Soil erosion, which is a form of soil degradation, may be relatively unnoticed due to the fact that it can be a slow process, but it can cause some serious damage and loss to our water quality, crop production and drainage networks.
Variables that influence erosion:
Rainfall and wind velocity: Rainfall is one of the biggest factors when looking at erosion. It causes soil erosion by means of splash. This means that it is caused by the impact of the raindrop directly onto the soil. When rain falls gently, the soil will absorb the rain and only some of the rain will slowly run off the slope, but when it rains hard and in big, strong volumes, there is no time for water to soak through the soil and it runs off causing erosion. The intensity of the erosion is caused by how much rain fell, duration of rain and the frequency of rainfall.
Topography: When the soil has a steep slope, it will accelerate the erosion process as the velocity of flowing water will be increased. Along with this comes the physical and chemical properties of soil – The soil’s structure, texture, organic matter, salts present, and the nature of the day will play a role in how quick it erodes. Some soil has more organic manure and will therefore have an improved granular structure and water holding capacity – thus this type of soil will not erode so fast. Other types of soil again are more fine-textured and consists of alkaline. They are more crodible.
Lastly, we can look at the vegetation or ground cover – it goes without saying that the more the ground cover, the more the erosion process gets retarded. An area covered with grass or forest roundabouts will be more effective in providing coverage than a crop plantation. Take the splash erosion mentioned at the top, as example. The more vegetation there is to cover the soil, the harder it will be for the raindrop to directly land on and damage the soil underneath the plantation. Instead it will land on the vegetation and make its way to the soil. From here it will flow into the soil, where it will create a bigger storage capacity.
Prime causes of accelerated erosion:
Again, physical factors such as rainfall, surface runoff, wind erosion and floods can be considered as some of the prime causes of soil erosion. Mostly caused by wind or water, these physical forces change the soil’s composition and structure as it wears away the top layer of the soil and removes the organic matter. It leads to a decline in soil fertility.
Biological factors such as human and plant activity also tends to reduce the quality of soil. When farmers practice poor farming activity, they deplete the soil nutrients and therefore diminish soil fertility. When there is a bacterial or fungi overgrowth in the soil, it can also impact the microbial activity of the soil and reduce crop yield and soil productivity capacity. Soil infertility will result in less vegetation growth which will in turn result in much quicker erosion when accompanied by strong rainfall.
Salt build-up and leaching of nutrients corrupt the quality of soil as it creates changes in the soil chemical ingredients. This causes soil to lose nutrients and productivity capacity – it hardens iron and aluminium rich clay soils into hardpans, preventing water to flow into soil. Erosion will thus take place easier here. This is all results of chemical factors in soil which. Alkalinity and acidity also plays a role here and can be categorized under chemical components of soil degradation.
Soil degradation can also be caused by deforestation. Trees and crop cover gets removed and soil is exposed to rain and slash and logging, which all contributes to soil erosion. Vegetation cover helps binding soil together and contributes to soil formation, therefore when removing it, soil capabilities such as aeration, water holding capacity and biological activity gets affected negatively.
The excessive use of fertilisers kills organisms that assists in binding soil together. Soil that is not bonded, will erode much faster that soil that tightly bonds as also mentioned above. Some forms of fertiliser’s chemicals are also responsible for denaturing essential soil minerals, meaning there is a nutrient loss in the soil.
Agricultural practices are one of the biggest contributors of soil quality decline. Tillage on agricultural lands are one of the main factors in soil erosion as it breaks the soil up in smaller, finer pieces and thereby increases erosion rates. Improper cultivation activities such as farming on steep slopes, row-cropping, mono-cropping and surface irrigation wear away the natural composition of soil, prevent it from regenerating and definitely contributes soil erosion and degradation.
Urbanization also has major implications on soil degradation. It denudates the vegetation cover, alters draining patterns and compacts soil during construction. Soil gets covered in a layer of concrete that amplifies the amount of surface runoff. This results in more erosion of the top soil. Overgrazing also increases the rates of soil erosion as it destroys the surface crop cover and breaks down soil particles.
Effects that wind and water erosion could have on soil
The effect that water has on soil erosion is much more than the obvious removal of the valuable topsoil. When water erosion takes place, seeds and plants can be completely removed from the soil. Organic matter and pesticides that is necessary for successful growth can also be removed and carried off site by water erosion. Soil structure are weakened by the breakdown of organic matter and removal of layers of soil, and texture are changed. The change in texture can affect water-holding capacity, making it more susceptible to extreme conditions such as drought. Sediments that are carries with the water and reaches streams or watercourses and obstruct stream and drainage channels and accelerate bank erosion. Soil can be influenced by many types of water erosion: Sheet erosion is caused by the movement of soil from raindrop splash and runoff water. There will be an accumulation of soil and debris at the lower end of the field where erosion took place. Rill erosion is caused by water runoff and forms small defined channels in the soil. Gully erosion is only the advance stage of rill erosion and develop where the rill erosion has not been managed. Bank erosions is the progressive undercutting, scouring and slumping of natural stream and drainage channel banks. Transformed land due to lots of water is unable to soak up water, making flooding a more frequent effect. Soil degradation takes away the soil’s natural capability of holding water and thus contributing to more cases of flooding. A lot of soil eroded from land are discharged into waterways and streams – along with all the chemical fertilisers and pesticides that was used. This can cause pollution as well as clogging of waterways.
Wind erosion takes place where there are sandy and organic soils. Wind erosion can cause major losses of soil and property. Depending on soil particle size and how strong the wind is, soil particles can move in three ways: suspension, saltation and surface creep. Wind erosion damages crops through sandblasting of seedlings, transplants, burial of plants and exposure of seeds. Crops are basically then ruined, and reseeding will be necessary. In some areas, wind erosion is a constant occurrence where soil drifting takes place and depletes fertility in the soil leading to poor crop growth. The constant drifting also causes textural change, loss of fine sand and organic particles which will lower the moisture-holding capacity of the soil. This increases the erodibility of the soil.
Having wind-blown soils removed from drainage channels, fence rows, buildings and roads can be a costly process. Off-site impacts can be caused by soil nutrients and surface applied chemicals which gets carried along with the soil particles during wind erosion. It can affect human health and create public safety hazards. The rate and magnitude of soil erosion by wind is controlled by the following factors: Soil erodibility, soil surface roughness, climate, unsheltered distance and vegetation cover.
Soil protection techniques:
In order to reduce soil degradation and erosion, a few drastic steps will need to be taken. Reduce deforestation – Although it cannot be completely avoided, it can at least be cut down a bit. People need to be educated (in schools and in work environments) regarding sustainable forest management and reforestation efforts. Humanity needs to respect forest cover and learn to be more considerate of the world – especially when it comes to our natural environment. If deforestation can be reduced, soils will be able to naturally regenerate itself. Governments, environmental stakeholders and international organisations needs to make sure that there are appropriate measures of making zero net deforestation a reality. This way soil can be protected.
Lost soil minerals and organic matter needs to be restored. This can be done by a process called land reclamation, which consists of activities such as addition of plant residues to degraded soils and improving range management. A very simple way of land reclamation is also by planting trees and crops and flowers over the affected soils. The plants will act as protective covers as they will help making soil stronger and stabilise land surface.
Preventing salinization are much cheaper than the reclamation projects in salinized areas. Reducing irrigation, planting salt tolerant crops and improving irrigation efficiency will definitely be rewarding, because the inputs and labour-demanding aspects associated with reclamation and restoration projects are zero.
Lastly, conservation tillage. Proper tillage mechanisms are one of the most sustainable ways of avoiding soil degradation. Very little changes are made to soil’s natural condition and this at the same time improves the soil productivity. A good example of this can be when leaving the previous year’s crop residue on the land’s surface to shield soil from erosion. Also, avoid poor tillage methods like deep ploughing.
Soil erosion is not something to avoid as soil are the basis of all terrestrial life. The erosion is a clear effect of poor agricultural management and improper use. It needs to be seen as a serious environmental problem. Avoiding it is crucial to our well-being.