Cover crops

Cover crops 

来源:环球雅思网 www.ielts.com.cn 2005-5-31

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    I'm Gwen Outen with the VOA Special English Agriculture Report.
    Cover crops are an ancient way to help farmers improve their soil and increase their harvests, and these days, save money on chemicals. Scientists like Aref Abdul-Baki search for new and better cover crops. Mr. Abdul-Baki is with the Agricultural Research Service of the United States Department of Agriculture. He works at the Sustainable Agricultural Systems Laboratory in Beltsville Maryland. Mr. Abdul-Baki has found some cover crops to resist ground worms that attack the roots of tomatoes. Sunn hemp, cowpea, and velvet bean are good for warm humid areas. The soil is ploughed to plan the cover crops during the summer months. In the fall, the cover crops are turned over in the soil then the tomatoes are planted. 
    In states with moderate climates like Maryland and Virginia, the cover crops are planted in the fall to grow during early spring. Mr. Abdul-Baki tells us that good cover crops are hairy vetch and rye . 
    To avoid soil loss, the seeds are planted without the use of plowing . In May the cover crops are cut and the remains are left on the surface. The same method can be used for other summer crops like peppers, sweet corn, green beans and some melons. After the cover crop is cut, the result is a layer of organic material. This will help the new crop grow and suppress unwanted plants. The cover crop provides extra nutrients to the soil, it also keeps the soil from drying out, and helps prevent the loss of soil. 
    In hot dry areas like in southern California, cover crops help reduce soil temperatures. They also reduce water loss and erosion. Lanewach is a good cover crop, it is planted in the fall and breaks down without any assistance, it releases it seeds back into the soil. 
    Mr. Abdul-Baki says farmers who use cover crops no longer need to treat their soil with methyl bromide before they plant tomatoes. Methyl bromide kills many kinds of organisms, but Mr. Abdul-Baki notes that the poison also damages the environment and is a health danger. The government restricts the use of methyl bromide and countries have agreed to a treaty to ban it. 
    Aref Abdul-Baki says farmers who use cover crops produces many or more tomatoes per hectare as compare to no use of cover crops. 
    This VOA Special English Agriculture Report was written by MR, our reports are online at voaspecialenglish.com, I'm Gwen Outen.
    Vocabulary: 
    cover crop: a crop, such as winter rye or clover, planted between periods of regular crop production to prevent soil erosion and provide humus or nitrogen.（
间作在常规农作物生长间期内种植的农作物，比如冬麦或三叶草，以预防土壤侵蚀并能提供腐殖质和氮）
    hairy vetch: 毛苕子

    rye: a cereal grass (Secale cereale) widely cultivated for its grain.（黑麦，因其谷粒而广泛种植的一种可食用草）

    plowing: 耕作

    methyl bromide: 甲基溴，溴化甲烷