AGRICULTURE REPORT - Wood Chips Protect Waterways

13 May 2002, 14:14 UTC
AGRICULTURE REPORT
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May 14, 2002: Wood Chips Protect Waterways

By George Grow

This is the VOA Special English AGRICULTURE REPORT.

American scientists are developing ways to limit pollution from agricultural fertilizers in rivers and other
waterways. The scientists say they found one method that provides a natural line of defense¹. Their method
involves small pieces of wood called wood chips.

The scientists buried a large amount of wood chips near crops treated with nitrate
fertilizer. They found that the areas filled with wood chips reduced the nitrate in the
water by as much as seventy percent.

Dan Jaynes of the United States Agricultural Research Service is leading the study.
He works at the Soil and Water Quality office in Ames, Iowa.

In the United States, devices called drainage tiles can speed the removal of extra
water from cropland. Farmers build drainage tiles near their fields. The devices help
direct unneeded water to nearby waterways. Mister Jaynes notes that farmers use drainage tiles on thirty percent
of all cropland in the central United States.

However, when water is removed from fertilized² crops, nitrate may not reach deep into the soil. As a result, the
fertilizer cannot help plant roots. Often the nitrate fertilizer is washed into rivers and other waterways. It feeds the
growth of underwater plants. As the plants die and break down, they use up all the oxygen in the water. This
causes a condition known as hypoxia. Plants and animal life cannot live in the water if it does not contain enough
oxygen. High levels of nitrate have also caused problems for communities that use rivers for drinking water.

The American scientists carried out their experiment on land with corn and soybean crops. They dug large holes
around the fields. These trenches³ are two meters deep and about two-thirds of a meter wide. They extend in the
same direction as the drainage tiles.

The scientists filled the trenches with wood chips up to about one-third of a meter below the surface. Then they
covered the chips with soil.

The wood chips create a natural barrier that helps change nitrate into nitrogen gas, which is common in the
atmosphere. Mister Jaynes says the method works equally well for small and large farms. He said farmers do not
need to supervise the system.

The scientists now will study how long the wood chips are effective before they break down.

This VOA Special English AGRICULTURE REPORT was written by George Grow.

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1 defense   

n.防御，保卫；[pl.]防务工事；辩护，答辩

参考例句：

• The accused has the right to defense.被告人有权获得辩护。
• The war has impacted the area with military and defense workers.战争使那个地区挤满了军队和防御工程人员。

2 Fertilized   

v.施肥( fertilize的过去式和过去分词 )

参考例句：

• The study of psychology has recently been widely cross-fertilized by new discoveries in genetics. 心理学研究最近从遗传学的新发现中受益匪浅。
• Flowers are often fertilized by bees as they gather nectar. 花常在蜜蜂采蜜时受粉。

3 trenches   

深沟，地沟( trench的名词复数 )； 战壕

参考例句：

• life in the trenches 第一次世界大战期间的战壕生活
• The troops stormed the enemy's trenches and fanned out across the fields. 部队猛攻敌人的战壕，并在田野上呈扇形散开。