plant, however, like all other forms of
nature, soil also suffers from pollution.
The pollution of soil is a common thing
these days, and it happens due to the presence of man activities.
The waste
produced from nature itself such as dead
produced from nature itself such
as dead plants, carcasses of
animals and rotten fruits and vegetables only adds to the fertility of soil. However, our waste products are full of
chemicals that are not originally found in nature and lead to soil pollution.
MAIN CAUSES OF SOIL POLLUTION
1.
Industrial
Activity: Industrial activity has been the biggest contribution to the problem
in the last century, especially since the amount of miming and manufacturing
has increased. Most industries are dependent on extracting minerals form the
earth. Whether it is iron over or coal,
the by products are contaminated and they
are nod disposed off in a manner that can be considered safe. As a
result , the industrial waste lingers in
the soil surface for a long time and makes it
unsuitable for use
2.
Agricultural
Activities: Chemical utilization has
gone up tremendously since technology provided us with modern pesticides and
fertilizers. They are full of chemicals that are not produced in nature and
cannot be broken down by it. As a result, they seep into the ground after they
mix with water and slowly reduce the fertility of the soil. Other chemicals damage
the composition of the soil and make it easier to erode by water and air.
Plants absorb many of these pesticides and when they decompose, they cause soil
pollution since they become a part of
the land.
2.2 EFFECT OF SOIL USE TYPES ON SOIL FORMATION
The three
primary textual classes of soils are basically a product of the mineral make-up
of the soil. This further depends on the parent materials other factors that
influence soils formation includes climate, topography, animals and vegetation
(Adams et al, 1999).
On rocks and
rock debris, plant growth begins with mosses and llichens, which help to statulge
the loose materials by hiding and reducing wind speed over the surface. Furthermore,
dead plants becomes incorporated in the young soil together.
As a young soil deepens,
large are able to develop. Their roots help
stahilne the soil further
and along with carbonic acid they
produce, extend the depth of weathering
soils. Adams et al (1999) added that
although the process can take very long time, its speed in increased when the
particle becomes finer and living organisms becomes established. Finally, the
type of parent material determines the specific type of soil formed, for
instance, guards mineral forms sand soil while limestone
forms clay etc
EFFECT OF SOIL USE TYPES ON SOIL PROPERTIES
Legume
vegetation cover improve soil phosphorus. This is supported by Agboola (1975)
who reported that in Nigeria, a
single season intensive follow
with crotalorie specie, succeeded in
increasing the available phosphorus
content of a field soil from 7.8kg /ha
to 12.1kg/ha. In another experiment,
under sowing legumes in maize reduced the uptake of available phosphorus by some
50% within four growing seasons. Agbola and Feyemi (1972) concluded that the
legumes were able to keep the phosphorus in an increase as the clay content
increases. This increase depends on two mechanisms. First, bonds between the
surface of clay particles and organic matter retard the decomposition process.
Second, soils with higher clay content increase the potential for aggregate
formation.
Macro aggregates
physically protect organic matter molecules from further mineraligation caused
by microtonal attack for example, when earthworm casts and the large soils
particles they contain are split by the joint action of several factors.
(climate, plant growth and other organisms),
nutrients are released and made
available to other components of
micro-organisms under similar climate conditions, the organic matter
accumulation not only through its effect on soil texture (Mcgary, 1996). Soils developed from inherently
not material, such as basalt, are more fertile
than soils formed from granitic
material, which contains less
mineral nutrients.
EFFECT OF SOIL USE TYPE OF SOIL PH
In principle,
trees and shrubs can reduce the acidifying effect of leaching young (1982) reported that whether tree litter can be a
significant means of raising PH on
acid soil is doubtful, owing to the
order of longitude involved, expect through the
release of bases that have been accumulated dung many
years of tree growth, as in forest clearance or the (Chitemene ) system of shifting
cultivation. Young (1982) further stated that the situation is different
with respect to checking acidification. in
the first place, if the tree
compocont is employed as the means l for fertility maintenance,
then no trend towards acidification, this is in order of
0.1 PH point per year. The recycling
of bases in trees litter could quite probably be sufficient to counteract an effect of this
magnitude.
Soil PH or soil units.
The PH scale goes from 0 to 14 with PH7
as the neutral point. As the amount of
hydrogen ions in the soil increases, the soil PH decreases, thus becoming more
acidic, and l ;from PH 7 to 14, the
soil is increasingly more alkaline or basic.
According to Vermeer (1996), a soil PH
of 6 has 10 times
more hydrogen ion than a soil PH lern adrerse
to crop growth ion occur
naturally in some regions, it can also
be indued by acid rain or soil
contamination from acid or bases.
With bread et al, (1998)
supported this view by stating that the role of soil
PH is to control nutrient availability
to vegetation
The principal
macro nutrients (calcium, phosphours, nitrogen, potassium,, magnesium, sulphur) prefer neutral to
slightly alkaline soils, calcium, magnesium and
potassium are susually made available to palnts through cation
exchange surface of organic material
and clay soil surface particles
Observation
by veratna )1997) showed that addition
of one of ground plant material per
20g of soil raised the
organic content of the oil to 1.86%, PH 6.4 niitegen content 0.18%.
letroy et al (1999) reported that
while audifiation increases the
initial availability of these cutions,
the residual soil moisture
concentrations of nutrients cations could
fall to alarmingly low levels
after initial nutrient up take moreover there is one simple
relationship of PH to nutrient availability because of the complex combination of soil types,
soil moisture regimes and
meterological factors. Excess of
organic matter can have a lowering
effect on the PH value of
most soils (mbagwu and
piccolo, 1990)
EFFECT OF SOIL TYPE IN SOIL ORGANIC MATTER
When plant residues are returned to the soil, various organic
compounds undergo decomposition. Decomposition is a biology process that
includes the physicial breakdown and biochemical transformation of complex organic molecules of dead material into simpler
organic and inorganic mdecules.
Decomposition
oforganic matter is largely a biological process that occurs naturally. Its speed is determineby three major
factors soils organisms, the physical envieornment and the quantity
of the organic matter (Brussaard, 1994) . in
the decomposition process, different product are released, carbon compounds
Successive
decomposition of dead material and modified orgnic matter results in the
formation of a more complex organic
matter called l humus. This process is called humification. Humus
affect soil properties . as it slowly decomposes, it colours the soil
darker, increases soil aggregation and
aggregate stability, increases the CES (The
ability to attract and retain nutrients), and
contributes N,P and other
nutrients. Soil organisms, including
micro –organisms, use soil organic
matter as food. As they breakdown the organic matter, excess
nutrients (N,P and S) are released into the soil in forms that
plant can use. This released by
micro-organisms are also soil organic
matter. This waste materials is less
decomposable than l the
original plant and aimal
materials, but it can be used by a large number of organisms
(levelle and spain, 2001). By breaking
down carbon structures and rebuilding
new ones or storing the C into their
own biomass, soil biota plays
the most important role in nutrient cycling
process and, thus, in the ability
of a soil to provides the crop with sufficient
nutrients to harvest a healthy product
(FAO, 2002). The
organic matter content,
especially the more stable humus, increases
the capacity to store water and store (Sequester) from the atmosphere (Linn and Dovan, 1984), organic matter serves as a nuturient
store from which basic cations are slowly decomposes, it colours the soil darker, increase soil aggregation and
aggregate stability, increases the CEC
(The ability to attract and retain
nutrients), and contributes N,P and other nutrients
Soil
organisms, including micro organisms,
are soil orgnic matter as
food. As they break down the organic matter, excess nutrients (N, P and
S) are released into the soil in form that plant can use. This release
process is called mineralization.
The waste material is less
decomposable than the original plant and animal material, but it can be
used by a large number of o0rgnisms (Lavelle
and Spain, 2001). By breaking down caibon structures and
rebuilding new one sor storing the C into
their own biomass, soil biota
plays the most important role in
nutrient cycling process and, thus, in
the ability of a soil to provide the
crop with sufficient nutirients to hearvest a helthy product (FAO
2002). The organic matter content, especially the more stable humus, increases
the capacity to store water and store (Sequester ) from the
atmosphere (LINN AND Doran, 1984).
Organic matter serves as a
nutrient store from which basic cations
are slowly released into the soil. It
account for over 80% cation
exchange capcity (CEC) OF THE HUMINAL TROPICALsoil (AGBOLA AND FAGHENRO 1985). The type of vegetation determines the type of cover and
quality of organic matter in the soil.
Legume according to Brady and Weil
(1999), makes riche organic matter
than grasses and gmelina covers.
Mineral colloid and organic matter constitute
the soil exchange complex being negatively charged
(Nwingyi, 1977).
According to Ekpe (2002), Orgaic matter is
a store house for plant nutrients is also
the cementing in soil
structure and aggregate
formation. Ekpe (2002) also noted that
soil organic matter help to
improve the soil water holding capacity and hydraulic conductivity.
Excess of organic matter can have
a lowering effect of the PH value of most
soils
Furthermore,
with time iron oxides of the soil are
soluvilized and leached specially in the
tropic where activities of micro
organism are high
EFFECT
OF SOIL USE TYPES ON EXCHANGE BASE
Organic mater
from vegetation cover contain
exchangeable bases in varied quantities.
These mineral nutrients are
important components of the
vegetation bio-system which it releases
to the soil on death and decomposition.
The efficiency of the use of
vegetation to improve on soil properties is dependent on the
stage of
growth of the vegetation. In legume, maximus effect is achieved at flowering stage while in grasses it is somewhat earlier (MULLERN SAMANN AND KOTSCHI 1994) Gmelina cover is
reported to be effective only when it
is about 12 month old.
The
exchangeable incorporated in soil by organic
matter resulting form vegetation cover are similar to those from any other form of organic matter. The
exchangeable bases content
of soil differ depending on the parent material
vegetation cover, cropping
history and soil management practices employed
finally, economic justification
of the use of organic fertilizer lies in
the necessary to cope with
prevalent increase in the cost of mineral fertilizer and reduction
in the waste of nutrient result from on
under utilization of organic residue
(FAO 2002).
EFFECT
OF ORGANIC MATTER ON SOIL CHEMICAL PROPERTIES
organic
matter affect both the chemical and physical properties of the soil and its
overall health (FAO, 2000) properties influenced
by organic matter include: soil
structure, moisture holding capacity, diversity and captivity of
soil organisms, both those that are beneficial and harmful to crop
production and nutrient availability (Vieria and Van Wambeke 2002).
However,
it also influence the effect of chemical
amendments, fertilizers pesticides and herbicides. Organic matter has been known to be a major natural source of both macro and
micronutrient. Organic matter has many benefits in the and
porosity and increase in the
number of macropores, and thus to greater infiltration rates. Increased
levels of organic mater and
associated soil fauna lead to greater pore space with the immediate result that water
infiltrates more readuy biotur
batting activities of earth worms and other macro organism and channels left
in the soil by decayed plant roots. Rainwater infiltration increased from 20mm/h under conventional tillage to
45mm in under no tillage’s. Over a long period, improved organic matter promotes good soil
structure and macroporsity , water
infiltrates easily similar to
forest soils
In
addition organic matter contribute to
the stagility of soil aggregates and
pores through the bounding or adhesion
properties of organic matrials,
such as
bacterial waste products,
organic gls, fungal hyphas and worm secreteions
and casts (tate et al, 2004)
Moreover
organic matter intimately mixed with mineral
soil materials has a considerable influence in increasing moisture holding capacity. Especially the
topsoil, where the organic matter
stoe form which basic cations
are slowly released into the soil. Ortanic matter accounts for over 80% cation
exchange capacity (CEC) of the humed tropical soils (Agboola and
faghenro, 1985) . the
quantity of organic matter in the soil at any given time is an
indication of the capacity of the soil to renew the supply when the
nutrient in solution have
been utilized. Mineral colloid
and organic matter constitute and
soil exchange complex, being negatively
charged (Nwiniyi, 1977) organic
matter contributes very significantly to
the soil cation exchange capacity.
Through exchange processes plant can take up exchangeable
cation which are important
as nutrient (Wezel et al 2000)
Nitrogen
is one of the macro nutrient needed for
maximum growth production and
yield of crop. Nitrogen is very
important for protein synthesis and
nuclicic acids sysnthesis. Nitrogen is one of the essential elements. It is
utilized by plant for making proteins and chlorophy (Watkins et al 2006). Overation by agbooola (1982) showed that organisms cannot use gaseous nitrogen
except some few
species of bacteria and blue green alge that are capable of utilizing
the gaseous nitrogen form the soil. Gaseous nitrogen bacterial called
Azotobacter Clostridum and Rhospirllum living in the soil, nitrogen fixing bacteria (Sysmbiotic bacteria), the species
of phizobuim such as R
leguminosarium have symbiotic
association with roots of
some leguminous plant such as groundnut , beans and crotalaria, furthermore, these sysmbiotic
bacteria enter the root hair walls of
the lequmes and multiply thus causing swellings or nodules in the infected
cells karl and
Johannes (1994) noted that the
most glaring effect of grass cultivation on nutirient economy of the soil is ntitrogen enrichment. Gasser (1964) asserted that organic nitrogen not only increase
tutrifying activities of
micro organism but also decreases nitrogen losses by increasing
cation exchange capacity. Crop reside added to the
soil fixed nitrogen in soil during the early state of decomposition of solube carbohydrate. This is that
succeeding crop suffered. Nitro
deficiency (Agboola, 1982.
Ahmed et al, 1969) and Azevedo and stout, 1979) . they recommended supplemental
nigtrogen to achieve a C.N
ration of less than
15:1 this organic
source according to their
report could also come
from animal droppings .
3.
Waste disposal: finally, a growing
cause for concern is how we dispose of our waste while industrial waste is another way in
which we are adding to the
population every human
produces a certain amount of peronsal waste products by way or urine
and feces
While much of it
mores into the sewer the system, there is
also a large amount that is
dumped directly into landfills in the form of diapers. Even the swer system
ends at the landfill, where the
biological waste pollutes the soil and water. This is because our bodies are full of toxins
and chemicals which are now seeping
into the land and
causing pollution of soil
4.
Accidental
oil spills: Oil
leaks can happened during storage
and transport of chemicals. This can be
seen at most of the fuel stations/. The
chemicals present in the fuel deteriorates
the quality of soil and make them unsuitable for cultivation. These chemicals can enter
into the ground water through soil and
make the water undrinkable
5.
Acid
rain: acid rain is caused when
pollutants present in the air mixes up with
rain and fall back on the ground.
The polluted water could
dissolve away some of the important nutrients found in soil and change the structure of the soil
2.1 EFFECT OF POLLUTANT ON SOIL
USE
1. On health of human
Considering how soil is the reason we are able to
sustain ourselves, the contamination of
it has maor consequences on our health. Crops and plants grown on polluted soil absorb much of the
pollution and then pass these on to us.
This could explain the
suddn surge in small and
terminal illnesses long term exposure to
such soil can affect the gentic make up
of the body causing congential illnesses
and chronic health problems that
cannot be cured easily. In fact, it can
sicken the livestock to a considerable
extent and cause food poisioning
over a long period of time . the soil polluation can even bad to wide spread famines if the plants are unable to grow in
it
2. On growth of plants: the ecological
balance of any system gets affected due
to the widespread contamination to the
soil. Most plants are unable to adapt when the chemistry of the soil changes so radically
in a short period of time. Fungi
and bacteria found in the soil that bind
together begin to decline, which creates an additional problem on soil erosion
The fertility slowly diminishes,
making land unsuitable for
agriculture and any local
vegetation to survive. The soil pollution causes large tracts
of land to become hazardous
to health unlike deserts, which
are suitable for its native
vegetation, such land cannot
support most form of life.
3. decreased soil fertility
: the toxic chemicals l present in the soil cand
decrease soil fertility and therefore decrease in the yield then contaminated
soil is then used to produce fruits and vegetables which lacks
quality ad nutrients and may contain some poisonous substance to
cause serious health problems in
people consuming them.