Transcript Document

Chapter 7
Food and Agriculture
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter Seven Topics
•
•
•
•
•
•
•
Food and Nutrition
Major Food Sources
Soil: A Renewable Resource
Ways We Use and Abuse Soil
Other Agricultural Resources
New Crops and Genetic Engineering
Sustainable Agriculture
Part 1: Nutrition and Food Supplies
Chronic Hunger and Food Security - within
families that don't get enough to eat, women and
children have the poorest diets.
• World food supplies: 1950 versus 2000
• Richer countries: the most common dietary
problem is over-nutrition (obesity)
• Sub-Saharan Africa: food production has not
kept pace with rapid population growth
• Asia: most rapid increase in crop production
and this accompanied rapid population
growth
Countries at risk for inadequate nutrition
On the left is shown the number and
proportion of chronically
undernourished people in developing
regions. The most hungry people live
in East and South Asia. Persistent
hunger is a major problem in Africa
where the problem is getting worse.
Famines are characterized by large-scale food
shortages, massive starvation, social disruption,
and economic chaos. Some causes are:
• Environmental
conditions - drought,
insects, natural
disasters
• National politics corruption, oppression
• Armed conflict
• Economics - price
gouging, poverty,
landlessness
Essential Nutrients
• Malnourishment - a nutritional imbalance caused by
a lack of specific dietary components or an inability to
utilize essential nutrients
• Starchy foods like corn and polished rice tend to be
low in several essential nutrients.
• Protein deficiency diseases - kwashiorkor,
marasmus (see next slide).
• Iron deficiency (anemia) - is the most common dietary
deficiency in the world and is most severe in India.
• Iodine deficiency - causes goiter, hyperthyroidism
Protein Deficiency Diseases
• Kwashiorkor - "Displaced
Child" - Occurs mainly in
children whose diet lacks highquality protein.
•Marasmus - "To Waste
Away" - Caused by a diet low
in both protein and calories.
Obesity - The most common dietary problem in
wealthy countries is over-nutrition.
PART 2: MAJOR FOOD SOURCES
Crops
• Wheat, rice and maize) are responsible for the majority of the
world's nutrients.
• Potatoes, barley, oats and rye are staples at high latitudes
with cool, moist climates.
• Potatoes, barley, oats and rye are staples in cool, moist
climates.
• Cassava, sweet potatoes, and other roots and tubers are
staples in warm wet climates.
• Sorghum and millet are drought resistant and staples in dry
regions of Africa.
• Fruits, vegetables and vegetable oils contain high levels of
vitamins, minerals, dietary fiber and complex carbonhdrates.
Annual Production of Important Foods
Below - Rice plants (a
type of grass or grain)
Eating a Balanced Diet as Determined by
USDA Food Pyramid
Meat, Milk, and Seafood
• Milk and meat are highly prized, but their distribution is
inequitable. Developed countries make up 20% of
world population, but consume 80% of meat and milk
production. Less developed countries produce 60% of
world's milk and meat.
• About 90% of the grain grown in North America is
used to feed cattle, hogs, poultry, and other animals!
• Seafood is an important protein source in many
countries. This food source is threatened by overharvesting and habitat destruction.
Environmental Issues with Raising Beef
• Every 16 kg of grain and soybeans fed to beef cattle in
feedlots produce 1 kg of edible beef.
– If we ate grain directly, we would obtain twenty-one times more
calories and eight times more protein than we get eating the beef.
PART 3:SOIL - A VALUABLE RESOURCE
• Soil - a complex mixture of weathered minerals,
partially decomposed organic matter and a host of
living organisms
• We depend on soil for life, yet tend to take this
living resource for granted.
• U.S. has > 20,000 different soil types that vary
due to influences of parent material, time,
topography, climate and organisms
• About 30-50% of the world's croplands are losing
topsoil faster than it can be replaced
• Soil is a renewable resource, but building good
soil is a slow process.
Soil Organisms
Without soil organisms, the earth would be
covered with sterile mineral particles.
Soil Profile - soils
are stratified into
horizontal layers
called soil horizons,
and together they
make up the soil
profile
PART 4: WAYS WE USE & ABUSE SOIL
• Approximately 11%
of the earth's land
area is currently in
agricultural
production.
– Up to four times as
much could potentially
be converted to
agricultural use.
Much potential cropland
suffers from constraints.
• Much of this additional
land suffers from
constraints.
Land Resources
• Cropland per person averages only 0.7 acres
worldwide. By 2025, this could decline to 0.42
acres.
• In developed countries, 95% of recent
agricultural growth has come from improved
crop varieties or increased fertilization,
irrigation, etc.
• Land conversion involves ecological trade-offs
• Many developing countries are reaching limit of
lands that can be exploited for agriculture
without unacceptable social and environmental
costs.
Areas of Concern for Soil Degradation
Erosion: The Nature of the Problem
• Erosion is an important
natural process,
resulting in
redistribution of the
products of geologic
weathering, and is part
of both soil formation
and soil loss.
– Tends to begin subtly.
• Worldwide, erosion
reduces crop
production by
equivalent of 1% of
world cropland per
year.
Mechanisms of Erosion
• Sheet Erosion - Thin, uniform layer of soil
removed.
• Rill Erosion - Small rivulets of running water
gather and cut small channels in the soil.
• Gully Erosion - Rills enlarge to form channels
too large to be removed by normal tillage.
• Streambank Erosion - Washing away of soil
from established stream banks.
Mechanisms of Erosion (continued)
• Wind can equal or
exceed water as an
erosive force, especially
in a dry climate and on
flat land.
– Intensive farming practices:
•
•
•
•
Row crops leave soil exposed
Weed free-fields
Removal of windbreaks
No crop-rotation or resting
periods
• Continued monocultures
PART 5:OTHER AGRICULTURAL RESOURCES
•
•
•
•
Water
Fertilizer
Energy
Pesticides
Agriculture is the biggest global consumer of water, but there are
many ways we can reduce water use (above - downward facing
sprinklers deliver water more efficiently than upward-facing ones).
Fertilizer
• Lack of nitrogen, potassium, and phosphorus
often limits plant growth.
– Adding nutrients via fertilizer usually stimulates growth
and increases crop yields.
• 1950 - Average of 20 kg/ha fertilizer used.
• 2000 - Average of 90 kg/ha fertilizer used.
– Manure and nitrogen-fixing bacteria are alternative
methods of replenishing soil nutrients.
Pest Control
• Biological pests reduce crop yields and spoil
as much as half the crops harvested annually.
– Estimated up to half current crop yields might be lost in
the absence of pesticides.
• Crops grown without synthetic fertilizers or
pesticides tend to have lower yield, but have
lower operating costs and less ecological
damage.
Up to 90% of all
pesticides never
reach target
organisms.
PART 6: NEW CROPS & GENETIC
ENGINEERING
•
At least 3,000 species of plants have been
used for food at some point in time, but
most world food comes from 16 crops..
– Many new or unconventional varieties
might be valuable food supplies.
– Winged-bean - can eat all
parts and grows in new, warm
habitat
– Triscale - drought resistant
and grows in light, sandy,
infertile soil
•
•
So far, the major improvements in farm
production have come from technological
advances and modification of a few wellknown species.
The green revolution refers to the global
spread of new, high-yield varieties of
plants. These varieties are "High
responders" to optimum levels of fertilizer,
water, pesticides, light, etc.
Green Revolution "Miracle Crop" Yield
Genetic Engineering
• Genetic engineering is the splicing a gene
from one organism into the chromosome of
another.
• These Transgenic organisms are called
Genetically Modified Organisms (GMOs)
produced
• These new genes result in plants with pest
resistance, built in weed control and wider
tolerances
• Opponents fear traits could spread to wild
varieties, and increased expense would
largely hurt smaller farmers.
Transgenic Crop Field Releases
PART 7: SUSTAINABLE AGRICULTURE
• Sustainable agriculture (regenerative
farming) - goal is to produce food and fiber on
a sustainable basis and to repair damage
caused by destructive practices. Soil is
essential to sustainable agriculture.
• Soil conservation - land management,
ground cover, climate, soil type and tillage
system are important elements in soil
conservation.
Ways to Manage Topography
• Contour - Plowing and
planting across (with the
contour) slope to slow
flow of water (left).
• Strip-farming - Planting
different crops in
alternating strips along
land contours (left).
• Terracing - Shaping land
to create level shelves of
earth again with the
slope to hold water and
soil (see next slide).
• Planting perennial
(plants that live >2 years)
species
Flooded terraces for
growing rice in China
Providing Ground Cover
Providing Ground Cover and Reducing Tillage
Methods Used to Reduce Bare Ground Erosion
• Providing Ground Cover
• Leave crop residue after harvest.
• Plant cover crops after harvest.
• Add protective ground cover such as manure, wood
chips, straw, leaves, etc. (mulch).
• Reduced Tillage
– Minimum Till - Chisel plow or ridge-tilling
– Conserv-Till - Coulter (Disc)
– No-Till - Drilling
• Often farmers using conservation tillage must
depend relatively heavily on pesticides.
Cocoa pods (left) are
growing directly on
branches of a shadetolerant tree native to
warm, moist lowland
forests of the tropics. In
contrast, coffee is native to
cool, mountain forests of
the tropics.
Organic and Locally Grown Foods