This is Shep O'Neal with the VOA Special English Agriculture
Report.
Farmers
use different kinds of soil conservation methods to protect their land from
damage by farming and the forces of nature. 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.
There have been studies done on windbreaks in parts of West Africa, for
example. These found that grain harvests can be twenty percent higher in fields
protected by windbreaks compared to fields without such protection.
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 60 to 80 percent
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. Locally grown trees and plants are best for windbreaks.
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.
You can get more information about windbreaks and other forms of soil
conservation from the group Volunteers in Technical Assistance. VITA, now part
of EnterpriseWorks/VITA, is on the Web at vita.org.
Internet users can read and listen to our Agriculture Reports at
voaspecialenglish dot com. And if you have a question, send it to
special@voanews.com. Make sure to include your name and tell us where you are
from. We might be able to answer your question on the air, but please know that
we cannot answer questions personally.
This VOA Special Agriculture Report was written by Gary
Garriott. I'm Shep O'Neal.
windbreak :
防風(fēng)林
