VOA慢速英语2011--Getting to the Root of How to Water Tree

Agriculture Report - Getting to the Root of How to Water Trees

This is the VOA Special English Agriculture Report.
Some trees can survive a long time without water. Think of trees that grow in the desert. But other trees may need more moisture than they can get from rainfall or from the air -- from, say, coastal¹ or mountain fog.
The soil stores moisture during cooler weather. But most of that moisture is gone by the middle or end of the hottest months of the year.
Trees and other plants can look thirsty. Leaves can become droopy and hang downward. They can also turn yellow. Yellowing can be a sign of too much water. But it can also be a warning sign of too little water.
The Vacaville Tree Foundation is a volunteer community group in California. It has advice for watering newly planted trees and established trees.
With a newly planted tree, the roots have not yet spread out from the root ball. The root ball can become dry faster than the dirt around it. So put water on the area of the root ball and the surrounding soil until the roots become established.
Once a tree is well established, water deeply instead of often. The amount of water needed depends on the tree and the soil. Clay soils hold water for longer periods while sandy soils hold less water. During the hottest season, a deep watering may satisfy a tree for anywhere from ten days to four weeks.
Part of skilled watering is knowing to stop when the soil needs a little time to absorb the water. Otherwise the water runs off the surface and gets wasted.
Ted² Swiecki is a plant scientist in California with the Phytosphere Research company and the Vacaville Tree Foundation. He says people should not water established trees at the base of the trunk. This can harm the tree.
Too much water in the soil at the base of a tree can lead to the growth of fungi³. If the area is too wet, harmful organisms have a better chance to invade the tree and cause disease.
Mr. Swiecki says this is true especially in Mediterranean⁴ and semi-dry climates. Many trees in these climates have adapted to having a dry area near their base during the hottest season.
TED SWIECKI: “Water displaces air in the soil. And roots are aerobic⁵; they require oxygen for the soil to function properly. So if you keep the soil saturated⁶ and there’s no air there, and then you are basically starving the roots for oxygen.”
And that’s the VOA Special English Agriculture Report, written by Jerilyn Watson. For more growing advice, and to learn English, go to voaspecialenglish.com. You can also find us on Facebook, Twitter and YouTube at VOA Learning English. I’m Bob Doughty⁷.

1 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

2 ted   

vt.翻晒，撒，撒开

参考例句：

• The invaders gut ted the village.侵略者把村中财物洗劫一空。
• She often teds the corn when it's sunny.天好的时候她就翻晒玉米。

3 fungi   

n.真菌，霉菌

参考例句：

• Students practice to apply the study of genetics to multicellular plants and fungi.学生们练习把基因学应用到多细胞植物和真菌中。
• The lawn was covered with fungi.草地上到处都是蘑菇。

4 Mediterranean   

adj.地中海的；地中海沿岸的

参考例句：

• The houses are Mediterranean in character.这些房子都属地中海风格。
• Gibraltar is the key to the Mediterranean.直布罗陀是地中海的要冲。

5 aerobic   

adj.需氧的，增氧健身法的，有氧的

参考例句：

• Aerobic exercise helps to build up stamina.有氧健身操有助于增强耐力。
• Aerobic dance is conductive to the health.有氧舞蹈有助于健康。

6 saturated   

a.饱和的，充满的

参考例句：

• The continuous rain had saturated the soil. 连绵不断的雨把土地淋了个透。
• a saturated solution of sodium chloride 氯化钠饱和溶液

7 doughty   

adj.勇猛的，坚强的

参考例句：

• Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质：脾气倔强，性格刚强。
• The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。