BACKGROUND OF THE STUDY
Erosion is defined as the
washing away of the top soil due to excessive rainfall resulting to
surface run off or as a result of denudation and weathering processes.
Agriculture as defined by Robert (2015) is the growing of crops and
rearing of animals for man’s benefit. In view of the above definitions,
it could be seen that agriculture depends on land for its sustenance.
Carey and Oettli (2006) have observed that man through his anthropogenic
activities has degraded the natural land resources which have in turn
created erosional problems.
In recent times, studies have shown that
erosion has become a worldwide environmental issue that has called for
urgent attention and global redress (Edward, 2016). This shows that
erosion has become a menace in the modern day society especially in the
tropical regions. It has been observed that erosion has a direct effect
on arable crop production and agricultural productivity (Carey and
Soil carried off in rain or irrigation
water can lead to sedimentation of rivers, lakes and coastal areas
(Edward, 2016). The problem is exacerbated if there is no vegetation
left along the banks of rivers and other watercourses to hold the soil.
This soil carried away by erosional processes is mostly needed for
arable agriculture. Sedimentation mainly caused by erosion has caused
serious damage to freshwater and marine habitats, as well as the local
communities that depend on these habitats. For example, people living in
the river banks of River Niger often experience flooding of
agricultural produce which results to pre-mature harvest during the
rainy season. This trend is attributed to changes in the courses of
waterways resulting from farming-related erosion and the silt deposition
this causes (Gelder and Dros, 2006). They added that it's not just the
eroded soil that is damaging: pesticides and fertilizers carried in rainwater and irrigation runoff can pollute waterways and harm wildlife.
Land degradation stretches to about 30 %
of the total global land area (Carey and Oettli, 2006). The problem
persists, with a reported loss rate of about 10 million hectares per
year. In reality, the situation may be much more worrying. Over the last
5 decades, increases in agricultural productivity have made it possible
to produce more crops on the same amount of land. But the problem is
that because agricultural land is often degraded and almost useless,
producers keep on moving to more productive land. Globally, the land
used and abandoned in the last 50 years may be equal to the amount of
land used today (Carey and Oettli, 2006).
Vegetation strongly affects soil
characteristics including soil volume; chemistry and texture which
feedback affects various vegetation characteristics including
productivity and structure (Ndakara and Efe, 2010). Economic concerns
will also emerge with rapid urban growth examples include accidental or
intentionally started fires will increase, costing additional dollars
and resources to suppress the flames that threatens homes, business and
buildings. Threats to nature having information in cities impact to
these endangered species and protected areas enables planners to shape
the growth of cities before it is too late (Ndakara and Abotutu, 2010).
However, the lack of funding especially in developing countries may
prevent the implementation of smart-growing plans and expanded public
transit system, paving the way for more vehicles and driven contributing
more green house gases to the atmosphere a major cause of climate
change (Efe and Ndakara, 2010).
Recent studies have shown that erosion
caused by deforestation can also lead to increased flooding of farms and
damage of agricultural produce (Nkonya, 2016). In plantations, for
example, flooding occurs partly because of deforestation (soil is no
longer there to absorb the water) and partly because of poorly
constructed plantation drainage systems (Nkonya, 2016). This study is
carried out to investigate the effect of soil erosion on arable
agricultural production with special emphasis on the case of Asaba and
1.2 STATEMENT OF RESEARCH PROBLEM
The major problems which this study seeks to address includes:
Loss of cropland:
Erosion often causes loss of cropland and low agricultural productivity
in most rural farms. Since humans worldwide obtain more than 99.7% of
their food (calories) from the land and less than 0.3% from the oceans
and aquatic ecosystems, preserving cropland and maintaining soil
fertility should be of the highest importance to human welfare (David
and Michael, 2013). This loss of cropland to the effects of soil erosion
often results in the creation of new cropland out of forestland and
pastureland and the need to enrich these new croplands with inputs of
nitrogen and phosphate fertilizers (Pimentel, 2013).
Soil erosion is one of the most serious
threats facing world food production. Each year about 10 million ha of
cropland are lost due to soil erosion, thus reducing the cropland
available for world food production (David and Michael, 2013). The loss
of cropland is a serious problem because the World Health Organization
and the Food and Agricultural Organization report that two-thirds of the
world population is malnourished. Overall, soil is being lost from
agricultural areas 10 to 40 times faster than the rate of soil formation
imperiling humanity’s food security (David and Michael, 2013).
Loss of farmlands:
Erosion occurs after torrential down pour of rainfall with very high
intensity leading to destruction of farmlands which affects agricultural
productivity. It is mostly caused by the clearing away of the natural
vegetation for agricultural activities (Nkonya, 2016). When natural
vegetation is cleared and when farmland is ploughed, the exposed topsoil
is often blown away by wind or washed away by rain or perhaps erosion
thereby causing poor agricultural crop yield (FAO, 2006; Edward,
2016). This leads to reduced soil fertility and degraded land. Other
major crops mostly affected by soil erosion include coffee, cassava, cotton, corn, palm oil, rice, sorghum, tea, tobacco, and wheat (Carey and Oettli, 2006).
Loss of natural ecosystem:
Another serious problem affecting the sustainability of the rainforest
vegetation and the natural ecosystem is soil erosion. Soil erosion
remains the world’s biggest environmental problems affecting the
rainforest vegetation as well as threatening the sustainability of
systems, and thereby the security of their major components (Ndakara and
Soil infertility: The
loss of soil from land surfaces by erosion is widespread and reduces the
productivity of all natural ecosystems as well as agricultural, forest,
and pasture ecosystems (Troeh, et al., 2004; Lal, et al., 2010; Pimentel, et al,
2015). Concurrently with the growing human population, soil erosion,
water availability, climate change due to fossil fuel consumption,
eutrophication of inland and coastal marine bodies of water, and loss of
biodiversity rank as the prime environmental problems throughout the
Loss of soil nutrient:
Currently nearly 66% of the world population is malnourished (WHO, 2013;
Pimentel and Satkiewicz, 2013), the largest number of malnourished
people ever (malnutrition: faulty nutrition due to inadequate or
unbalanced intake of nutrients or their impaired assimilation or
utilization) (Gove, 2011). With the world population now over seven
billion and expected to reach 9.3 billion by 2050, more food will be
needed (UN, 2011). Consider at present that more than 99.7% of human
food (calories) comes from the land (FOA, 2004), while less than 0.3%
comes from the marine and aquatic ecosystems. Maintaining and augmenting
the world food-supply basically depends on the productivity and quality
of all agricultural soils.
Damage to arable agricultural land:
Human induced soil erosion and associated damage to all agricultural
land over many years have resulted in the loss of valuable agricultural
land due to abandonment and reduced productivity of the remaining land
which is partly made up for by the addition of nitrogen and phosphate
fertilizers (Pimentel, et al., 2015; Young, 2008; Lal, 2006;
Pimentel, 2006). In addition, soil erosion reduces the valuable
diversity of plants, animals, and soil microorganisms.
Soil erosion is a disastrous
environmental problem throughout the world. Erosion is a slow insidious
problem that is continuous. Indeed, 1 mm of soil, easily lost in one
rain or wind storm, is so minute that its loss goes unnoticed by the
farmer and others. Yet this loss of soil over a hectare of cropland
amounts to about 15 t/ha. Replenishing this amount of soil under
agricultural conditions requires approximately 20 years, meanwhile the
lost soil is not available to support crops. Along with the loss of soil
is the loss of water, nutrients, soil organic matter, and soil biota.
The soil system is severely harmed when soil erosion is allowed to
Food insecurity: Future
food security is threatened where cropland degradation is allowed to
occur because of significantly reduced crop productivity. Shortages of
cropland are already having negative impacts on world food production
(Pimentel, et al., 2009). For example, the Food and
Agricultural Organization (FAO) of the United Nations reports that the
per capita grain production has been declining for more than two
decades, based on the availability of grains. Although grain yields per
hectare in both developed and developing nations are still increasing,
these increases are slowing.
Worldwide, soil erosion continues
unabated while the human population continues to increase rapidly and
66% of the world population is now malnourished (WHO, 2013). If soil
conservation is ignored and population control is ignored, more
malnourished people and more deaths will occur. It is against this
background that this study is therefore carried out to address the
aforementioned problems and proffer lasting solution and management
1.3 AIM AND OBECTIVES
The aim of this study is to
examine the effect of soil erosion on arable agricultural production.
Therefore, the specific objectives are to:
- identify the prevailing types of soil erosion;
- ascertain the causes of soil erosion in the study area;
- examine the practice of arable agricultural production;
- examine the soil characteristics in the arable farm areas and control areas;
- Suggest possible ecological approaches to manage the degraded farm-land areas.
1.4 RESEARCH HYPOTHESES
In this study, the following hypotheses was drawn to act as guide to the researcher.
- There is no significant difference in soil bulk density degraded and control sites soils at the 0.05 level of confidence.
- There is no significance difference in soil exchangeable potassium
between degraded and control sites at the 0.05 level of confidence.
1.5 SIGNIFICANCE OF THE STUDY
will cover the whole of Asaba and will critically evaluate the effect of
soil erosion on arable agricultural production in the study area. It
would offer suggestion (s) on the causes and effects of soil erosion.
Therefore, the study will help
to unfold the deteriorating effect of soil erosion and major farmland
areas in the study area mostly affected by soil erosion. The study will
also take a deeper view on the causes of soil erosion in Asaba, and also
to look at or proffer solution (s) to combat the enormous problems of
soil erosion on the urban landscapes as well as rural landscapes in the
1.6 SCOPE AND LIMITATION OF THE STUDY
The scope of
this study was strictly based on effect of soil erosion on arable
agricultural production in Asaba; and to offer suggestion on the causes
and effects of soil erosion arable farmlands as well as both the urban
and rural landscape.
The scope of this study will
cover farmlands and agricultural sites. The scope of the study was
initially deigned to cover all the quarters in Asaba which includes;
Ibusa, Inebisi, Ezenei, Okpanam, Okwe, Okoh, Ogbe-Ogonogo, and Anwai.
However, because of time and financial constraints, the scope was scaled
down. In this regard only selected major quarters were covered in this
study. The time frame was inadequate to properly carry out extensive
notwithstanding, the data gathered from this study and research finding
will be of invaluable assistance of the study of urban sprawl and urban
1.7 STUDY AREA
1.7.1 Location, Size and Boundary
Geographically, Asaba is located in the
North-West region of Delta State and falls under the Delta-North
Senatorial District. Asaba is located in the South-South Geopolitical
zone of Nigeria and in the Niger Delta Region. Asaba covers a total land
area of approximately 189km2 (73mile2) (Opone, 2005). It lies between the geographical coordinate of latitudes 060 051N to 060 251N and longitudes 060 051E to 060 301E of the Greenwich meridian.
Asaba shares boundary in the North by
Oshimili North Local Government Area, in the West by Aniocha South Local
Government Area, in the East by Onitsha South Local Government Area of
Anambra State and in the South by Ndokwa East Local Government Area of
Delta State. Asaba shares boundary linguistically in the West with
Aniocha language speakers, in the East with the Igbo Speaking group, in
the North with the Oshimili Speakers and in the South with the Ukwani
speakers. The dialect which belongs to the Igbo group is among one of
the major ethnic groups in Delta State and Nigeria at large.
Asaba is one of the biggest cities in
Delta State which developed into a metropolis. It is found in Oshimili
South Local Government Area of Delta State. Neighborhoods in Asaba
include; Okwe Community, Onitsha, Igodo, Ogwashi-Uku, Anwai, Illah,
Onicha-Olona, Onicha-Ugbo, Ubulu-Uku, and a host of others.
Asaba as an urban area has experienced a
rapid increase in size over the years, due to the presence of various
administrative offices and governmental functions it performs both as
the administrative headquarters of Oshimili Local Government Area of
Delta State where the Council Secretariat is situated along
Asaba-Onitsha expressway; and as the capital of Delta State. This is
also as a result of the presence of the international airport in the
area. This attracts people from surrounding area, to itself, because of
its employment opportunities thus resulting in over-crowding, increased
demand for land basically meant for agricultural purpose leading to
shortage of land for farm practices.
The implication of these increase in
size, is that it has led to population explosion in urban areas of Asaba
which has in turn resulted in the development of its surrounding rural
areas both in expansion and infrastructural development due to urban
expansion. This has in turn had an adverse effect on the inhabitants of
Asaba and its environs especially on their agricultural system.