and Food Agriculture
I. NUTRITION AND FOOD SUPPLIES
A. The most common dietary problem in wealthy countries is over-nutrition.
B. Malnourishment - Nutritional imbalance
1. Iron deficiency is the most common dietary imbalance in the world; leads to
anemia, hemorrhage during childbirth; affects development
2. Protein Deficiency Diseases
a) Kwashiorkor - Displaced Child - Occurs mainly in children whose
diet lacks high-quality protein.
b) Marasmus - To Waste Away - Caused by a diet low in both protein
and calories.
C. Famines
1. Characterized by large-scale food shortages, mass starvation, social
disruption, and economic chaos.
a) Mass migrations due to loss of productive capacity
b) Environmental conditions are trigger, but politics and economics are
often underlying problems.
2. Foreign aid distributes surplus commodities and produces feeling of
generosity.
3. Food/refugee camps have serious problems
II. MAJOR FOOD SOURCES
A. Three crops deliver majority of worlds nutrients: Wheat, Rice and Corn
B. Potatoes, barley, oats and rye are staples in cool, moist climates.
C. Cassava, sweet potatoes, and other roots and tubers are staples in warm wet climates.
D. Meat and Dairy: Protein-rich foods
1. Globally, 660 M metric tons of cereals are used to feed livestock.
E. Seafood
1. Seafood is an important protein source in many countries.
2. Annual catches of ocean fish rose by 4% annually between 1950-1988.
3. Since 1989, 13 of 17 major fisheries have declined or become commercially
unsustainable.
III. SOIL: A complex mixture of weathered minerals, partially decomposed organic materials,
and a host of living organisms.
A. At least 20,000 different soil types in the U.S.
B. Soil Ecosystems: often unseen, can be quite complex
C. Soil Profiles: stratified into layers called soil horizons.
1. O Horizon (Organic layer)
2. A Horizon (Topsoil)
3. E Horizon (Leached)
4. B Horizon (Subsoil)
5. C Horizon (Parent Material)
IV. WAYS WE USE AND ABUSE SOIL
A. Approximately 11% of the earths land area is in agricultural production.
B. Land Resources
1. In developed countries, 95% of ag. growth is in chemical agriculture
2. Less land cultivated in North America now than 100 years ago.
3. Many developing countries are reaching limit of usable land
C. Land Degradation
1. Annual: 3 Mha of cropland destroyed by erosion, 4 Mha desertified, and 8
Mha converted to non-agricultural uses.
2. Definitions of degradation are based on both biological productivity and
expectations of what land should be like.
a) Soil is impoverished or eroded
b) Run-off is contaminated
c) Biodiversity is diminished.
V. EROSION
A. Erosion is an important natural process
B. Mechanisms of Water Erosion
1. Sheet Erosion Thin layer of soil removed.
2. Rill Erosion Rivulets of running water cut small channels.
3. Gully Erosion Rills too large to be removed by normal tillage.
4. Streambank - Erosion Washing away of soil from established banks.
C. Mechanisms of Wind Erosion
1. Row crops leave soil exposed
2. Weed free-fields
3. Removal of windbreaks
4. No crop-rotation or resting periods
5. Continued monocultures
VI. AGRICULTURE AND WATER
A. Agriculture accounts for largest single share of global water use.
B. As much as 80% of water withdrawn for irrigation never reaches crops
C. Soil problems: waterlogging, salinization
D. Fertilizer
1. Lack of critical nutrients often limits plant growth
2. Adding fertilizer stimulates growth and increases yields
3. Manure and nitrogen-fixing bacteria are alternative methods of replenishing
soil nutrients
E. Alternative tillage methods can return nutrients to soil
VII. SUSTAINABLE AGRICULTURE
A. Methods:
1. Strip Farming
2. Contour Plowing
3. Terracing
B. Energy
1. Farming in industrialized countries is highly energy-intensive.
2. Between 1920-1980, energy use rose directly with mechanization
3. Altogether, U.S. food system consumes 16% of total energy use
C. Pest Control
1. Biological pests reduce annualcrop yields by up to 50%
2. Crops grown without synthetic fertilizers or pesticides tend to have lower
yield, but have lower operating costs and less ecological damage.
3. Strip farming, intercropping, and integrated pest management are other
options
VIII. NEW CROPS AND GENETIC ENGINEERING
A. Most world food comes from 16 crops.
1. At least 3,000 species of plants have been used for food
2. Many new / unconventional varieties might be valuable food supplies.
3. Most major improvements in farm production have come from technological
advances and modification of a few well-known species.
a) Corn
b) Dwarf varieties.
4. Green Revolution - Spread of new varieties around the world.
B. Genetic Engineering
1. Genetically Modified Organisms (GMOs) contain DNA possessing genes
borrowed from unrelated species.
a) Can produce crops with pest-resistance etc.
b) Opponents fear traits could spread to wild varieties
2. 60% of all processed foods in N. America contain transgenic products.
3. Genetically engineered crops: golden rice
IX. SOIL CONSERVATION
A. Providing Ground Cover
B. Leave crop residue after harvest.
C. Plant cover crops after harvest.
D. Mulch
E. Reduced Tillage
1. Minimum Till - Chisel plow
2. Conserv-Till - Coulter (Disc)
3. No-Till - Drilling
F. Often farmers using conservation tillage must depend relatively heavily on pesticides.
G. Traditional tillage helped control weeds and pests.
Ischemicalagriculturenecessaryto
feedpeopleandpreservewildlands?
Yes
No
3540MacresinUSisinCRP;
whynotrotate?
Populationisgrowing
Weshouldmaximizeyieldonhigh
qualitylandtohelpconserve
Otherlandscouldbeusedfor
wildlands
Conversionofmarginalcroplands
wouldendangerwildlife
Socialconcerns
specializedcrops
Chemicalsusedarebuildingup,
harmingtheenvironment,and
endangeringhumanhealth