[ti:Building a Windbreak to Protect Crops] [ar:Jim Tedder] [al:Agriculture Report] [by:www.hxen.com] [00:00.00]如果您也喜欢 恒星英语学习网 www.hxen.com 请与您的朋友分享...This is the VOA Special English [00:02.94]Agriculture Report. [00:05.24]Soil conservation methods [00:07.98]help farmers protect their land [00:10.78]from the damage caused by farming [00:13.36]and the forces of nature. [00:15.66]One method of soil conservation [00:19.25]is the use of windbreaks. [00:21.23]Windbreaks are barriers formed [00:25.37]by trees and other plants. [00:27.86]Farmers plant these barriers [00:30.94]around their fields. [00:32.48]Windbreaks help prevent [00:35.87]the loss of soil. [00:37.11](SOUND) [00:41.29]They stop the wind [00:43.29]from blowing soil away. [00:45.38]They also keep the wind [00:47.97]from damaging or destroying crops. [00:50.60]Windbreaks can be highly valuable [00:54.63]for protecting grain crops. [00:57.18]For example, studies have been done [01:01.46]on windbreaks in parts of West Africa. [01:04.55]These studies found [01:06.94]that grain harvests were as much [01:10.17]as twenty percent higher [01:11.86]in fields protected [01:13.65]by windbreaks compared [01:16.64]to fields without them. [01:18.58]But here is something interesting [01:21.81]about windbreaks. [01:24.07]They seem to work best [01:26.11]when they allow some wind to pass [01:29.94]through the barrier of trees [01:31.58]or plants around a field. [01:34.17]If not, then the movement [01:37.85]of air close to the ground [01:39.64]will lift the soil. [01:41.78]Then the soil will be blown away. [01:45.91]For this reason, [01:48.00]a windbreak works best [01:50.40]if it contains only sixty [01:53.04]to eighty percent of the trees [01:55.88]and plants that would be needed [01:58.51]to make a solid line. [02:00.60]An easy rule to remember [02:03.24]is that windbreaks can protect [02:05.94]areas up to ten times the height [02:09.37]of the tallest trees [02:11.16]in the windbreak. [02:13.30]There should be at least two lines [02:16.69]in each windbreak. [02:19.14]One line should be large trees. [02:22.72]The second line, right next to it, [02:26.85]can be shorter trees [02:29.04]and other plants with leaves. [02:31.48]Locally grown trees and plants [02:35.06]are considered the best choices [02:37.65]for windbreaks. [02:39.54]Studies have shown that [02:42.97]some kinds of trees can grow well [02:46.11]even if the quality of the land [02:48.60]is not very good. [02:50.69]One kind of tree is the white pine. [02:53.82]Another is the loblolly pine. [02:57.41]Windbreaks not only protect land [03:01.00]and crops from the wind. [03:03.09]Surplus trees can be cut down [03:06.47]and used or sold for wood. [03:09.56](SOUND) [03:12.70]Trees reduce the damaging effects [03:15.71]of wind and rain. [03:17.60]Their roots help protect soil [03:20.09]from being washed away. [03:21.88]And trees can provide another [03:25.12]valuable service for agriculture. [03:28.20]They can provide grazing animals [03:30.94]with shade from the sun. [03:33.82]And that's the VOA Special English [03:38.12]Agriculture Report. [03:38.73]You can learn English and stay [03:42.60]informed with our programs [03:45.25]at www.hxen.com. [03:48.14]You can also get more information [03:51.02]about windbreaks and other forms [03:53.41]of soil conservation [03:55.25]at enterpriseworks.org. [03:58.74]I'm Jim Tedder.如果您也喜欢 恒星英语学习网 www.hxen.com 请与您的朋友分享...