loss of soil

growing crops

The photos in Figure 19.2 show how farming practices can increase soil erosion. Plant roots penetrate the soil and keep it from eroding. Plowing turns over bare soil and cuts through plant roots. Bare soil is exposed to wind and water. In the past, farmers always plowed fields before planting. Some farmers now use no-till farming, which does not disturb the soil as much. The problem doesnt stop with plowing. Crops are usually planted in rows, with bare soil in between the rows. In places where crops grow only during part of the year, the land may be bare for a few months.

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human actions and soil erosion

Runoff carved channels in the soil in Figure 19.1. Running water causes most soil erosion, but wind can carry soil away too. What humans do to soil makes it more or less likely to be eroded by wind or water. Human actions that can increase soil erosion are described below.

logging mining and construction

Other human actions that put soil at risk include logging, mining, and construction. You can see examples of each in Figure 19.4. When forests are cut down, the soil is suddenly exposed to wind and rain. Without trees, there is no leaf litter to cover the ground and protect the soil. When leaf litter decays, it adds humus and nutrients to the soil. Mining and construction strip soil off the ground and leave the land bare. Paved roads and parking lots prevent rainwater from soaking into the ground. This increases runoff and the potential for soil erosion.

grazing animals

As you can see in Figure 19.3, some grazing animals, especially sheep and goats, eat grass right down to the roots. They may even pull the grass entirely out of the ground. Grazing animals can kill the grass or thin it out so much that it offers little protection to the soil. If animals are kept in the same place too long, the soil may become completely bare. The bare soil is easily eroded by wind and water.

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preventing soil erosion

Soil is a renewable resource, but it can take thousands of years to form. Thats why people need to do what they can to prevent soil erosion.

recreation

Even things that people do for fun can expose soil to erosion. For example, overuse of hiking trails can leave bare patches of soil. Off-road vehicles cause even more damage. You can see examples of this in Figure 19.5.

farming methods that reduce soil erosion

The Dust Bowl taught people that soil could be lost by plowing and growing crops. This led to the development of new ways of farming that help protect the soil. Some of the methods are described in Figure 19.6.

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other ways to reduce soil erosion

There are several other ways to help prevent soil loss. Some of them are shown in Figure 19.7. Prevent overgrazing. Frequently move animals from field to field. This gives the grass a chance to recover. Avoid logging steep hillsides. Cut only a few trees in any given place. Plant new trees to replace those that are cut down. Reclaim mine lands. Save the stripped topsoil and return it to the land. Once the soil is in place, plant trees and other plants to protect the bare soil. Use barriers to prevent runoff and soil erosion at construction sites. Plant grass to hold the soil in place. Develop paving materials that absorb water and reduce runoff. Restrict the use of off-road vehicles, especially in hilly areas.

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instructional diagrams

No diagram descriptions associated with this lesson

questions

Some of the soil from the Dust Bowl ended up in the Atlantic Ocean.

-->  a. true

b. false

Most land organisms could not survive without soil.

-->  a. true

b. false

Plants cause soil loss by using up soil nutrients.

a. true

-->  b. false

Soil that is lost can never be replaced.

a. true

-->  b. false

Large areas of pavement help prevent soil erosion.

a. true

-->  b. false

Hiking is a form of recreation that does not increase soil erosion.

a. true

-->  b. false

Frequently moving grazing animals from field to field increases soil loss.

a. true

-->  b. false

Grasses are good groundcover plants for holding soil in place.

-->  a. true

b. false

Topsoil stripped from a mining site can be saved and reused.

-->  a. true

b. false

Barriers that reduce runoff can help prevent soil erosion at construction sites.

-->  a. true

b. false

plants that hold soil in place between growing seasons

a. contour cropping

b. strip cropping

-->  c. cover crop

d. windbreak

e. no-till planting

f. plowing

g. terracing

planting fields without plowing them first

a. contour cropping

b. strip cropping

c. cover crop

d. windbreak

-->  e. no-till planting

f. plowing

g. terracing

row of trees planted between fields

a. contour cropping

b. strip cropping

c. cover crop

-->  d. windbreak

e. no-till planting

f. plowing

g. terracing

building broad steps on steep slopes before planting

a. contour cropping

b. strip cropping

c. cover crop

d. windbreak

e. no-till planting

f. plowing

-->  g. terracing

planting crops in curved rows to follow the contour of hills

-->  a. contour cropping

b. strip cropping

c. cover crop

d. windbreak

e. no-till planting

f. plowing

g. terracing

cutting through plant roots and turning over soil before planting

a. contour cropping

b. strip cropping

c. cover crop

d. windbreak

e. no-till planting

-->  f. plowing

g. terracing

planting strips of groundcover plants between fields of crops

a. contour cropping

-->  b. strip cropping

c. cover crop

d. windbreak

e. no-till planting

f. plowing

g. terracing

Factors that contributed to the Dust Bowl included

a. plowing the land.

b. lack of rain.

c. high winds.

-->  d. all of the above

Plants need soil to

a. obtain carbon dioxide.

-->  b. anchor their roots.

c. prevent runoff.

d. all of the above

The main cause of soil erosion is

a. wind.

b. abrasion.

c. ice wedging.

-->  d. running water.

Farming practices that increase soil erosion include

-->  a. tilling

b. strip cropping

c. contour cropping

d. two of the above

Grazing animals that are likely to leave the soil bare include

a. cattle.

b. sheep.

c. goats.

-->  d. two of the above

Human actions that increase the risk of soil loss include

-->  a. logging.

b. terracing.

c. tree planting.

d. no till planting.

Soil erosion can be reduced by

a. paving the land.

-->  b. planting cover crops.

c. planting crops in rows.

d. riding off-road vehicles in hilly areas.

diagram questions

No diagram questions associated with this lesson