VOA慢速英语2009-Agriculture Report - The Seeds of Weed Control

This is the VOA Special English Agriculture Report.

When is a plant considered a weed? Experts at Penn State University have a simple answer: When its undesirable¹ qualities outweigh² its good qualities.

Consider this: Crops generally produce several hundred seeds per plant. But each weed plant can produce tens or even hundreds of thousands of seeds. And some buried seeds can survive up to forty years, or even longer.
　
Horseweed, which has become resistant³ to chemical weed killers⁴

Eradicating⁵ weeds means that you have to remove all the seeds and roots so the plants will not grow back. But birds or the wind can reintroduce them to the land.

A more common way to deal with weeds is to control them enough so that the land can be used for planting. Experts advise using two or more control methods to deal with weeds.

Chemical weed killers or natural treatments like corn gluten can suppress⁶ weed growth. Dense⁷ planting of a crop can also act as a natural control.

Bill Curran is a professor of weed science at Penn State, in University Park, Pennsylvania. He says one of the most common methods for suppressing⁸ weeds is dense planting.

He says a dense, competitive⁹ crop that quickly shades the soil will help suppress many weeds. The seeds need light to grow, so blocking the sun will reduce weed growth.

Other controls include turning over the soil, pulling the weeds by hand or covering them with mulch made from wood, garden waste or other material. Mulch is widely used, but even mulch has its limits.

Natural resource specialists in the Queensland government in Australia note that weeds can be transported in mulch. This is also true of soil, grain, hay and animals.

Yet animals like sheep or goats can provide a biological control -- they eat weeds. Insects and other organisms can also act as biological controls.

Preventing the spread of weeds is an important part of weed management. Farm vehicles should be kept out of areas with weeds. If that is not possible, then clean off the equipment and your shoes when leaving.

People in Queensland are advised to take weeds and garden waste to a waste center or burn them, bury them deeply or make them into mulch.

Professor Curran says composting weeds is another way to make use of them. The process of making organically rich compost produces heat. The heat will kill many, though not all, weed seeds. The same is true of seeds that pass through farm animals that graze¹⁰ on weeds.

And that's the VOA Special English Agriculture Report, written by Jerilyn Watson. Archives are at voaspecialenglish.com. I'm Steve Ember.

1 undesirable   

adj.不受欢迎的，不良的，不合意的，讨厌的；n.不受欢迎的人，不良分子

参考例句：

• They are the undesirable elements among the employees.他们是雇员中的不良分子。
• Certain chemicals can induce undesirable changes in the nervous system.有些化学物质能在神经系统中引起不良变化。

2 outweigh   

vt.比...更重，...更重要

参考例句：

• The merits of your plan outweigh the defects.你制定的计划其优点胜过缺点。
• One's merits outweigh one's short-comings.功大于过。

3 resistant   

adj.(to)抵抗的，有抵抗力的

参考例句：

• Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
• They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。

4 killers   

凶手( killer的名词复数 )； 消灭…者； 致命物； 极难的事

参考例句：

• He remained steadfast in his determination to bring the killers to justice. 他要将杀人凶手绳之以法的决心一直没有动摇。
• They were professional killers who did in John. 杀死约翰的这些人是职业杀手。

5 eradicating   

摧毁，完全根除( eradicate的现在分词 )

参考例句：

• Objective: To study the acute and chronic toxicity of Ten-flavor-acne eradicating-capsule. 目的：探讨复方中药合剂十味平痤胶囊的急性及慢性毒性。
• We are on the verge of eradicating polio in the world. 我们已在世界消除小儿？痹症的边缘了。

6 suppress   

vt.压制，镇压，查禁，抑制，阻止

参考例句：

• He continued to suppress the people and serve the imperialists.他继续镇压人民，为帝国主义效劳。
• She was struggling to suppress her sobs.她拼命不让自己哭出来。

7 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

8 suppressing   

抑制（感情等）( suppress的现在分词 )； 压制； 禁止发表； 阻止…的生长（或发展）

参考例句：

• They had already posed the obviousquestions he was suppressing. 他们早就提出了他避而不谈的那些明显的问题。
• The guilty president was suppressing the catastrophic news. 应该承担罪责的总统扣压着这个灾难性消息。

9 competitive   

adj.竞争的，比赛的，好竞争的，有竞争力的

参考例句：

• Some kinds of business are competitive.有些商业是要竞争的。
• These businessmen are both competitive and honourable.这些商人既有竞争性又很诚实。

10 graze   

v.(牲畜)吃草；放牧；擦过(牲畜)；n.擦伤

参考例句：

• There is good grassland here for your cattle and horses to graze on.这里有很好的草地供你们放牧牛马。
• Nothing serious.Just a graze.没关系，就破了一点皮。