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| AGRICULTURE REPORT - Soil Conservation Methods |
| 2003年09月01日14:49:24 网易教育 By Gary Garriott |
Broadcast: July 29, 2003
This is the VOA Special English Agriculture Report.
Soil conservation efforts protect soil from wind and water that can blow or wash it away. Good soil produces food crops for both people and animals.
One important form of soil conservation is the use of windbreaks. Windbreaks are barriers formed by trees and other plants with many leaves. Farmers plant them in lines around their fields. Windbreaks stop the wind from blowing soil away. They also keep the wind from destroying or damaging crops. They are very important for growing grains, such as wheat.
For example, in parts of West Africa, studies have shown that grain harvests can be twenty per cent higher on fields protected by windbreaks compared to those without such protection.
Windbreaks are effective when a wall of trees and other plants blocks the wind. The windbreaks should also limit violent motions of the wind to those areas closest to the windbreak.
However, windbreaks seem to work best when they allow a little wind to pass through. If the wall of trees and plants stops wind completely, then violent air motions will take place close to the ground. These motions cause the soil to lift up into the air where it will be blown away. For this reason, a windbreak is best if it has only sixty to eighty per cent of the trees and plants needed to make a solid line.
An easy rule to remember is that windbreaks can protect areas up to ten times the height of the tallest trees in the windbreak.
There should be at least two lines in each windbreak. One line should be large trees. The second line, right next to it, can be shorter trees and other plants with leaves.
Windbreaks not only protect land and crops from the wind. They can also provide wood products. These include wood for fuel and longer pieces for making fences. Locally-grown trees and plants are best for windbreaks.
You can get more information about windbreaks and other forms of soil conservation from the group Volunteers in Technical Assistance. VITA is an organization that helps people around the world use science and technology to solve problems.
VITA is on the Internet at www.vita.org.
This Agriculture Report was written by Gary Garriott.
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