To Strip Areas So Bare That Winds Can Blow Away the Soil
Soil erosion
Soil erosion occurs when soil is removed through the action of wind and h2o at a greater charge per unit than it is formed
Soil
The soil roofing the surface of the earth has taken millions of years to form and we must learn to respect it. Soil is formed at a charge per unit of only ane cm every 100 to 400 years and it takes 3 000 to 12 000 years to build enough soil to form productive country. This means that soil is a nonrenewable resource and one time destroyed it is gone forever.
If nosotros disregard this, a time will come when there would non be enough soil left to sustain life on earth, because the soil is a necessary growth medium for plants, a home for sure insects and animals, also equally a medium from which nosotros get minerals, such as gold. It is important therefore to treat soil, especially topsoil, as a living entity.
What is soil erosion?
• When a raindrop hits soil that is not protected by a cover of vegetation and where there are no roots to demark the soil, information technology has the bear upon of a bullet.
• Soil particles are loosened, washed downwardly the slope of the land and either end upwardly in the valley or are washed away out to body of water by streams and rivers.
• Erosion removes the topsoil first. Once this nutrient-rich layer is gone, few plants will grow in the soil again.
• Without soil and plants the land becomes desertlike and unable to back up life.
Causes of soil erosion
Erosion occurs when farming practices are not uniform with the fact that soil can exist done abroad or blown away. These practices are:
• Overstocking and overgrazing
• Inappropriate farming techniques such every bit deep ploughing land 2 or 3 times a year to produce almanac crops
• Lack of crop rotation
• Planting crops downwards the contour instead of along it.
Water erosion
Water erosion causes ii sets of issues:
• an on-site loss of agricultural potential
• an off-site effect of downstream movement of sediment, causing flooding and the silting upward of reservoirs.
Canvas erosion• Soil erosion is characterised by the downslope removal of soil particles within a thin canvas of water. • Sheet erosion occurs when the entire surface of a field is gradually eroded in a more or less uniform fashion. • It is a gradual process and it is non immediately obvious that soil is beingness lost. |  |
Gully erosion (dongas)Dongas usually occur near the bottom of slopes and are acquired past the removal of soil and soft rock every bit a result of full-bodied runoff that forms a deep channel or gully. On steep country, there is oftentimes the danger of gullies forming. Water running downhill cuts a aqueduct deep into the soil and where there is a sudden fall, a gully caput forms at the lower end of the channel and gradually works its style dorsum uphill. As information technology does so, it deepens and widens the scar that the gully makes in the hillside. Gully erosion is related to streambank erosion, in which fast-flowing rivers and streams increasingly cut down their own banks. |  |
Rill erosion (aqueduct erosion)Channel erosion tin can occur on steep land or on land that slopes more gently. Because there are always irregularities in a field, h2o finds hollows in which to settle and low-lying channels through which to run. Equally the soil from these channels is washed away, channels or miniature dongas are formed in the field. |  |
Wind erosion
Wind erosion occurs when the land surface is left blank in regions that are barren enough, as a effect of low rainfall, to allow the soil to dry out, and flat enough to permit the air current to carry the soil away over several consecutive days. Land may become susceptible to wind erosion through grazing animals, which remove the protective establish cover, and whose hooves break up the soil, specially circular watering points. Arable land that has been left bare is as well a major problem.
Factors determining soil erosion
There are various factors determining soil erodibility of which the following are the most important:
Slope
The steeper the gradient, the greater the erosion, every bit a outcome of the increased velocity (swiftness) of h2o-menstruum. The length of the slope is very important, considering the greater the size of the sloping expanse, the greater the concentration of the flooding water.
| Soil texture Soil texture is the size distribution of soil particles. The size of particles never changes. A sandy soil, therefore, remains sandy and a clayey soil remains clayey. The three main particles are sand, silt and clay. The more sandy a soil the easier it will erode. | To examination the soil blazon: Roll the soil into a sausage between your hands and try to class a circle. | Clayey soil | Sandy-loam soil |
Sandy soil | |||
Soil construction
The term soil structure means the grouping or arrangement of soil particles. Overcultivation and compaction cause the soil to lose its structure and cohesion (ability to stick together) and it erodes more hands.
Terrain unit
The crest (superlative of slope) is ordinarily well drained as soil wet moves downhill, leaving air in the pore spaces almost of the time. Over time, the fine (clay) particles are carried downslope leaving the soil sandy. Institute roots can penetrate easily to deep levels and withdraw enough soil water from there. These soils have a lower erosion potential and are commonly more stable.
In the midslope soil moisture moving from the crest starts to dam upwardly as a effect of the clay-rich soil only downhill. The soils are moderately well drained with a college erosion potential.
In the footslope the soil has been waterlogged (saturated with water) as a result of the long-term aggregating of clay which does not allow water to infiltrate. Plants that grow on these soils are limited to those that tin can accommodate their root systems to grow laterally to a higher place the hard clayey layer. These imperfectly tuckered soils take a high erosion potential.
 | |
| Crest | |
| Midslope | |
| Footslope | |
Organic material
Organic material is the "glue" that binds the soil particles together and plays an important part in preventing soil erosion. Organic affair is the main source of free energy for soil organisms, both found and animate being. It also influences the infiltration capacity of the soil, therefore reducing runoff.
Vegetation cover
The loss of protective vegetation through overgrazing, ploughing and burn down makes soil vulnerable to being swept away past wind and h2o. Plants provide protective cover on the land and prevent soil erosion for the post-obit reasons:
• Plants tedious down water equally it flows over the country and this allows much of the rain to soak into the ground.
• Plant roots hold the soil in position and prevent it from being diddled or washed away.
• Plants pause the bear on of a raindrop before it hits the soil, reducing the soil's ability to erode.
• Plants in wetlands and on the banks of rivers are of import equally they ho-hum down the flow of the water and their roots demark the soil, preventing erosion.
State utilize
Grass is the best natural soil protector against soil erosion because of its relatively dense cover. Small grains, such equally wheat, offer considerable obstruction to surface wash. Row crops such as maize and potatoes offer little encompass during the early on growth stages and thereby encourage erosion. Fallowed areas, where no crop is grown and all the residual has been incorporated into the soil, are most subject to erosion.
Preventing soil erosion
Some of the post-obit measures tin can be implemented to prevent soil erosion:
• The use of contour ploughing and windbreaks
• Go out unploughed grass strips between ploughed lands (strip cropping)
• Brand sure that there are always plants growing on the soil, and that the soil is rich in humus
• Avert overgrazing
• Allow indigenous plants to grow along riverbanks
• Conserve wetlands
• Cultivate land, using a crop rotation arrangement
• Minimum or no tillage
• Encourage water infiltration and reduce h2o runoff.
| 1999 Compiled past Advisers Communication, National Department of Agriculture Printed and published by National Department of Agriculture |  |
Source: https://www.nda.agric.za/docs/erosion/erosion.htm
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