When is a plant considered a weed? Experts at Penn State University have a simple answer: When the undesirable qualities outweigh the good qualities.
Consider the fact that crops generally produce several hundred seeds from each plant. By comparison, 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.
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. Dense 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 suppressing weeds is dense planting.
He says a dense, competitive 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 or covering them with mulch made of shredded 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 deeply or make them into mulch.
Professor Curran says another way to make use of weeds is to compost them. Heat is produced in the process of making organically rich compost to improve soil. The heat will kill many, though not all, weed seeds. The same is true for seeds that pass through animals that graze on weeds.
美国“困难时期”大曝光:30万人不愿谈工资
猫和狗谁更聪明?
《科尼2017》制作人因高压裸奔?
考研英语泄题 复试加难度测可疑考生
林书豪签约沃尔沃 林疯狂成汽车巨头品牌代言人
执着日本人被GPS成功导入海里
汽柴油价今起每吨涨600元 汽油全面进入8元时代
男子在家中自建总统办公室
员工最想逃离的10大华尔街投行
瑞士公投拒绝六周带薪假期
全球十大亿万富豪城市排名:莫斯科三次问鼎香港第四
卖萌大鲨鱼与潜水员击掌
乌拉圭2名护士展开杀人竞赛 遇害患者多达200人
我曾经是电子产品的致命克星
研究:爱走神的孩子更聪明
震惊世界的美妙迪拜风景
墨西哥南部发生7.6级地震 群众:整个世界在震动
手机来电纹身问世:让你“切身”感受信息
韩国高学历“剩女”难嫁 只能求助婚介所
国内英语资讯:Commissioners office of Chinas foreign ministry in HK lodges representations with U.S. C
事业有成的妈妈产后更忧郁:根本不是计划那样
How to Read 如何阅读
科学家将要用基因编辑技术治疗先天失明
玛丽莲•梦露:永远的性感女神
“中国购物狂”横扫全球霸气不可阻挡
警惕:安眠药或可致人早死
Prada现在用回收的垃圾做包
“重量级”科学研究:肥胖乃是命中注定
遗体竟被用于爆炸试验 那些捐给科研的遗体都去哪了?
沈阳三口之家的厕所生活
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |