How does the terracing shown in this photo prevent soil erosion?
Terracing keeps the soil from moving very far downhill since it will only get as far as the next terrace downhill. Water will also be slowed by the terraces and so will be less able to carry tremendous amounts of soil downhill. Terracing is a great way to preserve soil when farming is being done on hillsides.
A farmer and his sons walk through a dust storm in Cimarron County, Oklahoma in 1936.
Bad farming practices and a return to normal rainfall levels after an unusually wet period led to the Dust Bowl. In some regions more than 75% of the topsoil blew away. This is the most extreme example of soil erosion the United States has ever seen.
Still, in many areas of the world, the rate of soil erosion is many times greater than the rate at which it is forming. Drought, insect plagues, or outbreaks of disease are natural cycles of events that can negatively impact ecosystems and the soil, but there are also many ways in which humans neglect or abuse this important resource. Soils can also be contaminated if too much salt accumulates in the soil or where pollutants sink into the ground.
One harmful practice is removing the vegetation that helps to hold soil in place. Sometimes just walking or riding your bike over the same place will kill the grass that normally grows there. Land is also deliberately cleared or deforested for wood. The loose soils then may be carried away by wind or running water.
Soil is only a renewable resource if it is carefully managed. There are many practices that can protect and preserve soil resources.
Adding organic material to the soil in the form of plant or animal waste, such as compost or manure, increases the fertility of the soil and improves its ability to hold on to water and nutrients (Figure below). Inorganic fertilizer can also temporarily increase the fertility of a soil and may be less expensive or time consuming, but it does not provide the same long-term improvements as organic materials.
Organic material can be added to soil to help increase its fertility.
Preventing Soil Erosion
Soil is a natural resource that is vitally important for sustaining natural habitats and for growing food. Although soil is a renewable resource, it is renewed slowly, taking hundreds or thousands of years for a good fertile soil to develop.
Most of the best land for farming is already being cultivated. With human populations continuing to grow, it is extremely important to protect our soil resources. Agricultural practices such as rotating crops, alternating the types of crops planted in each row, and planting nutrient-rich cover crops all help to keep soil more fertile as it is used season after season. Planting trees as windbreaks, plowing along contours of the field, or building terraces into steeper slopes will all help to hold soil in place (Figure below). No-till or low-tillage farming helps to keep soil in place by disturbing the ground as little as possible when planting.
Steep slopes can be terraced to make level planting areas and decrease surface water runoff and erosion.
The rate of topsoil loss in the United States and other developed countries has decreased recently as better farming practices have been adopted. Unfortunately, in developing nations, soil is often not protected.
Table below shows some steps that we can take to prevent erosion. Some are things that can be done by farmers or developers. Others are things that individual homeowners or community members can implement locally.
|Source of Erosion||Strategies for Prevention|
|Agriculture||Leave leaf litter on the ground in the winter.|
|Grow cover crops, special crops grown in the winter to cover the soil.|
|Plant tall trees around fields to buffer the effects of wind.|
|Drive tractors as little as possible.|
|Use drip irrigation that puts small amounts of water in the ground frequently.|
|Avoid watering crops with sprinklers that make big water drops on the ground.|
|Keep fields as flat as possible to avoid soil eroding down hill.|
|Grazing Animals||Move animals throughout the year, so they don’t consume all the vegetation in one spot.|
|Keep animals away from stream banks, where hills are especially prone to erosion.|
|Logging and Mining||Reduce the amount of land that is logged and mined.|
|Reduce the number of roads that are built to access logging areas.|
|Avoid logging and mining on steep lands.|
|Cut only small areas at one time and quickly replant logged areas with new seedlings.|
|Development||Reduce the amount of land area that is developed into urban areas, parking lots, etc.|
|Keep as much “green space” in cities as possible, such as parks or strips where plants can grow.|
|Invest in and use new technologies for parking lots that make them permeable to water in order to reduce runoff of water.|
|Recreational Activities||Avoid using off-road vehicles on hilly lands.|
|Stay on designated trails.|
|Building Construction||Avoid building on steep hills.|
|Grade surrounding land to distribute water rather than collecting it in one place.|
|Where water collects, drain to creeks and rivers.|
|Landscape with plants that minimize erosion.|
- Soil is a renewable resource, but sometimes it is lost faster than it can be replaced.
- Soil resources must be preserved because there are many more people on Earth who need to eat and a great deal of topsoil has already been lost in many regions.
- There are many techniques available for preventing soil loss in agriculture, grazing, logging, mining, and recreation.
- Soil conservation is extremely important. Some helpful practices include adding organic material, terracing, and no-till farming.
Use this resource to answer the questions that follow.
- http://www.hippocampus.org/Earth%20Science Environmental Science Search: Erosion Control
1. Describe contour farming.
2. What is terracing?
3. How does strip cropping work?
4. What is agroforestry?
5. How does tree litter help crops?
1. Why is it so important for strategies that prevent soil erosion to be understood and used?
2. Which agricultural techniques are better that preserving soils?
3. How do recreational activities exacerbate soil erosion and how can this be lessened?
4. Why does the addition of organic material to soil help with its conservation?
5. What are a few agricultural practices that make conserving soil a priority?