[00:00.100]From VOA Learning English,
[00:02.410]this is the Agriculture Report.
[00:04.950]Soil conservation methods help farmers
[00:08.850]protect their land from the damage
[00:11.240]caused by farming and the forces of nature.
[00:15.200]One method of soil conservation
[00:18.320]is the use of windbreaks.
[00:20.680]Windbreaks are barriers formed by trees and other plants.
[00:25.600]Farmers plant these barriers around their fields.
[00:29.450](SOUND)
[00:34.410]Windbreaks help prevent the loss of soil.
[00:37.970]They stop the wind from blowing soil away.
[00:42.330]They also keep the wind from damaging or destroying crops.
[00:48.730]Windbreaks can be highly valuable for protecting grain crops.
[00:54.990]For example, studies have been done on windbreaks
[00:59.550]in parts of West Africa.
[01:01.850]These studies found that grain harvests
[01:05.810]were as much as twenty percent higher in fields protected
[01:11.210]by windbreaks compared to fields without them.
[01:15.470]But here is something interesting about windbreaks.
[01:20.430]They seem to work best when they allow some wind to pass
[01:25.830]through the barrier of trees or plants around a field.
[01:30.440]If not, then the movement of air
[01:33.750]close to the ground will lift the soil.
[01:37.560]Then the soil will be blown away.
[01:41.260]For this reason, a windbreak works best
[01:45.480]if it contains only sixty to eighty percent of the trees
[01:50.930]and plants that would be needed to make a solid line.
[01:55.480]An easy rule to remember is that windbreaks
[02:00.220]can protect areas up to ten times
[02:03.670]the height of the tallest trees in the windbreak.
[02:08.130]There should be at least two lines in each windbreak.
[02:13.350]One line should be large trees.
[02:16.700]The second line, right next to it,
[02:19.970]can be shorter trees and other plants with leaves.
[02:24.600]Locally grown trees and plants
[02:28.150]are considered the best choices for windbreaks.
[02:32.360]Studies have shown that some kinds of trees can grow well
[02:37.760]even if the quality of the land is not very good.
[02:42.710]One kind of tree is the white pine.
[02:46.620]Another is the loblolly pine.
[02:50.330]Windbreaks not only protect land and crops from the wind.
[02:55.870]Surplus trees can be cut down and used or sold for wood.
[03:02.890](SOUND)
[03:05.790]Trees reduce the damaging effects of wind and rain.
[03:11.050]Their roots help protect soil from being washed away.
[03:15.890]And trees can provide another valuable service for agriculture.
[03:22.150]They can provide grazing animals with shade from the sun.
[03:27.260]And that's the Agriculture Report from VOA Special English.