Fertilizers partially restore plant nutrients lost by erosion, crop harvesting, and leaching. Farmers can use either organic fertilizer from plant and animal materials or commercial inorganic fertilizer produced from various minerals. Three basic types of organic fertilizer are animal manure, green manure, and compost. Animal manure includes the waste matter of cattle, horses, poultry, and other farm animals. It improves soil structure, adds organic nitrogen, and stimulates beneficial soil bacteria and fungi.
Despite its effectiveness, the use of animal manure in the United States has decreased. There are three reasons for this: the replacement of most mixed animal-raising and crop-farming operations with separate operations for growing crops and raising animals, the high costs of transporting animal manure from feedlots near urban areas to distant rural crop-growing areas, and the replacement of horses and other draft animals that added manure to the soil with tractors and other motorized farm machinery.
Green manure is fresh or growing green vegetation plowed into the soil to increase the organic matter and humus (degraded organic matter) available to the next crop. Compost is a sweet-smelling, dark-brown, humuslike material that is rich in organic matter and soil nutrients. It is produced when microorganisms in soil (mostly fungi and aerobic bacteria) break down organic matter such as leaves, food wastes, paper, and wood in the presence of oxygen. Compost is a rich natural fertilizer and soil conditioner that aerates soil, improves its ability to retain water and nutrients, helps prevent erosion, and prevents nutrients from being wasted by being dumped in landfills. Compost is produced by piling up alternating layers of nitrogen-rich wastes (such as grass clippings, weeds, animal manure, and vegetable kitchen scraps), carbon-rich plant wastes (dead leaves, hay, straw, sawdust), and topsoil. Compost provides a home for microorganisms that help decompose plant and manure layers and reduces the amount of plant wastes taken to landfills and incinerators.
Another form of organic fertilizer is the spores of mushrooms, puffballs, and truffles. Rapidly growing and spreading mycorrhizae fungi in the spores attach to plant roots and help them take in moisture and nutrients from the soil. Unlike typical fertilizers that must be applied every few weeks, one application of mushroom fungi lasts all year and costs just pennies per plant. The fungi also produce a bigger root system, which makes plants more disease resistant.
Corn, tobacco, and cotton can deplete the topsoil of nutrients, especially nitrogen, if planted on the same land several years in a row. One way to reduce such losses is crop rotation. Farmers plant areas or strips with nutrient-depleting crops one year. In the next year they plant the same areas with legumes, whose root nodules add nitrogen to the soil. In addition to helping restore soil nutrients, this method reduces erosion by keeping the soil covered with vegetation and helps reduce crop losses to insects by presenting them with a changing target.
Today, many farmers rely on commercial inorganic fertilizers containing nitrogen (as ammonium ions, nitrate ions, or urea), phosphorus (as phosphate ions), and potassium (as potassium ions). Inorganic commercial fertilizers are easily transported, stored, and applied. Worldwide, their use increased about tenfold between 1950 and 1989 but declined by 12% between 1990 and 1999. Today, the additional food they help produce feeds one of every three people in the world, without them, world food output, would drop an estimated 40%.
Commercial inorganic fertilizers have some disadvantages, however. These include (1) not adding humus to the soil, (2) reducing the soil’s content of organic matter and thus its ability to hold water (unless animal manure and green manure are also added to the soil), (3) lowering the oxygen content of soil and keeping fertilizer from being taken up as efficiently, (4) typically supplying only two or three of the twenty or so nutrients needed by plants, and (5) releasing nitrous oxide, a greenhouse gas that can enhance global warming. The widespread use of commercial inorganic fertilizers, especially on sloped land near streams and lakes, also causes water pollution as nitrate and phosphate fertilizer nutrients are washed into nearby bodies of water. The resulting plant nutrient enrichment causes algae blooms that use up oxygen dissolved in the water, thereby killing fish.
57. The word "beneficial" in the passage is closest in meaning to
58. According to paragraph 2, all of the following contributed to the decrease in the use of animal manure in the United States EXCEPT
A.changes in crop-farming and animal-raising operations
B. high transportation costs
C. the movement or large numbers of feedlots to distant rural areas
D. the introduction of motorized farm machinery
59. According to paragraph 3, what is one advantage of using compost in raising crops?
A.It makes the soil easier to plow in preparation for planting.
B. Water and nutrients stay in the soil and enable plant growth.
C. The damage to soil from microorganisms is reduced.
D. Excess oxygen is removed from the soil.
60. According to paragraph 3, one important physical effect of compost is that it
A.adds an oxygen-rich layer to the layers rich in nitrogen and carbon
B. decreases the quantity of plant material that needs to be discarded
C. helps keep the same amount of moisture in each layer of soil
D. reduces the amount of fungi and aerobic bacteria in the pile
61. According to paragraph 4, each of the following is an advantage of using mushroom spores as fertilizer EXCEPT:
A.The cost of using mushroom spores is relatively low.
B. A single application of mushroom spores is enough for a whole year.
C. Mushroom fungi are nutrients that plants can take in easily.
D. Mushroom fungi help protect plants from disease.
62. What is the ―target‖ referred to in the passage?
A.Crop losses that are caused by insects
B. The crop being grown at any given time
C. The areas that are planted with legumes
D. The various insects that cause crop losses
63. According to paragraph 5, one of the main reasons for using legumes in crop rotation is that legumes
A.have no serious insect pests
B. cover the soil more completely than any other crop does
C. build up the nitrogen content of the soil
D. are very easy to plant in strips
64. The word "rely" in the passage is closest in meaning to
D. waste money
65. According to paragraph 6, what is true about the quantities of commercial inorganic fertilizers used globally?
A.They are likely to drop by about 40% in the next ten years.
B. They have increased at a steady rate since 1950.
C. They increased during the 1990s, but at a slower rate than over the previous 40 years.
D. They dropped during the 1990s after having risen sharply over the previous 40 years.
66. How is paragraph 7 related to paragraph 6?
A.Paragraph 7 presents the drawbacks of a practice that paragraph 6 presents as an advantage.
B. Paragraph 7 argues that the viewpoint presented in paragraph 6 is based on several factual errors.
C. Paragraph 7 provides supporting evidence for some of the claims made in paragraph 6.
D. Paragraph 7 contrasts recently developed practices with the more traditional, established ones discussed in paragraph 6.
67. The phrase "twenty or so" in the passage is closest in meaning to
A.not quite twenty
B. roughly twenty
C. no more than twenty
D.a total of twenty
68. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
A The main cause of water pollution is the widespread use of commercial inorganic fertilizers on sloped land near streams and lakes.
B In addition, the widespread use of commercial inorganic fertilizers causes water pollution when nitrates and phosphates are washed into streams and lakes.
C。Also, the widespread commercial production of inorganic fertilizers has caused water pollution in bodies of water such as streams and lakes.
D。The most commonly used commercial inorganic fertilizers are nitrate and phosphate fertilizers, which cause water pollution if they enter streams or lakes.
Paragraph 1 Fertilizers partially restore plant nutrients lost by erosion, crop harvesting, and leaching. ■Farmers can use either organic fertilizer from plant and animal materials or commercial inorganic fertilizer produced from various minerals. ■ Three basic types of organic fertilizer are animal manure, green manure, and compost. ■ Animal manure includes the waste matter of cattle, horses, poultry, and other farm animals. ■ It improves soil structure, adds organic nitrogen, and stimulates beneficial soil bacteria and fungi.
69. Look at the four squares [■] that indicate where the following sentence can be added to the passage.
Thus, they help keep farmland productive over the long term.
Where would the sentence best fit?
70. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Drag your choices to the spaces where they belong. To review the passage, click on View Text.
Both organic and inorganic fertilizers are used to keep croplands productive. ● ● ●
1.Animal manures are effective organic fertilizers, but their use in the United States has decreased because of changes in modern farming.
2.Many economically important crops, including corn, tobacco, and cotton, can only be grown in the same fields year after year if large amounts of inorganic fertilizers are added to the soil.
3.Since 1950, farmers worldwide have begun to replace organic fertilizers with inorganic commercial ones, because the latter helps soil to retain oxygen.
4.Compost, a humuslike material that is rich in organic material, is often used together with green manure, since the combination of the two helps to prevent soil erosion.
5.Green manures, compost, mushroom spores, and crop rotation, if used correctly, all have positive impacts on growing conditions for crops that go beyond simply providing nutrients.
6.Commercial inorganic fertilizers play a key role in feeding the world’s population, but they can also cause serious environmental damage.
托福真题答案BCBBC BCBDA BBA 156