chapter 14 food soil resources l.
Skip this Video
Loading SlideShow in 5 Seconds..
Chapter 14: Food & Soil Resources PowerPoint Presentation
Download Presentation
Chapter 14: Food & Soil Resources

Loading in 2 Seconds...

play fullscreen
1 / 98

Chapter 14: Food & Soil Resources - PowerPoint PPT Presentation

  • Uploaded on

Chapter 14: Food & Soil Resources. T he three systems humans depend on for their food supply Croplands (77%) – land used for planting crops; vegetables, fruits, and grains Rangelands (16%)- Land used for grazing livestock; meat products

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Chapter 14: Food & Soil Resources' - jaden

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
The three systems humans depend on for their food supply

Croplands (77%) – land used for planting crops; vegetables, fruits, and grains

Rangelands (16%)- Land used for grazing livestock; meat products

Ocean fisheries (7%) - shellfish/fish (6% of protein in human diet)



Food Supply




Major increase in food production post-1950

High-TechGear &Electronics

FeedlotsFeed Pens


Farm Equip.











human population growth and food production
Human Population Growth and Food Production

9 billion humans by 2054

More food than has been produced in last 10k yrs

Is current technology capable?

Environmental degradation?


Water supply (irrigation)



Ecological services (matter; energy)

lack of diversity in food
Lack of Diversity in Food

30,000 edible

plant species

3 grain crops that provide “more than ½ of the calories people consume”.

But 90% of all food only comes from

15 plants [esp. wheat, rice, corn] and

8 animals- [esp. beef, pork, chicken]


1% energy

6 % protein

major types of agriculture
Major Types of Agriculture

Traditional subsistence (20%, 44% pop.)

Low-input, human labor, "just enough"

Shifting cultivation; nomadic livestock

Traditional intensive

Higher input, "more than enough"


Monoculture cash crops (bananas, coffee, sugarcane, etc)

Industrialized (high-input)

25% of all cropland, developed nations


Plantation agriculture

Industrialized agriculture

Nomadic herding

Shifting cultivation

Intensive traditional agriculture

No agriculture

Fig. 12.2, p. 263

the green revolution
The Green Revolution

increased production of food per unit of area of cropland; planting monocultures, increase use of pesticides, water, fertilizers, etc.

Since 1950

  • Develop & plant monocultures (ie. corn)
  • Input fertilizer, pesticides, water
  • Multiple cropping on plot of land

Since 1967

  • Fast growing dwarf varieties of rice and wheat
  • More food on less land
  • Increase use of fossil fuels, fertilizers, pesticides, irrigation

Age of Genetic Engineering

  • >2/3 of products on U.S. grocery store shelves contain ingredients from GE crops!
green revolution increasing global food production
Green-Revolution- increasing global food production…

selective breeding

genetic engineering (GMO’s)

high energy input (8% world oil)

fertilizers, pesticides, water

dwarf varieties- 3-5x yield

multicropping (2-3/year)




Farm more land =

Increase crop yield / land area



High Input

High intensity

frequency of



Intensified agriculture meant monocultures, vast spreads of a single crop.

This is economically efficient, but increases risk of catastrophic failure (“all eggs in one basket”).

Wheat monoculture in Washington

Figure 9.4a

green revolution environmental impacts
Green revolution: Environmental impacts

Intensification of agriculture causes environmental harm:

Pollution from synthetic fertilizers

Pollution from synthetic pesticides

Water depleted for irrigation

Fossil fuels used for heavy equipment

However, without the green revolution, much more land would have been converted for agriculture, destroying forests, wetlands, and other ecosystems.


Second green revolution

(developing countries)

First green revolution

(developed countries)

Major International agricultural

research centers and seed banks

energy use in food production industrial agriculture united states
Energy Use in Food Production:Industrial Agriculture(United States)

Since1940’s: 2x production on the same amount of land

Agribusiness- big companies and large family farms own 75% of US food production

- 2% pop.= farmers; 9% pop.= involve in production

- Agriculture provides18% US GNP; 19% jobs (private sect); 0.3% world's labor

- 17% of world’s grain is produced in the US; ½ the world’s corn & soybean exports

  • Putting food on the table utilizes 17% of US commercial energy, mostly from oil
  • Food production uses 3 units of fossil fuel energy for 1 unit of food energy obtained. Units of energy take in to account the energy used to grow, store, process, pack, process, refrigerate, and cook
      • Plants involve > energy out than in; Livestock involve > energy in, than out.
energy use in food production traditional and traditional intensive
Energy Use in Food Production: Traditional and Traditional Intensive
  • 20% of world food on 75% cultivated land
  • Most traditional farmers use INTERPLANTING - growing several crops on a single plot of land.

Types of interplanting-

  • Polyvarietals - varieties of 1 crop
  • Intercropping - 2+ different on same plot (legumes/grain)
  • Agroforestry/alley cropping - crops/trees together
  • Polyculture - many plants maturing at different times on same plot

Advantages include: < energy input, erosion/weather protection, pest/herbicides not needed






soil erosion and degradation
Soil Erosion and Degradation

Causes: water, wind, and people

  • Land degradation- when natural or human induced processes reduce the future ability of land to support crops, livestock or wild species. (i.e. soil erosion due to flowing water or wind)
  • Erosion of topsoil leads to loss of soil fertility and increase sediment in nearby surface waters which can block sunlight, kill fish, and clog irrigation ditches, channels, etc.
causes of soil degradation
Causes of soil degradation

Most soil degradation is caused by:

• livestock overgrazing

• deforestation

• cropland agriculture

Figure 8.2

types of soil erosion
Types of soil erosion

Splash erosion


Gully erosion

Sheet erosion

Figure 8.11


A loss of more than 10% productivity due to:

• Erosion

• Soil compaction

• Forest removal

• Overgrazing

• Drought

• Salinization

• Climate change

• Depletion of water resources

When severe, there is expansion of desert areas, or creation of new ones, e.g., the Middle East, formerly, “Fertile Crescent”.

the dust bowl
The Dust Bowl

Drought and degraded farmland produced the 1930s Dust Bowl.

Storms brought dust from the U.S. Great Plains all the way to New York and Washington, and wrecked many lives.

Figure 8.14








Soil compaction

Natural climate


Worsening drought


Economic losses

Lower living




preventing soil degradation
Preventing soil degradation

Several farming strategies to prevent soil degradation:

• Crop rotation

• Contour farming

• Intercropping

• Terracing

• Shelterbelts

• Conservation tillage

soil conservation
Soil conservation

As a result of the Dust Bowl, the U.S. Soil Conservation Act of 1935 and the Soil Conservation Service (SCS) were created.

SCS:Local agents in conservation districtsworked with farmers to disseminate scientific knowledge and help them conserve their soil.

crop rotation
Crop rotation

Alternating the crop planted (e.g., between corn and soybeans) can restore nutrients to soil and fight pests and disease.

Figure 8.16a

contour farming
Contour farming

Planting along contour lines of slopes helps reduce erosion on hillsides.

Figure 8.16b


Mixing crops such as in strip cropping can provide nutrients and reduce erosion.

Figure 8.16c


Cutting stairsteps or terraces is the only way to farm extremely steep hillsides without causing massive erosion. It is labor-intensive to create, but has been a mainstay for centuries in the Himalayas and the Andes.


Rows of fast-growing trees around crop plantings provide windbreaks, reducing erosion by wind.

Figure 8.16e

conservation tillage
Conservation tillage

Conservation tillage is not a solution for all crops everywhere.

  • It often requires more chemical herbicides (because weeds are not plowed under).
  • It often requires more fertilizer (because other plants compete with crops for nutrients).

No-till and reduced-tillage farming leaves old crop residue on the ground instead of plowing it into soil. This covers the soil, keeping it in place.

Here, corn grows up out of a “cover crop.”

But legume cover crops can keep weeds at bay while nourishing soil, and green manures can be used as organic fertilizers.

Figure 8.16f



Conservation Tillage



Can increase

herbicide use for

some crops

Leaves stalks that

can harbor crop

pests and fungal

diseases and

increase pesticide




in expensive


Reduces erosion

Saves fuel

Cuts costs

Holds more soil


Reduces soil


Allows several crops

per season

Does not reduce

crop yields

Reduces CO2

release from soil

central case no till agriculture in brazil
Central Case: No-Till Agriculture in Brazil

Southern Brazil’s farmers were suffering falling yields, erosion, and pollution from agrichemicals.

They turned to no-till farming, which bypasses plowing.

Erosion was reduced, soils were enhanced, and yields rose greatly. No-till methods are spreading worldwide.


The artificial provision of water to support agriculture

70% of all freshwater used by humans is used for irrigation.

Irrigated land globally covers more area than all of Mexico and Central America combined.

Irrigation has boosted productivity in many places … but too much can cause problems.

waterlogging and salinization
Waterlogging and salinization

Overirrigation can raise the water table high enough to suffocate plant roots with waterlogging.

Salinization(buildup of salts in surface soil layers) is a more widespread problem. Salt in soils decreases the osmotic potential of the soil so that plants can't take up water from it. The salts can also be directly toxic, but plant troubles usually result primarily from inability to take up water from salty soils

Evaporation in arid areas draws water up through the soil, bringing salts with it. Irrigation causes repeated evaporation, bringing more salts up.



Soil Salinization



Flushing soil

(expensive and

wastes water)

Not growing crops

for 2-5 years

Installing under-

ground drainage

systems (expensive)

Reduce irrigation

Switch to salt-

tolerant crops

(such as barley,

cotton, sugar beet)

global fertilizer usages
Global fertilizer usages

Fertilizer use has risen dramatically in the past 50 years.

Figure 8.19b



Inorganic Commercial Fertilizers



Easy to transport

Easy to store

Easy to apply

Inexpensive to produce

Help feed one of every

three people in the


Without commercial

inorganic fertilizers,

world food output could

drop by 40%

Do not add humus to soil

Reduce organic matter

in soil

Reduce ability of soil to

hold water

Lower oxygen content of


Require large amounts of

energy to produce,

transport, and apply

Release the greenhouse

gas nitrous oxide (N2O)

Runoff can overfertilize

nearby lakes and kill fish


When livestock eat too much plant cover on rangelands, impeding plant regrowth.

The contrast between ungrazed and overgrazed land on either side of a fenceline can be striking.

Figure 8.22


Overgrazing can set in motion a series of positive feedback loops.

Figure 8.21

global food production
Global food production

World agricultural production has risen faster than human population.

Figure 9.1

global food security
Global food security

However, the world still has 800 million hungry people, largely due to inadequate distribution.

Considering soil degradation, can we count on food production continuing to rise?

Global food security is a goal of scientists and policymakers worldwide.


Undernourishment =

too few calories (especially developing countries)


too many calories (especially developed world)

Malnutrition = lack of nutritional requirements

(causes numerous diseases, esp. in developing world)

Figure 9.2

food production nutrition and environmental effects
Food Production, Nutrition and Environmental Effects

~ 1 in 6 people in developing nations are chronically undernourished or malnourished

Common nutritional deficiency diseases:

Marasmus and Kwashiorkor

M = diet low in calories and protein

K = severe protein deficiency




to disease

High death

rate for






to learn



to work






Feedback loop

Fig. 12.9, p. 269


Environmental effects of food production

Biodiversity Loss


Loss and degradation of habitat from

clearing grasslands and forests and

draining wetland

Fish kills from pesticide runoff

Killing of wild predators to protect


Loss of genetic diversity from

replacing thousands of wild crop

strains with a few monoculture strains


Loss of fertility





Air Pollution


Water waste

Aquifer depletion

Increased runoff and

flooding from land cleared

to grow crops

Sediment pollution from


Fish kills from pesticide


Greenhouse gas emissions from fossil

Fuel issue

Other air pollutants from fossil fuel use

Pollution from pesticide sprays

Surface and groundwater

pollution from pesticides

and fertilizers

Overfertilization of lakes

and slow-moving rivers

from runoff of nitrates

and phosphates from

fertilizers, livestock

wastes, and food

processing wastes


Human Health

Nitrates in drinking water

Pesticide residues in drinking water,

food, and air

Contamination of drinking and

swimming water with disease

organisms from livestock wastes

Bacterial contamination of meat

pesticide use
Pesticide use

Pesticide use is still rising sharply across the world, although growth has slowed in the U.S.

1 billion kg (2 billion lbs.) of pesticides are applied each year in the U.S.

Figure 9.5

biological control
Biological control

Synthetic chemicals can pollute and be health hazards.

Biological control (biocontrol) avoids this.

Biocontol entails battling pests and weeds with other organisms that are natural enemies of those pests and weeds.

(“The enemy of my enemy is my friend.”)

biological control51
Biological control

Biocontrol has had success stories.

Bacillus thuringiensis (Bt) = soil bacterium that kills many insects. In many cases, seemingly safe and effective.

Cactus moth, Cactoblastis cactorum (above), was used to wipe out invasive prickly pear cactus in Australia.

Figure 9.7

but biocontrol is risky
But biocontrol is risky

Most biocontrol agents are introduced from elsewhere.

Some may turn invasive and become pests themselves!

Cactus moths brought to the Caribbean jumped to Florida, are eating native cacti, and spreading.

Wasps and flies brought to Hawaii to control crop pests are parasitizing native caterpillars in wilderness areas.

integrated pest management ipm
Integrated pest management (IPM)

Combines biocontrol, chemical, and other methods

May involve:

• Biocontrol

• Pesticides

• Close population monitoring

• Habitat modification

• Crop rotation

• Transgenic crops

• Alternative tillage

• Mechanical pest removal

genetic modification of food
Genetic modification of food

Manipulating and engineering genetic material in the lab may represent the best hope for increasing agricultural production further without destroying more natural lands.

But many people remain uneasy about genetically engineering crop plants and other organisms.

some gm foods
Some GM foods

Golden rice: Enriched with vitamin A.

But too much hype?

FlavrSavr tomato: Better taste?

But pulled from market.

Ice-minus strawberries: Frost-resistant bacteria sprayed on.

Images alarmed public.

Bt crops: Widely used on U.S. crops.

But ecological concerns?

Figure 9.12

scientific concerns about gm organisms
Scientific concerns about GM organisms

Are there health risks for people?

Can transgenes escape into wild plants, pollute ecosystems, harm organisms?

Can pests evolve resistance to GM crops just as they can to pesticides?

Can transgenes jump from crops to weeds and make them into “superweeds”?

Can transgenes get into traditional native crop races and ruin their integrity?

socioeconomic and political concerns about gm products
Socioeconomic and political concerns about GM products

Should scientists and corporations be “tinkering with” our food supply?

Are biotech corporations testing their products adequately, and is outside oversight adequate?

Should large multinational corporations exercise power over global agriculture and small farmers?

europe vs america
Europe vs. America

Europe:has followed precautionary principle in approach to GM foods. Governments have listened to popular opposition among their citizens.

U.S.:GM foods were introduced and accepted with relatively little public debate.

Relations over agricultural trade have been uneasy, and it remains to be seen whether Europe will accept more GM foods from the U.S.



Genetically Modified Food and Crops





Need less fertilizer

Need less water

More resistant to insects,

plant disease, frost, and


Faster growth

Can grow in slightly salty


Less spoilage

Better flavor

Less use of conventional


Tolerate higher levels of

pesticide use

Higher yields

Irreversible and

unpredictable genetic

and ecological effects

Harmful toxins in food

From possible plant cell


New allergens in food

Lower nutrition

Increased evolution of


Insects and plant


Creation of herbicide-

Resistant weeds

Harm beneficial insects

Lower genetic diversity

preserving crop diversity
Preserving crop diversity

Native cultivars of crops are important to preserve, in case we need their genes to overcome future pests or pathogens.

Diversity of cultivars has been rapidly disappearing from all crops throughout the world.

seed banks preserve seeds crop varieties
Seed banks preserve seeds, crop varieties

Seed banks are living museums of crop diversity, saving collections of seeds and growing them into plants every few years to renew the collection.

Careful hand pollination helps ensure plants of one type do not interbreed with plants of another.

Figure 9.14

animal agriculture livestock and poultry
Animal agriculture: Livestock and poultry

Consumption of meat has risen faster than population over the past several decades.

Figure 9.15

feedlot agriculture
Feedlot agriculture

Increased meat consumption has led to animals being raised in feedlots (factory farms), huge pens that deliver energy-rich food to animals housed at extremely high densities.

Figure 9.16

feed lots
Feed lots
  • More production of livestock in smaller, condensed spaces; Produce more using less space and energy
  • Increases need for antibiotics due to enclosed spaces; leads to issues of cruelty to animals
  • Hormones given to produce larger animals for more meat= more $!
feedlot agriculture environmental impacts
Feedlot agriculture: Environmental impacts

Immense amount of waste produced, polluting air and water nearby

Intense usage of chemicals (antibiotics, steroids, hormones), some of which persist in environment

However, if all these animals were grazing on rangeland, how much more natural land would be converted for agriculture?

food choices energy choices
Food choices = energy choices

Energy is lost at each trophic level.

When we eat meat from a cow fed on grain, most of the grain’s energy has already been spent on the cow’s metabolism.

Eating meat is therefore very energy inefficient. - Hence, the “Eating Green” Challenge! Feb. 28- March 7

grain feed input for animal output
Grain feed input for animal output

Some animal food products can be produced with less input of grain feed than others.

Figure 9.17

land and water input for animal output
Land and water input for animal output

Some animal food products can be produced with less input of land and water than others.

Figure 9.18


The raising of aquatic organisms for food in controlled environments

Provides 1/3 of world’s fish for consumption

220 species being farmed

The fastest growing type of food production

benefits of aquaculture
Benefits of aquaculture

Provides reliable protein source for people, increases food security

Can be small-scale, local, and sustainable

Reduces fishing pressure on wild stocks, and eliminates bycatch

Uses fewer fossil fuels than fishing

Can be very energy efficient

environmental impacts of aquaculture
Environmental impacts of aquaculture

Density of animals leads to disease, antibiotic use, risks to food security.

It can generate large amounts of waste.

Often animals are fed grain, which is not energy efficient.

Sometimes animals are fed fish meal from wild-caught fish.

Farmed animals may escape into the wild and interbreed with, compete with, or spread disease to wild animals.

catching and raising more fish
Catching and Raising More Fish
  • Fisheries
  • Fishing methods (See Fig. 14-24 p. 299)
  • Sustainable yield
  • Overfishing- decreased biodiversity; affects aquatic food chains; bycatch; loss of food
  • Commercial extinction
  • Aquaculture- collectively involves fish farming and ranching;
  • salmon and shrimp
environmental impacts of aquaculture74
Environmental impacts of aquaculture

Transgenic salmon (top) can compete with or spread disease to wild salmon (bottom) when they escape from fish farms.

Figure 9.20



3 methods used to catch fish:

trawl bag

drift net







Highly efficient

High yield in small

volume of water

Increased yields

through cross-

breeding and genetic


Can reduce over-

harvesting of

conventional fisheries

Little use of fuel

Profit not tied to price

of oil

High profits

Large inputs of land, feed,

And water needed

Produces large and

concentrated outputs of


Destroys mangrove forests

Increased grain production

needed to feed some


Fish can be killed by

pesticide runoff from

nearby cropland

Dense populations

vulnerable to disease

Tanks too contaminated to

use after about 5 years



More Sustainable Aquaculture

  • Reduce use of fishmeal as a feed to reduce depletion of other fish
  • Improve pollution management of aquaculture wastes
  • Reduce escape of aquaculture species into the wild
  • Restrict location of fish farms to reduce loss of mangrove forests and other threatened areas
  • Farm some aquaculture species (such as salmon and cobia) in deeply submerged cages to protect them from wave action and predators and allow dilution of wastes into the ocean
  • Set up a system for certifying sustainable forms of aquaculture
sustainable agriculture
Sustainable agriculture

Agriculture that can practiced the same way far into the future

Does not deplete soils faster than they form

Does not reduce healthy soil, clean water, and genetic diversity essential for long-term crop and livestock production

Low-input agriculture= small amounts of pesticides, fertilizers, water, growth hormones, fossil fuel energy, etc.

Organic agriculture= no synthetic chemicals used. Instead, biocontrol, composting, etc.

organic farming
Organic farming

Small percent of market, but is growing fast

1% of U.S. market, but growing 20%/yr

3–5% of European market, but growing 30%/yr

Organic produce:

Advantages for consumers: healthier; environmentally better

Disadvantages for consumers: less uniform and appealing-looking; more expensive

conclusions challenges
Conclusions: Challenges

Chemical pesticides pollute, and kill pollinators, and pests evolve resistance.

GM crops show promise for social and environmental benefits, but questions linger about their impacts.

Much of the world’s crop diversity has vanished.

Feedlot agriculture and aquaculture pose benefits and harm for the environment and human health.

conclusions challenges81
Conclusions: Challenges

Organic farming remains a small portion of agriculture.

Human population continues to grow, requiring more food production.

Soil erosion is a problem worldwide.

Salinization, waterlogging, and other soil degradation problems are leading to desertification.

Grazing and logging, as well as cropland agriculture, contribute to soil degradation.

conclusions solutions
Conclusions: Solutions

Biocontrol and IPM offer alternatives to pesticides.

Further research and experience with GM crops may eventually resolve questions about impacts, and allow us to maximize benefits while minimizing harm.

More funding for seed banks can rebuild crop diversity.

Ways are being developed to make feedlot agriculture and aquaculture safer and cleaner.

conclusions solutions83
Conclusions: Solutions

Organic farming is popular and growing fast.

Green revolution advances have kept up with food demand so far. Improved distribution and slowed population growth would help further.

Farming strategies like no-till farming, contour farming, terracing, etc., help control erosion.

Government laws, and government extension agents working with farmers, have helped improve farming practices and control soil degradation.

Better grazing and logging practices exist that have far less impact on soils.



Sustainable Agriculture



Soil erosion

Soil salinization

Aquifer depletion



Loss of


Loss of prime


Food waste

Subsidies for unsustainable

farming and fishing

Population growth


High-yield polyculture

Organic fertilizers

Biological pest control

Integrated pest


Irrigation efficiency

Perennial crops

Crop rotation

Use of more water-

efficient crops

Soil conservation

Subsidies for more sustainable farming and



What Can You Do?

Sustainable Agriculture

  • Waste les food
  • Reduce or eliminate meat consumption
  • Feed pets balanced grain foods instead of meat
  • Use organic farming to grow some of your food
  • Buy organic food
  • Compost your food wastes
question review

Integrated pest management may involve all of the following EXCEPT… ?

a. Close population monitoring

b. Biocontrol

c. Exclusive reliance on pesticides

d. Habitat modification

e. Transgenic crops

question review88

What do seed banks do?

a. Lend money to farmers to buy seeds

b. Pay farmers to store seeds

c. Buy seeds from farmers

d. Store seeds to maintain genetic diversity

e. None of the above

question review89

Which is NOT a benefit of aquaculture?

a. Provides a reliable protein source

b. Reduces pressure on natural fisheries

c. Produces no waste

d. Uses fewer fossil fuels than commercial fishing

e. All of the above are benefits

question weighing the issues
QUESTION: Weighing the Issues

Can we call the green revolution a success?

a. A huge success; it has saved millions from starvation because it increased food production to keep pace with population growth.

b. Not a success; its environmental impacts have outweighed its claimed benefits.

c. A success; its environmental impacts are balanced by the fact that it saved huge areas from deforestation.

question interpreting graphs and data
QUESTION: Interpreting Graphs and Data

With 500 kg of water, you could produce … ?

a. 2 kg of protein from milk

b. Protein from 50 chickens

c. 750 kg of protein from beef

d. 15 eggs

Figure 9.18b

question viewpoints
QUESTION: Viewpoints

Should we encourage the continued development of GM foods?

a. Yes; they will bring many health, social, and environmental benefits.

b. No, we should adopt the precautionary principle, and not introduce novel things until we know they are safe.

c. Yes, but we should proceed cautiously, and consider each new crop separately.

question review93

Which statement is NOT correct?

a. Soil consists of disintegrated rock, organic matter, nutrients, and microorganisms.

b. Healthy soil is vital for agriculture.

c. Soil is somewhat renewable.

d. Soil is lifeless dirt.

e. Much of the world’s soil has been degraded.

question review94

The A horizon in a soil profile… ?

a. Is often called the “zone of accumulation.”

b. Is often called “topsoil.”

c. Contains mostly organic matter.

d. Is the lowest horizon, deepest underground.

question review95

Erosion occurs through… ?

a. Deforestation.

b. Excessive plowing.

c. Overgrazing rangelands.

d. Two of the above.

e. All of the above.

question review96

Drip irrigation differs from conventional irrigation in that … ?

a. It is much less efficient.

b. It can cause salinization.

c. Water is precisely targeted to plants.

d. About 40% is wasted.

question weighing the issues97
QUESTION: Weighing the Issues

You are farming an extremely steep slope that is sunny and very windy. What strategies would you consider using?

a. Crop rotation

b. Contour farming

c. Intercropping

d. Terracing

e. Shelterbelts

f. No-till farming

question interpreting graphs and data98
QUESTION: Interpreting Graphs and Data

Grain produced per person has… ?

a. Risen steadily

b. Fallen sharply

c. Increased since 1983

d. Decreased since 1983

Figure 8.3