(46) U.S. farmers are planting more acres of crops using soil building and pollution fighting faming systems than traditional me

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问题     (46) U.S. farmers are planting more acres of crops using soil building and pollution fighting faming systems than traditional methods that rely on the plow or intensive  tillage, according to a report due to be released early next month.
    The report, titled "National Crop Residue Management Survey," shows a 6 million acre gain for environmentally friendly farming systems this year.
    (47) It also shows traditional farming methods, which result in greater soil erosion and run off from fields, declined by 4 million acres.
    (48) The survey, conducted on a county-by-county basis by USDA Natural Resources  Conservation Service, indicates that farmers in Iowa, Illinois, South Dakota, Kansas, and Indiana contributed the most to the increase in acres grown with environmentally  friendly farming systems known as conservation tillage systems.
    These states accounted for 5 million of the 6 million acre increase in conservation tillage this year.
    All conservation tillage systems, such as no-till, mulch-till, ridge-till, strip-till, and zone-till, rely on less tillage or less soil disturbance to plant and manage crops.
    Farmers who use these systems leave plant materials stems, stalks, and leaves—on the surface of fields after harvest.
    The plant materials, also called crop residues, serve as a blanket to protect the soil from erosion.
    The crop residues slowly decompose to add organic matter to the soil much like mulching or composting add organic matter to a garden.
    The survey results for 1997 indicate that conservation tillage systems now account for 109.8 million acres or fully 37 percent of the 294.6 million annually planted cropland acres in the United States.
    In the meantime, traditional systems that rely on the plow or intensive tillage fell to 107.6 million acres this year.
    The remaining acres are in an intermediate farming system known as reduced till.
    (49) The head of the nonprofit center that compiles and publishes the annual survey is calling on consumers and farmers alike to focus increased attention on conservation tillage systems.
    "(50) Independent research and practical application across the country show that these systems not only replenish and build organic matter in the soil for improved fu ture food productivity but they will also protect water quality and enhance wild life and the environment for future generations," says John Hebblethwaite, executive director of the Conservation Technology Information Center. "There is also growing evidence that these systems can even help us combat the potential for global warming," he adds.
    Conservation tillage has long been credited for protecting water quality by reducing runoff from farm fields, according to Hebblethwaite.
    He notes the latest research also indicates that soil enriched by crop residues offers  natural protection for groundwater.
    Conservation tillage systems save the farmer money by reducing trips through the field for planting and cultivation.

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答案报告还显示,采用传统耕作法耕种的土地面积减少了四百万英亩,采用传统耕作法会导致土壤的严重侵蚀和水土流失。

解析     句子的框架是It also shows traditional farming methods,…declined by 4 million acres。句中首先包含了一个宾语从句,主语it指上文的report,从句中又套了一个which引导的非限定性定语从句,修饰traditional farming methods。另外注意decline by是“降低了……幅度”的意思,它不同于decline to(降低到……地步);result in意为“导致”。
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