VOA慢速英语20060221a

AGRICULTURE REPORT - Legumes: Good for People and SoilBy Bob Bowen

Broadcast: Tuesday, February 21, 2006

I'm Steve Ember with the VOA Special English Agriculture Report.

Many different kinds of plants are part of the leguminosae group. They are called legumes. These plants can produce their own nitrogen¹. Beans are legumes. Peanuts are legumes. Alfalfa is a legume. There are also many different kinds of trees that are legumes.

As a food, beans are high in protein. Most beans also contain a lot of nutrients² such as calcium³, iron, phosphorus and niacin. Some beans contain amino acids⁴ and lysine.

Many farmers around the world know the value of growing legumes along with their main crops, or between harvests. The legumes replace nitrogen used by crops. They also provide a cover for the soil to help protect it from heavy rains and strong winds.

The roots of the legume plants hold the soil in place. This keeps the soil from being blown away by the wind or washed away by rain. The roots also loosen⁵ the soil. This lets the rain reach deep into the ground.

Legumes produce nitrogen through a process involving bacteria in the soil and nitrogen in the air. The bacteria form small growths on the plant roots. These growths are called nodules. They capture⁶ the atmospheric⁷ nitrogen that has entered the soil.

The nodules change the nitrogen into ammonia, a form of nitrogen that plants can use. The process is called nitrogen fixation. The bacteria needed for the process, rhizobia or frankia, are found in most soils. But if they are not present in the soil in a field, they can be painted on the legume seeds before the seeds are put in the ground. A local agriculture agent can show how to do this.

When planted next to fields, legume trees will add nitrogen to the soil. They provide shade and protect young crop plants from the heat of the sun. They provide firewood. And their wood can be used as building material. Some legume trees also provide medicines and chemicals for coloring cloth.

This VOA Special English Agriculture Report was written by Bob Bowen. Read and listen to our reports at www.unsv.com. I'm Steve Ember.

1 nitrogen   

n.[化]氮

参考例句：

• The atmosphere consist of more than 70% of nitrogen.大气中含有70%以上的氮气。
• What is the percentage of nitrogen in air?空气中所含的氮的比例是多少？

2 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

3 calcium   

n.钙(化学符号Ca)

参考例句：

• We need calcium to make bones.我们需要钙来壮骨。
• Calcium is found most abundantly in milk.奶含钙最丰富。

4 acids   

n.酸( acid的名词复数 )；酸味物质

参考例句：

• Some acids are strong enough to burn the wood. 有些酸的酸性强得可以烧坏木头。 来自《简明英汉词典》
• There are many amino acids that the body cannot synthesise itself. 有许多种氨基酸人体自身不能合成。 来自《简明英汉词典》

5 loosen   

vt.放松，松开，解除（便秘等），放宽；vi.变松，松弛

参考例句：

• I must take some exercise and loosen up my muscles.我必须活动活动使肌肉放松些。
• The medicine may loosen your cough.这种药能减轻你的咳嗽。

6 capture   

vt.捕获，俘获；占领，夺得；n.抓住，捕获

参考例句：

• The company is out to capture the European market.这家公司希望占据欧洲市场。
• With the capture of the escaped tiger,everyone felt relieved.逃出来的老虎被捕获后，大家都松了一口气。

7 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。