VOA慢速英语--为了你的植物 请少用点盐

In the United States, people often use large amounts of salt to remove dangerous ice from roads and walkways in the winter. But when the spring arrives, all that salt can really damage plants in the garden. Salt is the chemical sodium¹ chloride.

Salt pulls water from living cells, like plant roots and the healthy ground soil around them. So, spring growth may show up lighter² in color than normal, or, in the worst cases, plants may simply die.

Rain can wash away much of the salt, permitting some older plants to live. Salt can also be removed by pouring a large amount of water on the ground where plants are growing. But the best action is to simply use less salt.

Researchers have found that putting a small amount of salt on a road works better to melt ice than dropping a large amount of salt crystals.

Different salts

There are, of course, other things that can be used in place of sodium chloride. One is the chemical calcium³ chloride. It does less damage to plants and melts ice faster than salt. It also works when the temperature is below negative 17 degrees Celsius⁴. Salt loses some of its effectiveness at temperatures below negative 12 degrees.

Still, calcium chloride does put chloride ion, which plants don't like, into the soil. It is also more expensive and can do more damage to cars.

Man-made chemical fertilizers are all salts. So why not use them to remove ice from the roads?

Well, they are even more costly⁵, and they only work at negative 6 degrees Celsius.

Calcium magnesium⁶ acetate, also called CMA, has become a popular alternative. It is made by combining limestone⁷, a type of rock, and vinegar. It breaks down naturally so it does not damage plants or soil. It stays on roads and does not hurt cars.

CMA does have problems, however. It is most effective at around negative 9 Celsius, just like salt. And it is better at stopping ice from forming rather than removing it. So, it is best placed on a road before the temperature gets very cold.

Some materials other than salt - such as sand or very small pieces of wood - can also work against ice. But they can be very messy.

Use a holistic⁸ system

The best way to remove ice is through a holistic method. This involves using a combination of materials, such as salt and a bit of sand. If this mixture is used before ice forms, less is needed as the weather gets colder.

When placing plants in the ground near a road or where a car is parked, it is best to use common sense: choose a plant that is not badly affected⁹ by salt. Plants that are native to the seashore can usually stand up well to salt, like Rosa rugosa, a common beach rose.

Other examples of trees and plants that can resist the effects of salt include silver maple¹⁰, honey and black locusts¹¹, poplar, junipers, lilac and Colorado blue spruce.

Words in This Story

crystal – n. a small piece of a substance that has many sides and is formed when the substance turns into a solid

ion – n. an atom or group of atoms that has a positive or negative electric charge from losing or gaining one or more electrons

fertilizer – n. a substance or a special chemical that is added to soil to help the growth of plants

alternative – n. offering or expressing a choice

vinegar – n. a sour liquid that is used to flavor or preserve foods or to clean things

holistic – adj. relating to or concerned with complete systems rather than with individual parts

park – v. leaving a car at a specific place

1 sodium   

n.（化）钠

参考例句：

• Out over the town the sodium lights were lit.在外面，全城的钠光灯都亮了。
• Common salt is a compound of sodium and chlorine.食盐是钠和氯的复合物。

2 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

3 calcium   

n.钙(化学符号Ca)

参考例句：

• We need calcium to make bones.我们需要钙来壮骨。
• Calcium is found most abundantly in milk.奶含钙最丰富。

4 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

5 costly   

adj.昂贵的，价值高的，豪华的

参考例句：

• It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
• This dictionary is very useful,only it is a bit costly.这本词典很有用，左不过贵了些。

6 magnesium   

n.镁

参考例句：

• Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
• The water contains high amounts of magnesium.这水含有大量的镁。

7 limestone   

n.石灰石

参考例句：

• Limestone is often used in building construction.石灰岩常用于建筑。
• Cement is made from limestone.水泥是由石灰石制成的。

8 holistic   

adj.从整体着眼的，全面的

参考例句：

• There is a fundamental ambiguity in the use of word "whole" in recent holistic literature.在近代的整体主义著作中，“整体”这个词的用法极其含混。
• In so far as historicism is technological,its approach is not piecemeal,but "holistic".仅就历史决定论是一种技术而论，它的方法不是渐进的，而是“整体主义的”。

9 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。

10 maple   

n.槭树，枫树，槭木

参考例句：

• Maple sugar is made from the sap of maple trees.枫糖是由枫树的树液制成的。
• The maple leaves are tinge with autumn red.枫叶染上了秋天的红色。

11 locusts   

n.蝗虫( locust的名词复数 )；贪吃的人；破坏者；槐树

参考例句：

• a swarm of locusts 一大群蝗虫
• In no time the locusts came down and started eating everything. 很快蝗虫就飞落下来开始吃东西，什么都吃。 来自《简明英汉词典》