www射-国产免费一级-欧美福利-亚洲成人福利-成人一区在线观看-亚州成人

This is the VOA Special English Agriculture Report.

Weeds compete with plantings for water and nutrients. So farmers and gardeners may have good reason to hate them. But weeds can also bring pretty flowers and wild beauty to places lacking either. British nature writer Richard Mabey offers support for them in his new book. The title says it all: "Weeds: In Defense of Nature's Most Unloved Plants."

But when exactly is a plant considered a weed? Experts at Penn State University say the answer is simple: when the undesirable qualities outweigh the good qualities.

A crop plant generally produces several hundred seeds. But a weed plant can produce tens or even hundreds of thousands of seeds. And if seeds get buried, they may survive for many years underground.

Eradicating 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 suppress weed growth. But so can dense planting. Bill Curran is a professor of weed science at Penn State. He says a dense, competitive crop that quickly shades the soil from the sun will help reduce weed growth.

Other controls include turning over the soil, pulling the weeds or covering them with mulch made of wood, garden waste or other material.

But even mulch has its limits. Natural resource specialists point out that weeds can be transported in mulch. This is also true of soil, grain, hay and animals.

Yet animals like sheep or goats eat weeds, so they can provide a biological control. 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.

Some people burn weeds or bury them deep in the ground or make them into mulch.

Professor Curran says another way to make use of weeds is to compost them. The process of making organically rich compost produces heat. This heat kills many, though not all, weed seeds. The same is true for seeds that pass through animals that graze on weeds.

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

nutrient: a substance that provides nourishment essential for growth and the maintenance of life 營養物,滋養物

eradicate: to destroy or get rid of something completely, especially something bad 根除；消滅；杜絕

gluten: a sticky substance that is a mixture of two proteins and is left when starch is removed from flour, especially wheat flour 谷蛋白；面筋

mulch: material, for example, decaying leaves, that you put around a plant to protect its base and its roots, to improve the quality of the soil or to stop weeds growing 覆蓋物，護根（用以保護植物根基、改善土質或防止雜草生長）

Related stories:

Inventor of weed eater started a revolution

Grow it yourself: onions are nothing to cry about

Beauties in the garden: growing ornamental trees and bushes

The seeds of weed control

（來源：VOA 編輯：實習生高美）