Exam 20: Prospects for Global Soil Quality

Alley cropping systems help control soil erosion, but crop yields are usually constrained by competition for water and nutrients between the crop plants and the border woody plants.

Alfisols are of greater importance in semi-arid tropics than in the humid tropics.

Significant amounts of nitrates are adsorbed in some Oxisols by clay layers below the depths that most crop root systems can reach.

Food production increases of the past 30 years have been attributed to either increases in areas of land under cultivation or increases in yields per hectare.In which region has the proportion of increased food supply attributed to increased areas under cultivation been the highest?

Which of the following has NOT been an effect of the intensified agriculture of the past 40 years?

There are more hungry people on Earth today than at any time in history

Which of the following is NOT a likely component of the ecology-based paradigm for future intensified U.S.food production?

Which of the following describes world food production trends?

Which if the following is true about a soil quality index (SQI)?

Which of the following is not a characteristic of alley cropping systems that are being studied as one alternative to slash-and-burn systems?

Many soil quality functions must be measured to define a soil quality indicator property.

The quality of a soil is most directly related to___.

In which region of the world does overall crop removal of nutrients significantly exceed the return of these nutrients in crop residues and chemical fertilizers?

Shifting cultivation is characterized by _____.

Africa lags far behind other developing areas in the use of chemical fertilizers.

Representative shifting cultivation systems today permit more soil degradation than those in use 30 years ago because the period of fallow has been decreased.

In the past 25 years, population pressures have forced more land to come under shifting cultivation, but per hectare yields from the system have declined.

Poor people today pay a greater proportion of their incomes for cereal foods (wheat, rice, corn) than they did just 30 years ago.

Conservation tillage systems can decrease soil erosion and runoff and increase water infiltration in soils of the tropics.

Global warming will likely be curtailed if the land area used for agriculture in South America is greatly increased.