Chapter 7 Food and Agriculture

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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

• World food supplies: 1950 versus 2000• Within families that don't get enough to eat,

women and children have the poorest diets• 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

Chronic Hunger and Food Security

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 use 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 high-quality 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

• Wheat, rice and maize (grasses) are responsible for the majority of the world's nutrients.

• Potatoes, barley, oats and rye are staples at high latitudes with cool, moist climates.

• Cassava, sweet potatoes, and other roots and tubers are staples in warm wet climates.

• Sorghum and millet are drought resistant and are staples in dry regions of Africa.

• Fruits, vegetables and vegetable oils contain high levels of vitamins, minerals, dietary fiber and complex carbohydrates.

Crops

Annual Production of Important Foods

Below - Rice plants (a type of grass or grain)

USDA Food Pyramid (current version)

Meat, Milk, and Seafood

• Milk and meat are highly prized, but their distribution is inequitable. Developed countries (20% of world population) 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 over-harvesting and habitat destruction.

Issues with 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, air, water, 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 - soilsare stratified intohorizontal layerscalled soil horizons,and together they make up the soil profile

May not have all layers at a given location

PART 4: WAYS WE USE & ABUSE SOIL

Much potential cropland suffers from constraints.

• 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.

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.

• Erosion – an important natural

process, resulting in redistribution of the products of geologic weathering

– part of both soil formation and soil loss.

– tends to begin subtly.• Worldwide, erosion

reduces crop production by the equivalent of 1% of world’s 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.

– Also useful: calcium, magnesium, sulfur

• Problems with fertilizer use– Excess washes off of fields, into surface

water bodies– Eutrophication

• Excess nutrients• Overgrowth of algae/plants

– When these die, they decay, consuming available oxygen

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 (“organic crops”) tend to have lower yield, but have lower operating costs and less ecological damage (they cost more for the consumer because of the yield).

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 present 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 are from technological advances and modification of a few well-known 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.

Genetic Engineering• Genetic engineering is the splicing of a

gene from one organism into the chromosome of another.

• These Transgenic organisms are called Genetically Modified Organisms (GMOs)

• 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 species (plants that live >2 years)

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.