英语专业四级听写021

Passage 21
Soils
There are many different kinds of soils. Different soils have different types of rock and minerals in them than other. Some soils have more water in them than others. Some soils might have more plant and animal material in them, too.
Different kinds of soils are found in different parts of the world. There are several kinds of soils found in the United States. In some areas, the soil has a lot of clay. Other soils are very sandy. Loam¹ is a kind of soil that has a good mixture of clay and sand.
In some places, soil layers are very thick. Lots of plants grow in places with a thick soil layer. In dry and windy places soil layers are much thinner. Layers of soil on mountains are thin because gravity pulls the soil downhill.
The type of soil in a particular place affects what kinds of plants can grow there. (150 words)

1 loam   

n.沃土

参考例句：

• Plant the seeds in good loam.把种子种在好的壤土里。
• One occupies relatively dry sandy loam soils.一个则占据较干旱的沙壤土。