Exam 20: Prospects for Global Soil Quality As Affected by Human Activities

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

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

Biofuel production form plant cellulose is likely to be a viable sustainable alternative to fossil fuel if all the entire above ground plant is harvested for conversion to fuel.

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

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.

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?

Slash-and-burn agriculture is primarily a system of water conservation and cycling.

Which of the following correctly describes human population issues pertinent to food production?

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

Increasing per hectare yields of crops will likely be a more significant source of increased food production in the next few decades than will expansion of land under cultivation.

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

During the 1990s,the rate of increase of food production has declined.

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

The distribution of different soil orders suggests all but one of the following:

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

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.

The proportion of the population of developing countries that are malnourished is higher today than it was 25 years ago.

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

More than 75% of the potentially arable land in South America is being cultivated.

Shifting cultivation is characterized by _____.