This productivity, however, has its price. Intensive cultivation exposes the earth to the damaging forces of nature. Every year wind and water remove tons of rich soil from the nations croplands.
Each field is covered by a limited amount of topsoil, the upper layer of earth which is richest in the nutrients and minerals necessary for growing crops. Ever since the first farmers arrived in the Midwest almost 200 years ago,cultivation and, consequently, erosion have been decreasing the supply of topsoil. In the 1830s, nearly two feet of rich, black top soil covered the Midwest. Today the average depth is only eight inches, and every decade another inch is blown or washed away. This erosion is steadily decreasing the productivity of valuable cropland. A United States Agricultural Department survey states that if erosion continues at its present rate, corn and soybean yields in the Midwest may drop as much as 30 percent over the next 50 years.
So far, farmers have been able to compensate for the loss of fertile topsoil by applying more chemical fertilizers to their fields; however, while this practice has increased crop yields, it has been devastating for ecology. Agriculture has become one of the biggest polluters of the nations precious water supply. Rivers, lakes, and underground reserves of water are being filled in and poisoned by soil and chemicals carried by drainage from eroding fields. Furthermore, fertilizers only replenish the soils they do not prevent its loss.
26. The last sentence in the first paragraph gives an example to show_______.
A. that American farmers manage to feed the total population of the U. S.
B. the leading position of the U. S. farming in the world
C. how important American people consider their farming
D. that many people in the world rely on the export of the agricultural products of the U. S. A.
27. In order to compensate for the loss of fertile topsoil, farmers have been_______.
A. planting less corn and soybean B. putting fertilizers on their fields
C. preventing soil erosion D. decreasing the supply of top soil
28. At the present rate, approximately how many years later the black top soil now covering the Midwest will completely be blown or washed away?
A. 120 years later. . B. 80 years later.
C. 50 years later. D. 100 years later.
29. This practice in Paragraph 4 refers to_______.
A. that farmers have lowered the yield of corn and soybean
B. that farmers have expanded croplands
C. that farmers have applied more chemical fertilizers
D. that the top soil has been decreased greatly
30. All of the following are statements about the disadvantages of fertilizers EXCEPT that
A. they replenish the soil B. they do not prevent the loss of soil
C. they are destroying the ecology D. they pollute the nations water supply
26. D 27. B 28. B 29. C 30. A
上一篇: 六级冲刺练习:阅读(144)
下一篇: 六级冲刺练习:阅读(136)
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1-3动词形式填空(二)
江苏省姜堰市张甸中学高三英语牛津译林版一轮复习:Module1 Unit2《Growing pains》定语从句 课件1
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修8《Unit 4 Films and film events》复习学案
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修9《Unit 2 Witnessing time》基础过关作业四
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1 《School life》巩固练习
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修9《Unit 2 Witnessing time》单词复习
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1-2基础训练
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修9《Unit 4 Behind beliefs》基础过关作业三
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1-3各单元默写过关
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修10《Unit 4 Law and order》学案三
江苏省姜堰市张甸中学高三英语一轮复习基础过关作业:M5U2《The Environment》短语
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修9《Unit 3 The meaning of colour》基础过关作业一
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit3《Looking good,feeling good》复习学案1
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修8《Unit 3 The world of colours and light》复习学案一
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1 《School life》随堂练习
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1-3笔记整理
江苏省姜堰市张甸中学高三英语一轮复习基础过关作业:M5U2《The Environment》课文原句
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修8《Unit 2 The universal language》教学案
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修10《Unit 4 Law and order》学案一
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修9《Unit 4 Behind beliefs》周末作业二
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修10《Unit 3 Protecting ourselves》学案五
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修10《Unit 3 Protecting ourselves》学案十
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1-3默写过关
江苏省姜堰市张甸中学高三英语牛津译林版一轮复习:Module1 Unit2《Growing pains》定语从句 课件3
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修9《Unit 3 The meaning of colour》基础过关作业二
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修10《Unit 1 Building the future》基础过关作业三
江苏省姜堰市张甸中学2012届高三英语一轮复习牛津译林版模块选修10《Unit 3 Protecting ourselves》学案四
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修10《Unit 1 Building the future》基础过关作业二
江苏省姜堰市张甸中学2017届高三英语一轮复习牛津译林版模块选修9《Unit 3 The meaning of colour》基础过关作业三
江苏省姜堰市张甸中学高三英语一轮复习:Module1 Unit1-3单词过关检测