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This is the VOA Special English Agriculture Report.

Planting trees around poultry farms can improve air and water quality -- and please the noses of neighbors.

Scientists have shown that just three rows of trees near poultry houses can reduce the release of dust and ammonia. Trees can also reduce the strong odor of ammonia gas.

The trees capture dust, ammonia and odors in their leaves. They can also reduce energy use. They provide shade from the sun, reducing cooling costs in the summer. And they act as a windbreak, reducing heating costs in winter.

Scientists say the trees can also improve water quality around farms by removing pollutants from soil and groundwater.

Several years ago, in the eastern United States, people were objecting to the odor of poultry farms on the Delmarva Peninsula. Delmarva is where the states of Delaware, Maryland and Virginia come together. Each of the two thousand farms there can house an average of seventy-five thousand chickens.

Traditionally the farms used windows to provide fresh air in the chicken houses. Farmers rarely planted trees or tall crops around the buildings, so there would be no barrier to the airflow.

But then farms began to use new ventilation systems. Instead of windows, the new systems used tunnel fans to circulate air. The fans directed airflow from the poultry houses toward the homes of neighbors.

A team led by George Malone at the University of Delaware began dealing with the problem in the year 2000. The team recently presented a report at the national meeting of the American Chemical Society in Washington, D.C.

Over a period of six years, the scientists found that planting three rows of trees reduced total dust and ammonia by more than half. And they say the trees reduced odors by eighteen percent.

For the first row nearest the fans, they generally suggest using trees that lose their leaves in the fall or trees with waxy leaf surfaces. They suggest evergreen trees for the other two rows. Some trees work better than others. And what works in one area of the country may not work as well in other places.

Farmers may think trees will take too long to grow to be effective. But some trees can grow as fast as three meters a year.

Today, one-third of the Delmarva farms have planted trees, technically known as vegetative environmental buffers. These buffers can offer a way to cut pollution, save money and make the neighbors happy.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. I'm Jim Tedder.

ammonia gas:氨氣

ventilation system:通風(fēng)系統(tǒng)

(Source: VOA 英語(yǔ)點(diǎn)津姍姍編輯)