Page 260 - Environment: The Science Behind the Stories

7. What farming techniques help reduce the risk of erosion? 9. How can irrigation practices be made more sustainable?
Explain how no-till farming works. Why does this method How do fertilizers boost crop growth? How does excess
reduce soil erosion? fertilizer added to soil sometimes end up in water sup-
8. Describe the effects of overgrazing on soil. What policies plies and in the atmosphere?
can be linked to the practice of overgrazing? What condi- 10. Briefly describe the successes of the Malpai Borderlands
tions characterize sustainable grazing practices? restoration project.

Seeking Solutions

1. How do you think a farmer can best help to conserve soil? grasslands that have been degraded by decades of over-
How do you think a scientist can best help to conserve grazing. Soil is eroding, creating large gullies. Invasive
soil? How do you think a national government can best weeds are replacing native grasses. Shrubs are encroach-
help to conserve soil? ing on grassland areas because fire was suppressed.
2. How and why might actual soils differ from the ideal- Environmentalists want an end to ranching on the land.
ized six-horizon soil profile presented in the chapter? Ranchers want grazing to continue. What steps would
How might departures from the idealized profile indi- you take to assess the land’s condition and begin restor-
cate the impact of human activities? Provide at least ing its soil and vegetation? Would you allow grazing, and
three examples. if so, would you set limits on it?
3. Discuss how the methods of no-till farming or conserva- 6. THINK IT THRoUGH You are the head of an international
tion tillage, as described in this chapter, can enhance soil granting agency that assists farmers with soil conser-
quality. What other benefits can these approaches have? vation and sustainable agriculture. You have $10 mil-
What drawbacks or negative effects might no-till or con- lion to disburse. Your agency’s staff has decided that
servation tillage practices have on soil and water quality, the funding should go to (1) farmers in an arid area
and how might these be minimized? of Africa prone to salinization, (2) farmers in a fast-
growing area of Indonesia where swidden agriculture
4. Aside from no-till farming, select two other methods or is practiced, (3) farmers in Argentina practicing no-till
approaches described in this chapter that you feel are pro- agriculture, and (4) farmers in a dryland area of Mon-
moting the science or practice of soil conservation, and golia undergoing desertification. What types of pro-
describe how they are accomplishing this.
jects would you recommend funding in each of these
5. THINK IT THRoUGH You are a land manager with the areas, how would you apportion your funding among
U.S. Bureau of Land Management (BLM, p. 256) and them, and why?
have just been put in charge of 500,000 acres of public

Calculating ecological Footprints

In the United States, approximately 5 tons of topsoil are lost material or its derived products (sugar, for example) per day.
for every ton of grain harvested. Erosion rates vary greatly In the first two columns of the table, calculate the annual
with soil type, topography, tillage method, and crop type. topsoil losses associated with growing this food for you and
For simplicity, let us assume that the 5:1 ratio applies to all for other groups, assuming the same diet. CHAPTER 9 • So I l AN d A gr I culT ure
plant crops and that a typical diet includes 1 pound of plant

Plant products Soil loss at 5:1 Soil loss at 3.25:1 Reduced soil loss at 3.25:1
consumed (lb) ratio (lb) ratio (lb) relative to 5:1 ratio (lb)
You 365 1825 1186 639
Your class
Your state
United States 259

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