Soil, Agriculture, and Hunger

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Soil, Agriculture, and Hunger
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Things well talk about

• Soil formation, characteristics

• Soil erosion

• Hunger and malnutrition

• Agricultural practices

• Feeding the worlds hungry

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Soils Formation

• Soil horizons

• Soil profile

• Humus

E horizon Leaching zone
R horizon bedrock
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Soil Types
Mosaic of closely packed pebbles, boulders
Alkaline, dark, and rich in humus
Weak humus- mineral mixture
Dry, brown to reddish-brown, with variable
accumulations of clay, calcium carbonate,
and soluble salts
Clay, calcium compounds
mollisol
Desert Soil (hot, dry climate)
Grassland Soil (semiarid climate)
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Laterite (a clay) - ironstone
Forest litter leaf mold
Acidic light- colored humus
Humus-mineral mixture
Light, grayish- brown, silt loam
Iron and aluminum compounds mixed with clay
Dark brown Firm clay
Tropical Rain Forest Soil (humid, tropical
climate)
Deciduous Forest Soil (humid, mild climate)
oxisol
alfisol
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Soil Components-What is dirt?

• Inorganic minerals

• Organic matter

• Water and air

• Living organisms

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Inorganic minerals

• 45 of volume

• Macronutrients
• -nitrogen, phosphorus, potassium (NPK)
• -calcium, magnesium, sulfur

• Micronutrients (trace elements)
• -iron, copper, zinc

• Limiting factors

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Organic Matter

• 1-7 of volume

• Humus
• - helps retain water
• - helps retain water-soluble nutrients
• - potassium, magnesium, ammonia
• - serves as food for soil organisms
• - provides future soil nutrients

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Water and Air

• 50 of volume

• Fills pore spaces

• Different soils have different pore size
• - sand - large
• - silt - medium
• - clay - small

• Water for photosynthesis, air for
• respiration

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Living Organisms

• 0.1 of volume

• Bacteria, fungi, molds, nematodes,
• earthworms, insects, mammals

• Actions contribute to soil fertility, porosity

• Burrowing, feces, slime, secretions, death

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Soil Determining Factors

1. Parent material
2. Climate
3. Abrasion
4. Organisms
5. Topography
6. Time

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Parent Material

• Rocksgtgtweatheringgtgtinorganic minerals

• Residual soils - develop on bare rock
• during primary succession

• Transported soils - deposited in areas
• by actions of wind, water, glaciers,
• humans

• Floodplain soils (1/3 of croplands)

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Climate

• Weathering of parent material

• Heating, cooling, ice, rain (acidic)

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Abrasion

• Physical breakdown

• Rub rocks together

• Wind, water, glaciers

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Organisms

• Plant roots enlarge cracks

• Burrowing helps aerate

• Feces, death build up organic matter

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Topography

• Steep areas subject to more
• weathering, but reduced
• accumulation

• Flat areas subject to less weathering,
• but higher accumulation
• - deposits of transported soils

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Time

• Period of weathering

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Soil Properties - Physical

• Infiltration

• Leaching

• Porosity/permeability

• Texture

• Loam

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Texture effects on soil characteristics
Texture Nutrient Infiltration Water-Holding Aerati
on Tilth Capacity Capacity Clay Good Poor Good
Poor Poor Silt Medium Medium Medium Medium Medium
Sand Poor Good Poor Good Good Loam
Medium Medium Medium Medium Medium
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Soil Properties - Chemical

• pH - acidity, alkalinity
• 1-6 acidic 7 neutral 8-14 alkaline
• - acidity produced by rain (pH 5.5), organic
  matter
• breakdown, some fertilizers

• Crops have pH preferences
• neutral - alfalfa acidic - corn, wheat
• very acidic - potatoes

• Soil pH adjustment - lime (up), water (down)

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Soil Erosion

• Loss of soil by actions of wind, water

• Worldwide net loss - 23 billion tons/yr
• - eroding faster than it forms on 38 of
  croplands
• - 200-1000 years to produce 1 inch of soil

• U.S. losses - 18 tons/hectare/year
• - 0.7 per year
• - eroding 16 X faster than it is forming

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Global Soil Erosion
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Soil Erosion Contributors

• Agriculture

• Logging

• Mining

• Construction

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Poor Agricultural Practices

• Farming steep slopes

• Removing fence rows

• Moldboard plowing (in fall)

• Overgrazing

• Farming natural waterways

• Compacting soil with large machines

• Lack of crop rotation

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Dust Bowl - U.S. Great Plains

• Early 1930s

• Intensive agriculture drought

• Destroyed/damaged 90 million acres

• Led to Soil Conservation Service

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Soil Conservation Service

• Natural Resources Conservation Service

• Goal encourage proper land use
• practices to
• 1) maintain soil fertility
• 2) control erosion

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Maintaining Soil Fertility

• Organic (Natural) Fertilizers

• Stimulate growth of decomposers

• Animal and plant wastes

• More difficult to handle, apply

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Maintaining Soil Fertility

• Inorganic Fertilizers (most U.S. soils)

• NPK - may harm soil (sustained use)
• -low or no micronutrients
• - decrease soil oxygen
• - lower soils ability to produce useable N forms

• May wash into water supplies
• - more readily dissolved than manure

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Soil Erosion Control

• Conservation tillage
• - low-till or no-till

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Soil Erosion Control

• Strip cropping and contour farming

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Soil Erosion Control

• Crop rotation

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Soil Erosion Control

• Windbreaks and shelterbelts

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Soil Erosion Control

• Terracing

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Soil Erosion Control

• Not planting marginal lands

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Soil Erosion Control

• Grass waterways

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Soil Erosion Control

• Rotational grazing

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Agriculture

• Industrialized agriculture
• - mechanized
• - energy supplement from fossil fuels

• Non-industrialized agriculture
• - unmechanized
• - energy supplement from
• humans and animals

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Industrialized Agriculture in U.S.

• Nations largest industry
• - 20 of labor force
• - 1 person feeds 77
• - reduces labor by 99
• - yield 4 X higher
• - doubled food production in 150 years

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Industrialized Agriculture in U.S.

• Major problem
• - energy intensive
• - may require up to 9 units of
• supplemental energy to produce
• 1 unit of food energy
• - non-mechanized ag yields 3 units of
• food energy for each unit of
• supplemental energy (27 X better)

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Combating Hunger and Malnutrition

• Producing more food

1) Cultivate more land
2) Improve crop yields
3) Catch, raise more fish seafood
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Cultivating More Land

• Problems with 56 of potential croplands

• Remote location

• Insect infestation

• Poor soils, lack of water

• High costs, no economic incentives

• Competition for other uses

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Improving Crop Yields

• Develop higher-yield varieties

• Quickest and cheapest way
• - better adapted to climate, soil conditions
• - wheat, rice

• Problem require more fertilizer, water,
• pesticides
• - weaker plants
• - seeds more costly for farmers in
• developing nations

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Catching, Raising More Fish

• Supplies 25 of animal protein

• Increasing demand, level or declining
• catches
• - reached or exceeded MSY
• - fish not abundant, higher trophic levels
• - shrimp 175 energy ratio

• Alternatives?
• - krill, aquaculture

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Can simply producing more foodsolve the worlds
hunger andmalnutrition problem?

• Poverty is chief cause of hunger,
• malnutrition

2) Inadequate distribution system
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Can simply producing more foodsolve the worlds
hunger andmalnutrition problem?

• Livestock gets most of the crops
• - enough to feed 16 billion people

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Can simply producing more foodsolve the worlds
hunger andmalnutrition problem?

• Food must be of proper quality and
• quantity
• - marasmus - skinny, bloated belly
• - diet low in calories and protein
• - kwashiorkor - entire body bloated
• - diet high in calories, low in protein

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Can simply producing more foodsolve the worlds
hunger andmalnutrition problem?
5) Food must be culturally acceptable
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Alternatives to producing more food

• Simplifying diets
• Use and waste less food, fertilizer
• Use new, unconventional, enriched,
• and fabricated foods
• Reduce crop losses from pests,
• diseases

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Simplifying Diets

• Eating lower on the food web

• 1/3 of world grain production used to support
• meat diets of people in developed nations

• U.S. citizens eat 25 X more meat than people in
• developing nations

• 75 of N. Amer. grain goes to cattle (lt5 in
• developing nations)

• Eliminate U.S. feedlots
• - food for 400 million people

• 10 meat reduction - 60 million people

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Use, Waste Less Food

• Wasted food - cafeterias, homes, etc.

• Overnutrition
• - 30-50 of adults, 10 of children

• Fertilizer use on non-ag land
• - food for 65 million

• Pets
• - food for 21 million

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New, Unconventional, Enriched, Fabricated Foods

• 80,000 edible plants, 175 cultivated,
• - 16 important, 3 biggies
• - corn, wheat, rice

• New crop plants - winged bean, ye-ed

• Unconventional foods - insects!
• - high protein

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New, Unconventional, Enriched, Fabricated Foods

• Enriched foods
• - combat malnutrition, disease, by
• adding vitamins, minerals
• - salt with iodine - goiter
• - rice with vitamin B1 - beriberi

• Problem added during processing,
• may be unavailable to those who
• grow your own

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New, Unconventional, Enriched, Fabricated Foods

• Fabricated foods
• - substitute plant products for animal
• - margarine for butter
• - veg. oil for lard
• - imitation bacon (soybeans, wheat)
• - soy burgers (soybeans, edible mold)
• - high protein

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Reduce Crop Losses from Pests, Diseases

• 45 of potential crops destroyed
• each year
• - 33 before harvest
• - 12 during storage

• More use of pesticides needed?
• - similar losses in U.S. where pesticide
• use is high and other countries where
• use is low

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Pesticide Problems

• Persistence

• Bioaccumulation/biomagnification
• - DDT and the bald eagle

• Nonspecificity

• Development of resistance

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Biological Controls Alternatives

• Predators or parasites

• Attractants (pheromones sex hormones)

• Sterilization

• Resistant crops (genetic)