广播电视英语短句 第 320 课：肥料使用-1

Fertilizer use differs from country to country, and from too little to too much. 每个国家的肥料使用各不相同，有的太少，有的太多。

Nitrogen and phosphorus can produce big crops. But they can also pollute water and air. 氮素和磷素能够促进作物生长，但是也会污染水和空气。

A recent policy discussion in the journal Science compared the nutrient balances of different agriculture systems. 最近发表在科学期刊上的政策讨论对比了不同农业系统下的养分平衡。

Researchers compared the use of fertilizer in three areas that grow maize as a major grain: China, Kenya and the United States. 研究人员对比了三个以玉米为主要作物的地区的肥料使用情况，分别是中国，肯尼亚和美国。

By two thousand five, they say, farms in northern China produced about the same amount of corn per hectare as farms in the American Midwest. 他们说，截至到2005年，中国北部的农田每公顷的产量与美国中西部相同。