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The texture of the soil depends on the relative amounts of different
sized particles that combine to make up the soil. These particles
can be as small as clay. A typical clay soil is composed of approximately
60 percent actual clay, 20 percent silt, and 20 percent sand. The
5 particles in a clay soil are so fine that it tends to be compact
and interferes with the oxygen supply for plant roots. Water has
trouble entering this impervious soil, and runoff is very common
during rainfalls. A typical light sandy soil is composed of approximately
70 percent sand, 20 percent silt, and 10 percent clay. The particles
10 in a sandy soil are comparatively large, permitting water to enter
the soil and to pass through it so quickly that it often carries
nutrients with it and dries out very rapidly. The texture of sandy
soils is generally very difficult to modify because huge amounts
of organic material must be added. A typical loam soil is composed
15 of approximately 40 percent sand, 40 percent silt, and 20 percent
clay, making it an ideal garden soil. It is easily worked and retains
water and nutrients, which are slowly absorbed by plant roots.
A typical adobe soil is a clay soil present in hot, dry areas of the
20 country and often very hard and cracked. It has all the disadvantages
of a heavy clay soil and, being much drier, is more difficult to
correct.
1. What is the author's main purpose in the passage ?
2. According to the passage, the texture of sandy soil can be improved by mixing in
3. It can be inferred from the passage that the most distinguishing characteristic of adobe soil is
Xem lại bài Reading-Comprehension-Lesson 88 và bài Reading-Comprehension-Lesson 89
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