Soil Degradation - Research Paper Example

Topic: Lecturer: Presentation: Introduction Soil degradation is the process through which soil loses value and productivity as a result of exposure to human and environmental influences. There are many forms of soil degradation. However, this paper will focus on soil erosion which is a major factor that affects soil productivity. Human activities are among the underlying causes of soil erosion. These activities have been highlighted. The impact of soil erosion has been discussed in detail. The paper also presents various methods that are being used to reduce or reverse its impact. The relevance of soil erosion to the sustainable use of soil has been discussed. Soil Erosion Soil erosion is a phenomenon that has been taking place for many years. Loose soil on the earth surface is moved by water and wind especially where the ground is bare. As the soil is formed, it is moved away to a different place if it is not covered or held tight by vegetation (Toy et al 2002). Intense human activity has caused soil in the recent past to be moved at a higher rate than its formation. Some activities such as overgrazing and inappropriate farming practices have increased the vulnerability of soil to erosion. Soil that is left bare is carried away by strong wind or rainfall and deposited in rivers and water masses (Cox and Ashley 2000). Rain splash is among the causes of soil erosion whereby very strong rain drops fall on bare soil detaching and moving it for a short distance. The effects of splash erosion are usually in-situ since the soil is only moved over a minimal distance. Moreover, the rain must fall with significant intensity for erosion to take place. The soil is re-distributed on the surface unless if the area is sloping. Rill erosion may occur when the soil is moved along channels down slope. When the intensity of rainfall is high, the channels may enlarge to form gullies. Gulley erosion is more pronounced in many parts of the world and is associated with mass movement of soil (Bathgate and Pannell 2002). Generally, when the rain falls on soil, a substantial amount of water is absorbed until the soil is saturated. It takes time for the water to infiltrate and therefore the more time the water remains on the soil surface the greater the possibility of absorption. Soil erosion is mainly attributed to overland flow, which is the water that does not infiltrate in to the soil. This occurs mostly when the rainfall is sudden and with high intensity giving little time for absorption. Excess runoff is moved down slope by gravity and as rills converge at the bottom of the slope, larger gullies are formed and the overall result is high intensity of erosion and huge soil deposits down slope (Boardman 2006). Wind is also a significant cause of soil erosion especially in semi-arid areas. It redistributes soil and may also move it over a long distance. Soil with detached individual particles through human and animal activities is susceptible to wind erosion. Soil may as well move down slope through tillage (Troeh, 2003). This is usually attributed to wrong methods of plowing, such as contour farming down slope. Apart from moving the soil, tillage creates weakness in soil layers making them susceptible to other forms of erosion. Soil erosion may take place in a gradual and unnoticeable manner eventually causing significant impacts on the soil. In most cases, people tend to control soil erosion once it has occurred rather than putting preventive measures in place to avoid its occurrence (Abel 2001). Impacts of Soil Erosion Soil erosion is a major environmental problem in the current day since it does not only affect the productivity of land in-situ but also affects the environment ex-situ where the soil is deposited. It has been a significant contributor of flash floods in areas down stream as soil layers accumulate in river channels thereby raising the riverbeds. The result has been mass displacement of populations and damage of crops (Vaclav 2000). On the other hand, soil erosion increases nutrient loading in water masses thereby causing eutrophication, which stimulates excess growth of aquatic plants. For example, the water hyacinth has become a menace in water masses such as Lake Victoria, which has adversely affected fishing and movement of cargo vessels. The land upstream is made infertile thereby increasing chances of starvation of populations. Moreover, soil erosion decreases the water holding capacity of soil leading to low soil moisture (Philip & Morgan 2005). In extreme cases of gulley erosion, roots of plants are left exposed while human life is endangered through open gullies on land. Subsequent rainfall may lead to massive flow of water within the gullies, which may lead to loss of property, livestock and human life. Soil erosion leads to siltation of water bodies such as dams and lakes and may affect water supply systems and hydro-electric power generation through clogging of pipes and decrease in water holding capacity of the reservoirs. Turbidity of water as a result of soil color increases the cost of domestic water treatment. On the other hand, the suspended soil particles adversely affect aquatic life especially fish that respire through gills. Disposal of pesticides in water masses also endanger human and aquatic life (Harmon & Doe 2001). Wind erosion on the other hand leads to the suspension of dust particles in the atmosphere obscuring visibility of drivers, which can cause serious accidents. The dust may settle on water masses causing pollution. Breathing dusty air can cause respiratory problems to humans. Coarse particles of soil travelling under the pressure of wind can damage crops and glass materials. The action of wind on the soil surface hinders its capacity to stock up nutrients and moisture leading to desiccation of soil, which adversely affects the environment. Generally, the effects of soil erosion are undesirable (Pannell and Vanclay 2011). Methods being used to Reduce or Reverse the Effect of Soil Erosion Farmers and conservationists have been putting efforts to control soil erosion after understanding its adverse impacts. Plowing across the slope is one of the significant methods that are being applied to curb the problem of soil erosion. This ensures that rill erosion is controlled as the rain water falling on the soil surface does not easily flow down slope. Overgrazing has been pointed out in this paper as one of the significant causes of erosion (Sanjari et al. 2009). Farmers being encouraged to keep few animals that do not exert a lot of pressure on the available land. However, there has been challenges in trying to campaign against overgrazing among the pastoralist communities since most of them believe their wealth is vested in the number of animals they possess (Seymour et al. 2010). Alexander et al. (2010) observe that planting of trees and allowing vegetative cover to spread over the land is necessary to ensure that land is not left susceptible to wind and splash erosion. As the rain falls on ground covered with vegetation, the water is allowed enough time to infiltrate in to the ground. Moreover, the vegetation holds the soil firmly making it difficult to be transported downstream by running water. Trees also act as wind breaks, playing a significant role in reducing the strength and speed of wind. Bench terraces are also constructed on farm to control soil erosion along slopes. These comprise a sequence of level strips in a row across the slope at perpendicular intervals reinforced by steep banks (Rouhipour et al. 2006). On-farm water harvesting is another method that is applied to allow rain water enough time to infiltrate in to the soil. This involves digging trenches at intervals along the slope such that any runoff is captured in the trench that holds it up to the time that the water is fully absorbed by the soil. Apart from infiltration of the water, nutrients are also arrested in the trench which ensures they remain within the locality. In other words, even though the nutrients are displaced, they are not moved far away down slope (Pannell and Vanclay 2011). Crop rotation is being encouraged in areas with high potential of soil erosion. Crops planted in rows reduce the risk of erosion but the situation is made better if they are rotated with sod crops such as wheat and hay that minimizes the risk of erosion by a greater percentage. In areas where erosion has caused greater damage over a long period of time, retaining walls are used to enhance recovery and prevent more erosion in future. Gabions are significant in areas where gulley erosion has adverse effects. They reduce the speed of overland flow and arrest any soil particles that would otherwise be transported downstream by water (Seymour et al. 2010). Relevance of Soil Erosion to the Sustainable use of Soil Soil is a significant and scarce natural resource that promotes human and animal life. Its sustainable use increases its utility and capacity to support life. Soil erosion has a significant impact in regard to sustainable use of soil. Its relevance is felt when other efforts of utilizing soil fail due to the loss of nutrients and the top soil that is needed for any farming activity to take place. Soil erosion control helps to maintain the characteristics of good soil that indicate its natural productivity (Harmon & Doe 2001). When the natural productivity of soil is managed in a proper way, the dependence on purchased artificial inputs is reduced while the value of land continues to increase. Many of the actions that involve spending in the efforts to maintain soil productivity such as adding commercial fertilizers can be avoided if soil erosion is controlled thereby reducing the cost of farming (Dilly and Pannell 2009). Sustainable use of soil involves utilization of soil to meet the present needs while maintaining its integrity for the purpose of future generations. Farmers have to ensure that the utility of the soil in future is not compromised. Soil erosion control is one of the activities that contribute to the concept of “best management practice”. The concept refers to the combination of soil management techniques along with agricultural management practices to establish the most efficient and cost-effective strategy to curb and prevent soil degradation (Vaclav 2000). Soil erosion is geared towards the reduction of physical and chemical pressure to soil through rainfall. It helps to protect the soil structure and organic matter within the soil layers. The manner in which soil particles are distributed within the soil layers is significant since it determines the water holding capacity and aeration of the soil. When soil fertility is maintained through erosion control, lightness of the soil structure is maintained thereby enhancing good drainage, water storage as well as aeration. The capacity of soil layers to hold a large amount of water and releasing it slowly is enhanced by high organic matter content. Soil erosion control prevents the organic matter from being washed away (Sanjari et al. 2009). Soil erosion control allows proper drainage of soil as well as warming, which is necessary for germination and growth of crops. It also allows the rain water to soak in to the soil leaving minimal runoff. Once the moisture has penetrated the soil layers, it is withheld for a long time allowing the soil to support germination long after the rains. Control of soil erosion allows micro-organisms to establish in the soil. These are useful in various biological activities that enhance soil productivity. Soil transported by runoff in to water bodies is not available for use. Rather, it becomes a problem to put the water in to usable state because of the silt (Seymour et al. 2010). Conclusion Loose soil on the earth surface is susceptible to soil erosion. Overgrazing, cultivating along the slope and clearing of vegetation are among the practices that increase vulnerability of soil to erosion. The various types of soil erosion include splash erosion and rill erosion, which at greater intensities may result to gulley erosion. Overland flow is the major cause of soil erosion. Wind contributes significantly to erosion of loose soil particles on the surface especially in the semi-arid areas. Soil deposited in water bodies may raise the river bed causing flash floods. Accumulation of nutrients in water masses and decreasing water holding capacity of soil results from soil erosion. Soil erosion can be prevented through various soil management practices including; plowing across the slope, planting cover crops, crop rotation, construction of bench terraces, on-farm water harvesting, and building of gabions. References Abel, D. 2001 Environmental Issues: Measuring, Analyzing, Evaluating, Prentice Hall, New Jersey. Alexander, J. Roberts, A.M. and Pannell, D.J. 2010. Victorian Catchment Management approaches to salinity: learning from the National Action Plan experience, Australasian Journal of Environmental Management 17(1), 45-52. Bathgate, A. and Pannell, D.J. 2002 Economics of deep-rooted perennials in southern Australia. Agricultural Water Management 53(1), 117-132. Boardman, J. 2006 Soil erosion science: Reflections on the limitations of current approaches. Catena 68(3), 73-86. Cox, J.W. and Ashley, R., 2000 Water quality of gully drainage from texture-contrast soils in the Adelaide Hills in low rainfall years. Australian Journal of Soil Research, 38(2), 959-972. Dilly, O. and Pannell, D. 2009 Editorial: Sustainability impact assessment and land-use policies for sensitive regions, Environmental Science and Policy 12(8), 1075-1076. Harmon, R. S. & Doe W. W. 2001 Landscape erosion and evolution modeling, Springer, New York. Pannell, D.J. and Vanclay, F.M. 2011 Changing Land Management: Adoption of New Practices by Rural Landholders, CSIRO Publishing, Canberra. Philip, R. & Morgan C. 2005 Soil erosion and conservation, John Wiley and Sons, New Jersey. Rouhipour, H., Ghadiri, H., and Rose, C.W. 2006 Investigation of the interaction between flow-driven and rainfall-driven erosion processes. Australian J Soil Research, 44, 503-514. Sanjari, G., Yu, B., Ghadiri, H., Ciesiolka, C.A.A., and Rose, C.W. 2009 Effects of time-controlled grazing on runoff and sediment loss. Australian Journal of Soil Research. 47, 796-808. Seymour, E., Curtis, A., Pannell, D., Allan, C. and Roberts, A. 2010 Understanding the role of assigned values in natural resource management. Australasian Journal of Environmental Management 17, 142-153. Toy, T. J. Foster, G. R. Renard, K. G. 2002 Soil erosion: processes, predicition, measurement, and control, John Wiley and Sons, New Jersey. Troeh, F. 2003 Soil and Water Conservation for Productivity and Environmental Protection, Prentice Hall, New Jersey. Vaclav, S. 2000 Feeding the world: a challenge for the 21st century, MIT Press, Cambridge. Read More