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Exam 14: Soil Erosion and Its Control

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Question 21

True/False

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In the United States, losses of soil due to wind and water erosion decreased by nearly 40% between 1982 and 2003.

A) True
B) False

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Question 22

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The R factor of the Universal soil-loss equation is concerned with _____.

A) soil erodibility
B) residue cover on the soil
C) terraces
D) climate
E) slope steepness

F) B) and C)
G) All of the above

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Question 23

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Conservation tillage systems are now in use on some 75% of the cropland in the USA.

To be classified as a conservation tillage practice, a system must leave at least what portion of the soil surface covered with plant residues?

If you want to maximize the quantity of vegetative cover on soil which of the following tillage practices would you use?

Wind erosion is generally not affected by _____.

You have been asked to produce continuous corn on five different soils using both no-till and conventional management systems. Yields on the no-till and conventional-till systems are about the same on all but one of the soils. In which of the following suborders would the poor- performing soil most likely be classified?

Although transportation of soil particles in suspension in the atmosphere is very spectacular, less than 40% of the wind erosion losses generally occur in this manner.

Conservation tillage has generally positive effects on soil physical properties.

Some 3/4 of the total soil loss from erosion in the United States is carried away by water.

Vegetative barriers planted on the contour have been found to create low-cost "natural" terraces.

The U.S. Department of Agriculture has developed soil-loss tolerance limits (T values) for different soils. Which of the following is the highest T value assigned for most soils in this country (Mg/ha) ?

The revised universal soil-loss equation (RUSLE) differs from USLE in all ways but one of the following.

Soils in Land Capability Class VIII areas are less subject to erosion than any other class.

The total global soil lost through erosion is generally greater from gully erosion than from sheet erosion.

In the U.S. Department of Agriculture's land capability classification systems, some 15% of the Nation's cultivated land is in Class I.

Saltation is the process of wind movement of salt-affected soils from one location to another in arid regions.

The soil erodibility factor in the Universal soil-loss equation (USLE) relates primarily to the soil's infiltration capacity and structural stability.

Compared to conventional tillage systems, most conservation tillage systems rely more heavily on herbicides to control weeds.

In one field trial comparing no-till and conventional tillage, soil samples taken after 15 years without liming revealed that the pH of the upper 15 cm was lower on the no-till plot than on the conventional plot. Which of the following most likely accounts for this difference?