ABSTRACT
This study evaluated microbiologically, the effect of soil erosion on microbial communities based on soil microbial load. In the course of this study, soil samples were obtained from three (3) different erosion sites Umuobia, Amuzukwu and Isieke-Ibeku, with three (3) soil samples obtained in each erosion site from the Upper Slope, Middle Slope and Lower Slope and in addition to them, two other soil samples (Agricultural soil and Trampled soil) were obtained and used as controls. From this study, the mean microbial counts from the samples analyzed revealed that Agricultural soil had the highest bacterial count at 1.37×105, followed by the Lower Slope soil samples of the eroded sites, and the least bacterial count was recorded in the Middle Slope of the eroded soil samples. The total fungal plate count investigated revealed Agricultural soil as having the highest fungal count (1.26×105) and the Middle Slope of eroded soil samples as having the least fungal count (0.00×105). Bacterial strains were isolated using the spread plate techniques and were identified using colonial morphology, Gram staining reaction, biochemical and motility tests which revealed the major bacterial isolates to be Bacillus species, Pseudomonas species, Actinomycetes species, Staphylococcus species and Escherichia coli while microscopic and colonial morphology revealed the fungal isolates to be Aspergillus niger, Fusarium solani, Fusarium oxysporum. The percentage occurrence of bacterial isolates showed Bacillus species as the most frequently occurring at 6(30%) while percentage occurrence of fungal isolates revealed Aspergillus niger as the highest occurring fungi at 5(45.5%).
TABLE
OF CONTENTS
Title Page i
Certification ii
Dedication iii
Acknowledgements iv
Table of Contents v
List of Tables viii
Abstract ix
1.0
CHAPTER ONE 1.1 INTRODUCTION 1
1.1.1
Soil Erosion 1
1.2
Types of Soil Erosion 3
1.2.1 Water Erosion 3
1.2.2 Splash Erosion 3 1.2.3 Rill Erosion 3
1.2.4 Gully Erosion 4
1.2.5 Wind Erosion 4
1.3 Effects of Soil Erosion 4
1.4 Advantages and Disadvantages of
Soil Erosion 6
1.5 Factors that Contribute to Soil
Erosion 7
1.5.1 Climatic Factors 7
1.5.2 Soil Nature 7
1.5.3 Topography 7
1.5.4 Human Factors 8
1.5.5 Vegetation 8
1.6 Aim and Objectives of the Study 9
1.6.1 Objectives of the Study 9
2.0 CHAPTER TWO 10
2.1 LITERATURE REVIEW 10
2.1.1 Effect of Soil Erosion on Soil Microorganisms 10
2.2 Microorganisms Found in Soils 12
2.2.1 Soil Bacteria 13
2.2.2 Soil Archaea 14
2.2.3 Soil Fungi 14
2.3 Microorganisms Isolated from Eroded
Soils 15
3.0 CHAPTER THREE 18
3.1 MATERIALS AND
METHOD 18
3.1.1 Study Area 18
3.2 Soil Sample
Collection 18
3.3 Materials Used 19
3.4 Preparation of Media 19
3.5 Enumeration of Microorganisms from
Soil Samples 19
3.5.1 Serial Dilution-Agar Plating Method 19
3.6 Purification of Bacterial
Cultures 20
3.7 Characterization and Identification
of Bacterial 20
Isolates
3.7.1 Gram Staining
20
3.7.2 Biochemical Tests 21
3.7.2.1 Coagulase test 21
3.7.2.2 Catalase production test 21
3.7.2.3 Citrate utilization test
21
3.7.2.4 Indole test 21
3.7.2.5 Carbohydrate fermentation test 22
3.7.2.6 Motility test 22
3.7.2.7 Hydrogen sulphide production test 22
3.7.2.8 Voges proskauer test Methyl red test 23
3.7.2.10 Oxidase test 23
3.8 Purification of Fungal Cultures 23
3.9 Identification of Fungal Isolates 24
3.9.1 Macroscopic Examination 24
3.9.2 Microscopic Examination 24
4.0 CHAPTER FOUR 25
4. 1 RESULTS 25
5.0 CHAPTER FIVE 32
5.1 DISCUSSION, CONCLUSION AND
RECOMMENDATION 32
5.1.1 Discussion 32
5.1.2 Conclusion 36
5.1.3 Recommendation
37
References
Appendix I
Appendix II
LIST OF TABLES
S/N TITLE PAGE NUMBER
1 Mean
Microbial Counts from Samples 27
2 Results from Biochemical Tests 28
3 Identification
of Fungi Isolated 29
4 Percentage
Occurrence of Bacterial Isolates 30
5 Percentage
Occurrence of Fungal Isolates 31
1.0 CHAPTER
ONE
1.1
INTRODUCTION
1.1.1 Soil Erosion
Soil erosion is the
detachment and movement of soil material. It can also be referred to the
wearing away of a field's topsoil by the natural physical forces of water and
wind. Soil erosion may be a slow process that continues relatively unnoticed,
or it may occur at an alarming rate causing serious loss of topsoil. Soil
erosion is the most widespread form of soil degradation. Soil degradation
refers to reduced soil fertility due to changes in physical, chemical and
biological soil properties caused by erosion (Carpenter et al., 2001). Soil erosion is considered to be a major
environmental problem since it seriously threatens natural resources and the
environment (Rahman et al., 2009).
Soil erosion, as it
affects man and its environment, is natural and as old as the earth itself
(OMAFRA Staff, 2003). It is seen as the gradual washing away of soil through
the agents of denudation which include, wind, water and man. These denudating
agents loose, wear away, dislodge, transport and deposit wear off soil
particles and nutrients in another location (Abegunde, et al., 2003). Soil erosion remains the world’s biggest
environmental problem, threatening sustainability of both plant and animal in
the world. Over 65 percent of the soil on earth is said to have displayed
degradation phenomena as a result of soil erosion, salinity and desertification
(Okin, 2002). From time immemorial, soil erosion has been a naturally occurring
process (OMAFRA Staff, 2003). At present, it is the single most important
environmental degradation problem in the developing world (Ananda and Herath, 2003),
especially the tropics (Hanyona, 2001). United Nations (UN) Convention to
Combat Land Degradation (CCD) opines that soil erosion automatically results in
reduction or loss of the biological and economic productivity and complexity of
terrestrial ecosystems, including soil nutrients, vegetation, other biota, and
the ecological processes that operate therein (Claassen, 2004).
In another dimension, Scherr
and Yadav argue that by this year 2020, soil erosion may pose a serious threat
to food production and rural (as well urban) livelihoods particularly in poor
and densely populated areas of the developing world. They further advocate for
policies that would encourage soil retention strategies, land improving
investments and better land management if developing countries are to
sustainability meet the food needs of their populations, preserve non renewable
natural resources and hand over their soils to future generations. Significant
in this is that when soil gives away its fertility, human beings lose their
fundamental living source they rely on. This is why soil erosion has been
identified as the direct cause of environmental deterioration and poverty in
many parts of the world (Beijing Time, 2002).
Soil erosion has worsened
human civilization and the quest for better live by man. It is either caused by
natural agents or induced as a result socio-economic development over the
years. The eroded material from soil erosion cause both on-site and off-site
effects which are detrimental to both flora and fauna. The effects could be
exacerbated by inter and intra reactions within the ecosystem. In areas with
expanding population, agricultural production, construction and urbanization as
well as human activities, soil erosion is a major problem (Leh, et al., 2011). Soil erosion is usually
characterized by three actions, involving soil loosening, transport, and
deposition. These processes usually result in the relocation of the top soil
which is rich in organics, nutrients, and soil life elsewhere on-site where it
builds up over time or is transported offsite where it accumulates in drainage
channels. It is usually severe on unprotected sloppy areas (Shi et al., 2012).
1.2 TYPES OF SOIL
EROSION
Basically, rainfall, surface
runoff which may result from rain fall and wind results in various types of
soil erosion. They may include the following:
1.2.1 Water Erosion
Water erosion has been the
most widely studied type of erosion, and is arguably the one that affects the
greatest land area. In water erosion, the detachment of soil from the soil mass
occurs in two ways: from the effects of raindrop splash on the soil surface,
and from forces exerted by water flowing across the surface (runoff). Transport
of the detached soil by flowing water first occurs in thin sheets of runoff
flowing over the surface (sheet erosion). Often the surface runoff becomes
concentrated in small channels (rill erosion) or deeper incisions (gully
erosion); in both of these types of channels the erosive power of the flow is
greatly magnified. The rills and gullies resulting from water erosion are some
of the most visible signs of erosion operating in the landscape.
1.2.2 Splash Erosion
Splash erosion is usually the
first stage of the erosion process. It occurs when raindrops hit bare soil. The
explosive impact breaks up soil aggregates so that individual soil particles
are splashed onto the soil surface. Angulo-Martínez et al. (2012) defined splash erosion as a complex process that
causes the detachment of soil particles by raindrop impacts on the soil surface
followed by short-distance transport of detached particles. Splash erosion can
displace soil particles as high as 1.5 m vertically (Ryzak et al., 2015), and can reach horizontal distances of more than 5 m
with the help of the wind (Erpul et al.,
2009).
1.2.3 Rill Erosion
Rills are shallow drainage
lines less than 30cm deep (Cerdan et al.,
2002). It is soil detachment and transport by water flowing in channels less
than 0.3 m deep (Castillo and Gomez, 2016). Usually, rills are eroded channels
that can be filled in by normal tillage operations. They develop when surface
water concentrates in depressions or low points through paddocks and erodes the
soil (Govers et al., 2007). Rill
erosion is common in bare agricultural land, particularly overgrazed land, and
in freshly cultivated soil where the soil structure has been loosened. The
rills can usually be removed with farm machinery. Rill erosion is often
described as the intermediate stage between sheet erosion and gully erosion
(Romero et al., 2007).
1.2.4 Gully Erosion
Gullies are channels
deeper than 30cm that cannot be removed by normal cultivation. The main causes
of are allegedly global climate changes and anthropogenic pressure (Torri and
Poesen, 2014). However, experimental studies on gully erosion commonly lacked
the ampleness of those dedicated to surface sheet erosion, even in Europe
(Poesen et al., 2006). Gully erosion
results from soil detachment and transport by water flowing in channels greater
than 0.3 m deep (Castillo and Gomez, 2016).
1.2.5 Wind Erosion
Wind erosion occurs
primarily in arid and semi-arid environments and is the major form of erosion
in, for example, the Near East and North Africa region. In wind erosion, the
detachment of the soil occurs because of the forces exerted by the wind on the
soil surface, and because of the effect of detached soil bouncing off the soil
surface downwind of the point of initial detachment (saltation). Transport of
the soil occurs within the wind stream, and the size of the grains being
transported largely dictates the transport distance. In some cases the
transport distance may be hundreds of kilometres from the point of detachment
(FAO, 2011).
1.3 EFFECTS OF SOIL
EROSION
The main on-site impact of
soil erosion is the reduction in soil quality which results from the loss of
the nutrient rich upper layers of the soil, and the reduced water-holding
capacity of many eroded soils. The breakdown of aggregates and the removal of
smaller particles or entire layers of soil or organic matter can weaken the
structure and even change the texture. Textural changes can in turn affect the
water-holding capacity of the soil, making it more susceptible to extreme
conditions such as drought. In addition to its on-site effects, the soil that
is detached by accelerated water or wind erosion may be transported to
considerable distances. This gives rise to off-site problems. Water erosion’s
main off-site effect is the movement of sediment and agricultural pollutants
into watercourses. This can lead to the silting-up of dams, disruption of the
ecosystems of lakes, and contamination of drinking water. In some cases,
increased downstream flooding may also occur due to the reduced
capacity of eroded soil to
absorb water. Sediment can accumulate on down-slope and contribute to road
damage (Balasubramanian, 2017).
Soil erosion mechanisms
have an effect on how much water the soil can hold, how rapidly water flows
over the soil, and its movement below surface. Soil erosion adversely hinders
the growth of plants, agricultural yields, quality of water, and recreation. It
is a key cause of degradation of soils as it occurs naturally on all lands (Bai
et al., 2010). Soil erosion causes
are basically water and wind, with each of these contributing to a significant
level of yearly soil loss. The erosion phenomenon is sometimes slow, where it
usually occurs immediately unnoticed, it can also occur at a rapid rate resulting
in a great loss of the upper part of the soil. Soil erosion on crop lands is
manifested in the reduction of the yield potential, surface water quality
reduction, and impaired drainage networks (Munodawafa, 2012). Among the
greatest adverse worldwide environmental concerns is soil erosion. This is
because it causes not only soil nutrient deprivation and degradation of land,
but it also leads to many notable off-site environmental problems such as
flooding, water siltation, and pollution (Al-Wadaey and Ziadat, 2014).
Soil erosion also
contributes to pollution of waterways by nutrients and by other agrochemicals
such as pesticides. This pollution leads to eutrophication of waterways and the
resulting impact on aquatic life as well as direct toxicity effects on
organisms (Owens et al., 2005).
Agrochemicals reach surface waterways as both dissolved and particulate forms,
and water erosion is often the source of the particulate material. Harmel et al. (2006) examined nitrogen (N) and
phosphorus (P) fractions in nutrient loads from watersheds in 15 states of the
United States of America and two provinces of Canada. Particulate nitrogen and
phosphorus loss contributed, on average, three times as much as dissolved forms
to loads, indicating the overriding effect of soil erosion and transport on
nitrogen and phosphorus loads. Phosphorus is a particular concern for
eutrophication. Phosphorus is strongly retained by solid phase and transported
as eroded solid particles and through transport of manure and human waste (Yuan
et al., 2018). Wind erosion causes
decrease in soil productivity. Wind erosion has additional linkages with
desertification–land degradation in arid, semi-arid and dry sub-humid areas
resulting from various factors, including climatic variations and human
activities and with direct human health issues associated with dust inhalation.
Human-induced wind erosion is a major cause of land degradation associated with
desertification (D’Odorico et al.,
2013).
1.4 ADVANTAGES AND
DISADVANTAGES OF SOIL EROSION
Natural soil erosion can
play beneficial role in the environment. In a paper written by Washington State
University Professor, I. C. Wheeting between 1940 and 1949, the benefits of
soil erosion were outlined to be that erosion help feed water sources with
essential nutrients which is consumed by aquatic life. It was also found that
erosion helps to cleanse the soil of useless materials that may be toxic to
plants. One of the main advantage of soil erosion is that it helps to fight
global warming by helping to move carbon to wetlands that store carbon for a
long time. Soil erosion also helps to form soil from weathered rocks. The
disadvantages of soil erosion is a result of loss of soil nutrients which are
required for plant growth, leading to soil infertility. Soil erosion also cause
pollution of natural water making water unsafe for drinking and toxic to
aquatic life and plants via the accumulation of toxic chemicals in water.
1.5 FACTORS THAT CONTRIBUTE TO SOIL EROSION
These factors contribute
to the possibility and rate of soil erosion occurrence and they include:
1.5.1 Climatic Factors
Gully erosion results from
the action of heavy rainfall on surface earth materials under reduced or
altered vegetative cover. The amount and the intensity of precipitation is the
main climatic factor influencing soil erosion. Other climatic factors like
strong winds and temperature range may also affect erosion.
1.5.2 Soil Nature
The composition, moisture
and compaction of soil are all major factors that determine the erosivity of
rainfall. Sediments containing more clay tend to be more resistant to erosion
than those with sand or silt, because the clay helps to bind soil particles
together (Mirsal, 2008). Soil containing high level of organic matter are often
more resistant to erosion, because organic matter coagulate soil to create more
stable soil structure (Blanco and Lal, 2010).
1.5.3 Topography
Topography of land
determines the velocity at which surface runoff will flow (Whisenant, 2008).
Longer, steeper slopes are more susceptible to very high rates of erosion
during heavy rainfalls than shorter, less steep slopes (Blanco and Lal, 2010).
Topography has a direct effect on the spatial pattern of water erosion. Erosion
increases in a linear relationship with increase in slope. This means that the
velocity of the runoff (and its erosive power) increases as slope increases.
1.5.4 Human Factors
According to Egede (2013)
soil has been subjected to intensive pressure from human uses that induce
degradation, soil loss and erosion; such human factors include overgrazing,
excessive farm activities, tillage, clearing of bushes, extractive industries,
road construction, bush burning, over-population, lumbering, residential
buildings, development of urban centres, industrialization, fumigation with
pesticides, mining (open cast and soil excavation) e.t.c. Human activities such
as construction works involving haphazard erection of buildings on steep
terrains, ineffective or uncompleted drainage projects encourage concentration
of runoff and gullies (Ibitoye and Adegboyega, 2012).
1.5.5 Vegetation
Crops and grasses support
the structure of soils, thereby decreasing the amount of soil erosion. Areas
with less naturally-occurring flora are more susceptible to soil erosion.
Vegetation protects the soil from raindrop impact and retards the formation of surface
seals. Plant roots increase macro-porosity and hence increase the infiltration
rate, thereby decreasing runoff (Gyssels et
al., 2005). Roots also increase the resistance of the soil to flow
detachment. Vegetation increases the friction to overland flow, decreasing the
velocity of flow and absorbing some of the erosion energy. Therefore, with
increasing vegetation density and as we move from cropland to grassland to
forest, we expect an increase in resistance by the soil to concentrated flow
erosion and a decrease in runoff discharge during a rainfall event (Torri and
Poesen, 2014). For non-cropped lands, they have the highest overall wind erosion
levels, and both grasslands and forests have significantly lower levels (Ravi et al., 2010).
1.6 AIM AND OBJECTIVES OF THE STUDY
The purpose of this study
is to evaluate the effect of soil erosion on microorganisms
1.6.1 Objectives of
the Study
1. To evaluate microorganisms from non-eroded soil sample
2. To evaluate microorganisms from eroded soil samples
3. To compare the microbial load of eroded soil samples and
non-eroded soil samples
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