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 Oetti, 2006).
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 it’s environ.
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).