Thus, the loss of the topsoil can have considerable impact on yield, where nutrient availability, root growth environment, and soil water availability are essential for plant development. In soils with unfavorable subsoil conditions, erosion can have a large effect on productivity, if the plow layer soil fertility is not restored. Plant residue management is another way of controlling soil erosion by intercepting raindrops, thereby reducing surface runoff and protecting soil surface particle detachment by raindrop impact.
Crop residue can provide an excellent soil cover after harvest and enhance snow harvesting during the off season, improve soil water intake by preventing soil surface sealing due to raindrop impact, and consequently, reduce surface runoff. Equally important in minimizing soil erosion is the adoption of a cropping system along with conservation tillage practices such as no-till, strip-till, and ridge-till.
The degree of effectiveness of different tillage practices depends on the degree of soil manipulation, which effects the residue distribution on the soil surface. Table 1 shows combinations of different cropping systems and the relative scale of erosion hazard associated with each system. You are here Home.
Soil erosion: An agricultural production challenge Encyclopedia Article. Types of Erosion Sheet erosion water is almost invisible. Lighter colored soils are a sign that over the years erosion has taken its toll. Wind erosion is highly visible. Although it is a problem, water erosion is generally much more severe. Rill erosion occurs during heavy rains, when small rills form over an entire hillside, making farming difficult. Gully erosion makes gullies, some of them huge, impossible to cross with farm machinery.
Ephemeral erosion occurs in natural depressions. It differs from gully erosion in that the area can be crossed by farm equipment. Table 1.
Figure 6. Bank erosion involves the undercutting and scouring of natural stream and drainage channel banks. Poorly constructed tile outlets also contribute to bank erosion. Some do not function properly because they have no rigid outlet pipe, have an inadequate splash pad or no splash pad at all, or have outlet pipes that have been damaged by erosion, machinery or bank cave-ins. The direct damages from bank erosion include loss of productive farmland, undermining of structures such as bridges, increased need to clean out and maintain drainage channels and washing out of lanes, roads and fence rows.
The implications of soil erosion by water extend beyond the removal of valuable topsoil. Crop emergence, growth and yield are directly affected by the loss of natural nutrients and applied fertilizers. Seeds and plants can be disturbed or completely removed by the erosion. Organic matter from the soil, residues and any applied manure, is relatively lightweight and can be readily transported off the field, particularly during spring thaw conditions.
Pesticides may also be carried off the site with the eroded soil. Soil quality, structure, stability and texture can be affected by the loss of soil. The breakdown of aggregates and the removal of smaller particles or entire layers of soil or organic matter can weaken the structure and even change the texture.
Textural changes can in turn affect the water-holding capacity of the soil, making it more susceptible to extreme conditions such as drought. The off-site impacts of soil erosion by water are not always as apparent as the on-site effects. Eroded soil, deposited down slope, inhibits or delays the emergence of seeds, buries small seedlings and necessitates replanting in the affected areas.
Also, sediment can accumulate on down-slope properties and contribute to road damage. Sediment that reaches streams or watercourses can accelerate bank erosion, obstruct stream and drainage channels, fill in reservoirs, damage fish habitat and degrade downstream water quality.
Pesticides and fertilizers, frequently transported along with the eroding soil, contaminate or pollute downstream water sources, wetlands and lakes. Because of the potential seriousness of some of the off-site impacts, the control of "non-point" pollution from agricultural land is an important consideration. Wind erosion occurs in susceptible areas of Ontario but represents a small percentage of land — mainly sandy and organic or muck soils.
Under the right conditions it can cause major losses of soil and property Figure 7. Figure 7. Wind erosion can be severe on long, unsheltered, smooth soil surfaces.
Soil particles move in three ways, depending on soil particle size and wind strength — suspension, saltation and surface creep. The rate and magnitude of soil erosion by wind is controlled by the following factors:.
Very fine soil particles are carried high into the air by the wind and transported great distances suspension. Fine-to-medium size soil particles are lifted a short distance into the air and drop back to the soil surface, damaging crops and dislodging more soil saltation. Larger-sized soil particles that are too large to be lifted off the ground are dislodged by the wind and roll along the soil surface surface creep.
The abrasion that results from windblown particles breaks down stable surface aggregates and further increases the soil erodibility. Soil surfaces that are not rough offer little resistance to the wind. However, ridges left from tillage can dry out more quickly in a wind event, resulting in more loose, dry soil available to blow.
Over time, soil surfaces become filled in, and the roughness is broken down by abrasion. This results in a smoother surface susceptible to the wind. Excess tillage can contribute to soil structure breakdown and increased erosion. The speed and duration of the wind have a direct relationship to the extent of soil erosion. Soil moisture levels are very low at the surface of excessively drained soils or during periods of drought, thus releasing the particles for transport by wind.
This effect also occurs in freeze-drying of the soil surface during winter months. Accumulation of soil on the leeward side of barriers such as fence rows, trees or buildings, or snow cover that has a brown colour during winter are indicators of wind erosion. A lack of windbreaks trees, shrubs, crop residue, etc.
Knolls and hilltops are usually exposed and suffer the most. The lack of permanent vegetative cover in certain locations results in extensive wind erosion. Loose, dry, bare soil is the most susceptible; however, crops that produce low levels of residue e.
In severe cases, even crops that produce a lot of residue may not protect the soil. The most effective protective vegetative cover consists of a cover crop with an adequate network of living windbreaks in combination with good tillage, residue management and crop selection.
Wind erosion damages crops through sandblasting of young seedlings or transplants, burial of plants or seed, and exposure of seed. Crops are ruined, resulting in costly delays and making reseeding necessary. Plants damaged by sandblasting are vulnerable to the entry of disease with a resulting decrease in yield, loss of quality and market value. Also, wind erosion can create adverse operating conditions, preventing timely field activities.
Soil drifting is a fertility-depleting process that can lead to poor crop growth and yield reductions in areas of fields where wind erosion is a recurring problem. Continual drifting of an area gradually causes a textural change in the soil. Loss of fine sand, silt, clay and organic particles from sandy soils serves to lower the moisture-holding capacity of the soil.
This increases the erodibility of the soil and compounds the problem. The removal of wind-blown soils from fence rows, constructed drainage channels and roads, and from around buildings is a costly process. Also, soil nutrients and surface-applied chemicals can be carried along with the soil particles, contributing to off-site impacts.
In addition, blowing dust can affect human health and create public safety hazards. Tillage erosion is the redistribution of soil through the action of tillage and gravity Figure 8. It results in the progressive down-slope movement of soil, causing severe soil loss on upper-slope positions and accumulation in lower-slope positions. The three main particles are sand, silt and clay. The more sandy a soil the easier it will erode. To test the soil type: Roll the soil into a sausage between your hands and try to form a circle.
Clayey soil. Sandy-loam soil.
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