Page 259 - Environment: The Science Behind the Stories

Delineate the fundamentals of soil science, including • Farming techniques such as crop rotation, contour farm-
soil formation and soil properties ing, intercropping, terracing, shelterbelts, and conservation
tillage enable farmers to reduce soil erosion and boost crop
• Soil is a complex system and includes diverse biotic communities
that decompose organic matter. (p. 236) yields. (pp. 244–246)
• As a rule, vegetation helps anchor soil and prevent erosion.
• Weathering and biological activity help form soil, influ-
enced by climate, organisms, topography, parent material, (pp. 246–247)
and time. (pp. 236–237) • Overgrazing can cause soil degradation on grasslands and
diverse impacts to native ecosystems. (pp. 247, 250)
• Soil profiles consist of distinct horizons (such as the A Hori-
zon, or topsoil) with characteristic properties. (pp. 237–238) • Herd rotation, grazing limits, and research cooperation
with scientists are some pathways to sustainable grazing.
• Soil can be characterized by color, texture, structure, and
pH. (p. 238) (pp. 250, 252–253)
• Soil properties differ among regions and affect plant growth Describe techniques of watering and fertilizing crops,
and agriculture. (p. 239) and offer more sustainable alternatives

• We can conserve water by using efficient irrigation tech-
Analyze the causes and impacts of soil erosion and niques and choosing crops to match climates. (p. 251)
land degradation
• Overirrigation can cause salinization and waterlogging,
• As the human population grows and consumption increases, which lower crop yields and are difficult to mitigate. (pp.
pressures from agriculture are degrading Earth’s soil, and 252–253)
we lose 5–7 million ha (12–17 million acres) of productive
cropland annually. (p. 240) • Overapplying fertilizers can lead to pollution problems, as
leaching and runoff transport nutrients that affect ecosys-
• Soil degradation is the major component of land degrada- tems and human health. (pp. 253–254)
tion globally. (p. 240)
• Fertilizer use can be made more sustainable by targeting
• Some agricultural practices have resulted in severe erosion, fertilizers directly to plants and monitoring when they are
lowering crop yields. (p. 241) needed. (pp. 254–255)
• Desertification affects soils in the world’s arid regions.
(pp. 241–242) Summarize major policy approaches for pursuing soil
conservation and sustainable agriculture
• Some existing policies and subsidies worsen land degra-
Explain the principles of soil conservation and provide
solutions to soil erosion and land degradation dation. (pp. 255–256)
• Past agricultural policy has driven the destruction of wet-
• The Dust Bowl in the United States and similar events else-
where inspired scientists and farmers to develop ways to lands. (p. 256)
conserve topsoil. (pp. 242–243) • In the United States and across the world, governments are
devising agricultural policies and programs for conservation,
• Extension agents and agencies such as the National
Resources Conservation Service (NRCS) educate and assist such as the Conservation Reserve Program and other pro-
farmers. (pp. 243–244) grams funded in the periodic U.S. farm bills. (pp. 256–257)

Testing your Comprehension

1. Define the term soil profile. What are the influences on 4. How are soil horizons created? How is organic matter
the development of a soil profile, and how do profiles distributed in a typical soil profile?
differ? 5. Why is erosion generally considered a destructive pro-
2. Describe the methods used in traditional agriculture. cess? Name three human activities that can promote
How does industrial agriculture differ from traditional soil erosion. What factors affect the intensity of water
agriculture? erosion?
3. What processes are most responsible for the formation 6. What was the Dust Bowl? What impacts did it have on the
of soil? Describe the three types of weathering that con- United States? Describe innovations in soil conservation
tribute to soil formation. Name the five primary factors introduced by the Soil Conservation Service (SCS).
258 thought to influence soil formation.

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