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Erosion is one of the most damaging phenomenon of nature. Whole civilizations have been wiped away by erosion, and their soil has been washed into river beds. Our own culture is also at risk; we build entire cities on sinkholes, and know that the sinkholes are there. In some places as much as 50 tons an acre a year are lost to erosion, and it’s not uncommon!
There are two main types of erosion, wind erosion, and water erosion. The one most important factor in water erosion is the how much of the ground is covered by plants, otherwise is known as plant cover. The more of the ground that is covered by plants is good, because the roots hold the soil in place.
If all the top soil is washed away it will leave a poor sub soil(see key). The cultivation of sloped areas isn’t a very good idea: for when it rains the top soil will be washed away. This will from rills(see key) and then gulleys (see key). This problem is made worse by farmers using plows on their soil.
Wind erosion isn’t like water erosion. Wind erosion tends to take its toll almost unnoticeably. Dust particles smaller than a 1000th of a dust micron, fly through the air and kill plant life and damage land
(called PM10’s). The damage these PM10’s do to crops and plant is tremendous
So what can we do to protect our houses and crops? These are questions that are being researched now, so that we may be able to prevent wind and water erosion in the future.
The following was taken from a web site:
Wind erosion directly impacts growers through replanting costs, reduced yields due to crop damage and lost soil productivity over time. Blowing dust creates reduced visibility effecting traffic safety. Deposition of dust in road-side ditches also increases road maintenance costs. Increases surface water pollution can also result from the accumulation of eolian material in surface runoff.
Air quality has become a public issue in the Western US and the Pacific Northwest (PNW) in recent years. Health-related concerns about the effects of fine particulates in blowing dust has added to the potential off-site impacts of wind erosion. The 1990 Federal Clean Air Act made states responsible for monitoring and controlling the amount of small air-borne particulates known as PM10 or particulate matter less than 10 microns in aerodynamic diameter. These particles, about 1/7th the diameter of a human hair, are small enough to be taken into the body's respiratory system. PM10 has been implicated in either causing or exacerbating existing respiratory problems. Children, the elderly and those persons with respiratory disease appear most affected.
Wind Erosion and Fugitive Emission Processes
Soil grain motion and, hence, grain transport, rely on interactions between the grains and the passing airflow. There are three primary modes of grain transport: surface creep, saltation and suspension. Initial motion is achieved when induced aerodynamic forces exerted on a grain become instantly greater than the adhesive forces attaching them to the surface. Grains that are able to be lifted by the air stream but which fall back to the surface after a 'short' distance are traveling in saltation. Soil aggregates and particles larger than ~1000 microns cannot be picked up by the wind but tend to roll along the surface due to wind forces and impacting grains. These grains are moving by creep. Grains less than 20-30 microns are small enough to respond to turbulent fluctuations in the air stream and their motion is defined by turbulent diffusion. These grains are traveling by suspension and may remain airborne until rain washes them out of the air, often being deposited many kilometers downwind. Saltating grains are potentially most damaging to crops. Impact energy can be high particularly in high winds causing leaf and stem damage to young plants. Additionally, impacting grains are a primary method through which PM10-sized particles are suspended into the air stream. Though only a small fraction of total transport, suspended particles impact visibility, often kilometers downwind of their entrainment point, reduces soil productivity over time and contributes to health-related imparements in animals and humans alike.
Surface stability, and therefore resistance to erosion, is related to three primary factors. These are:
Although factors 1 and 3 are outside of human control, growers have learned to adapt cropping systems which are compatible with the climate regime. It is in this area that growers can alter the susceptibility of a particular soil to wind erosion processes. Conservation tillage techniques can decrease erosion susceptibility where as more traditional farming methods often enhance soil erodibility. In the PNW, reductions in soil erodibility have been accomplished most readily through timely tillage practices that promote rough field surfaces and maintain maximum residue cover. Planting cover crops to protect vulnerable surfaces are also used as a control measures in irrigated lands.
Research Alternatives for Reducing Fugitive Emissions
As research continues to unfold, growers are being offered more economical management options to ensure their continued survival. These options include increasing cropping intensity designed to reduce the duration of the summer fallow period when most fugitive emissions occur. The goal is to offer crop yields that are similar to or greater than those obtained from traditional farming techniques with less passes over the field. In another experiment, an increase in the depth of both primary tillage and subsequent rodweedings appear to increase the size of surface clods promoting a rougher surface. This has been accomplished with no loss in surface residue. Experiments are also being conducted to look at viable annual crop rotations in the summer fallow-winter wheat zones of the Columbia Plateau. Possible new crops include annual spring wheat, spring barley and alternating spring wheat and a grain legume. The study is looking at both grain yields and residue production. Additional studies address agronomic impacts of row spacings, weed competition, tillage effects on residue from numerous crops and developing proper application rates for fertilizers and other chemicals.
Many dryland fields in the PNW contain small spots or strips that are more susceptible to wind erosion than neighboring ground. Soils in these 'critical areas' are usually ashy, sandy or calcareous and generally lack any soil structure. It is in these areas that saltation will be initiated providing the a hot zone of particle activiety that can cause large sections of a field to blow. In an effort to control the critical ground from blowing, researchers are applying binding agents to the soil in an attempt to control erodibility. Research is ongoing.
Developing stategies for returing land in the Conservation Reserve Program (CRP) to crop production is a major emphasis of the CP3 project. There are approximately 2.5 million acres of CRP lands in the PNW, with 1 million acres in Washington State alone. It is estimated that about 90% of all CPR acreage will be returned to production after contracts expire, beginning with about 500,000 acres due to expire in fall of 1996. Much of these lands are located in the 8 to 14 inch precipitation zone and are susceptible to wind erosion. The Washington State CRP takeout program was initiated in 1994 to identify Best Management Practices (BMPs) for returning CRP lands to crop production. There are three major research areas in this effort:
This research is being carried out using farm-scale equipment on large, replicated plots. So far, eleven field experiments are underway in seven counties with additional trials being considered. Most trials are between 15 to 20 acres and are designed to allow tillage intensities with resulting residue levels to be comparatively evaluated. Research is continuing.
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