soil and food
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Soil and Food
Soil: What is it?1. Inorganic
materials (clay, silt, and sand) weathered from solid rock
2. Living organisms (worms, insects, mites, fungi, …)
3. Decaying organic matter
4. Water5. air
Soil• Who cares?
Soil• Who cares?
– Critical to driving biogeochemical cycles– HNOPS in CHNOPS comes from the soil;
YOU come from the soil!•C1480H2960N16O1480P1.8S
Air Soil
Soil• How long does it take for soil to form?
Soil• How long does it take for soil to form?
–200-1,000 years for 1 inch of soil
Soil• What influences soil properties?
Soil ProfileDig into the soil and you see the soil’s
profile: all the different layers (called horizons) of soil, from the surface litter to the bedrock
Soil Horizons
Topsoil
Zone of Leaching
Subsoil
Parent MaterialBedrock
Surface Litter
Surface Litter and Topsoil
Soil • Surface litter: fresh and partly decomposed
organic matter • Topsoil: where most living things and
nutrients are• Zone of leaching: where dissolved materials
from above move down• Subsoil: accumulated materials from above• Parent material: partially broken down
rock; source of minerals and inorganic matter in soil
• Bedrock: underlying, unweathered rock
Not all soils have the same
profile
Let’s look at tropical
soils
Tropical rainforest soil• Have a shallow topsoil layer because of
rapid decomposition• Lots of rainfall removes a lot of the
silica from the topsoil, but leaves behind metals like aluminum and iron.
• If you remove the plants, the topsoil washes away
Tropical rainforest soil• Leaving behind the metal-rich subsoil,
which hardens in the sunlight, eventually turning into a hard, red soil/dirt that doesn’t absorb water and can’t support plants
• Can grow crops there for 3 yrs or so• Then switch to cattle for another 3-5 yrs• And then land is abandoned
Tropical rainforest soil• So, what is the take-home message?
– Where we grow crops is not just determined by climate; soil type must be considered.
Types of soil profiles:
• Soils have been cataloged all over the U.S. and most of the world, at this point in time.
• See next two slides…
U.S. Soil Map
Soil Profile and Information for the Tucson Area
Human impacts on soils• Soil erosion: movement of soil
components (esp. topsoil) from one place to another
Types of soil erosion
Figure 8.11
Splash erosion
Rill erosion
Gully erosion
Sheet erosion
Human impacts on soils• How is soil moved?
– 1. Wind– 2. Moving water
Human impacts on soils• What are the rates of soil erosion?
– In U.S., for 1/3 of all cropland, erosion rates exceed replacement rates for soil
– Amount of topsoil lost in the U.S. each year would fill a dumptruck 3,500 miles long
Human impacts on soils• Where does the soil go?
– Oceans– Somewhere else … where it’s not useful as
soil anymore...
Human impacts on soils• What factor makes the land more
susceptible to erosion?– VEGETATION REMOVAL
• Why?–1. Vegetation (roots) hold the soil in
place–2. Plants slow down wind and running
water (less energy)
Human impacts on soils: erosion
• Type Tons soil eroded % rain that runs off• Bare soil 41 tons/hectare 30%
Human impacts on soils: erosion
• Type Tons soil eroded % rain that runs off• Bare soil 41 tons/hectare 30%• Continuous corn 19.7 tons/hectare 29%
Human impacts on soils: erosion
• Type Tons soil eroded % rain that runs off• Bare soil 41 tons/hectare 30%• Continuous corn 19.7 tons/hectare 29%• Continuous wheat 10.1 tons/hectare 23%
Human impacts on soils: erosion
• Type Tons soil eroded % rain that runs off• Bare soil 41 tons/hectare 30%• Continuous corn 19.7 tons/hectare 29%• Continuous wheat 10.1 tons/hectare 23%• Rotate corn,
wheat, clover 2.7 tons/hectare 14%
Human impacts on soils: erosion
• Type Tons soil eroded % rain that runs off• Bare soil 41 tons/hectare 30%• Continuous corn 19.7 tons/hectare 29%• Continuous wheat 10.1 tons/hectare 23%• Rotate corn,
wheat, clover 2.7 tons/hectare 14%• Continuous
bluegrass 0.3 tons/hectare 12%
– Based on 14 years of data from the Missouri Experiment Station, Columbia, Missouri
Human impacts on soils: erosion
• So, what was the take-message of that last table?
Human impacts on soils: erosion
• So, what was the take-message of that last table?– Amount and type of vegetation affects the
amount of erosion of soil that occurs
Human impacts on soils: erosion
• What activities lead to soil erosion?
Effects of Soil Erosion– 1. Loss of productivity of the land
• Less soil, less nutrients, less water-holding capacity …. Less growth
Effects of Soil Erosion– 2. Increased air and water pollution
• From dust in the air and soil in the water...
Effects of Soil Erosion– 3. Increased flooding: due to less water
holding capacity of the soil
Effects of Soil Erosion– 4. Increased gullying: thus loss of
productive land.
Effects of Soil Erosion– 5. Increased costs due to buying fertilizer,
irrigation, etc.
Effects of Soil Erosion– 6. More irrigation leads to salinization of
soils and eventually waterlogging (as a farmer attempts to flush out the salts…)
Human impacts on soils: conservation
• 1930s dust bowl was a wake-up call (in U.S.)
• 1935 Soil Conservation Act established Soil Conservation Service: maintains soils in the U.S. using education, laws, incentives, disincentives...
Soil Conservation Methods
Food
United States: The Revis family of North CarolinaFood expenditure for one week: $341.98
Chad: The Aboubakar family of Breidjing CampFood expenditure for one week: $1.23
From the book, "Hungry Planet"
Food• Malthus, 1700s:
– Population is increasing exponentially– Food resources are increasing linearly – ………… BIG problem!
Food–Malthus didn’t/couldn’t anticipate the
industrial and green revolutions, which have allowed food resources to increase exponentially for the last few 100 y
Food• BUT• Is this maxed out?
Per capita food production is leveling off world wide
Food: Grain harvests– World grain production has been increasing
thru time– But production per person has leveled off,
area under production has leveled off, and the grain harvested area per person has decreased
Food• So, do you think we will be able to
supply enough food for everyone in the future?
• Depends on– Rate of population growth– Ability to increase food availability
Food• Let’s talk about our food for a minute. • What do we eat?
– 2 main crops make up 60% of our calories• 1.• 2.
– 2 other crops make up most of the rest• 3.• 4.
?
Food• Let’s talk about our food for a minute. • What do we eat?
– 4 main crops• 1. Wheat• 2. Rice
• 3. Corn• 4. Potatoes
Food• What do we eat?
– 4 main crops• 1. Wheat 3. Corn• 2. Rice 4. Potatoes
Problems?– 1. These are all annuals that require yearly
planting and soil disturbance...
FoodProblems?– 1. These are all annuals that require yearly
planting and soil disturbance...– 2. Having just a few big producers
• Reduces genetic variability• Which reduces chances of adapting if
there is a change (disease, climate change….)
Solutions?
FoodWe need to diversify our food sources: more
strains, more types of food
Food• What do we eat?
– 8 non-fish domesticated livestock types provide the bulk of our non-plant diet. What are they?
Food• What do we eat?
– 8 non-fish domesticated livestock types provide the bulk of our non-plant diet. What are they?• Pig, goat, sheep, cow, duck, turkey,
chicken, rabbit
Food• How do we make more food available to
the world market?– 1. Put new land into production– 2. Increase yields– 3. Improve use of existing food supply
Food• How do we make more food available to
the world market?– 1. Put new land into production
• The land that isn’t in production right now is not in production for a reason! So, there really isn’t that much new land for food production. Plus, land is being urbanized and we are losing agricultural land...
Food• How do we make more food available to
the world market?– 2. Increase yields
• Industrial and green revolution: farm machinery, pesticides, fertilizer, irrigation, higher yielding crop varieties. All of this has increased yields over the past 150 y, but we are maxing out on pesticides, fertilizer, irrigation.
Food• How do we make more food available to
the world market?– 3. Improve use of existing food supply
• A) feed lower on the food chain–90% of all U.S. grain is fed to livestock
Food• How do we make more food available to
the world market?– 3. Improve use of existing food supply
• B) develop better food preservation techniques–Losses up to 30%
Food• How do we make more food available to
the world market?–3. Improve use of existing food supply
• C) better food distribution–Drought and/or civil war areas: loss of infrastructure, diversion of “man” power from fields...
Food• How do we make more food available to
the world market?– 3. Improve use of existing food supply
• feed lower on the food chain• develop better food preservation
techniques• better food distribution• education: Improve nutrition
Food• Integrated Pest Management: yet
another thing that could help
Food• Integrated Pest Management: using a
combination of approaches to reduce pests, improve yields
Food• Integrated Pest Management• Approaches:
– 1. Modify cultivation procedure: crop rotation, multi-cropping, ...
Food• Integrated Pest Management• Approaches:
– 1. Modify cultivation procedure– 2. Artificial selection and genetic
engineering
Food• Integrated Pest Management• Approaches:
– 1. Modify cultivation procedure– 2. Artificial selection and genetic
engineering– 3. Biological control of pests
Food• Integrated Pest Management• Approaches:
– 1. Modify cultivation procedure– 2. Artificial selection and genetic
engineering– 3. Biological control of pests– 4. Insect traps and sterilization
Food• Integrated Pest Management• Approaches:
– 1. Modify cultivation procedure– 2. Artificial selection and genetic
engineering– 3. Biological control of pests– 4. Insect traps and sterilization– 5. Chemical use only as a last resort
Food• Integrated Pest Management• Approaches:
– 1. Modify cultivation procedure– 2. Artificial selection and genetic
engineering– 3. Biological control of pests– 4. Insect traps and sterilization– 5. Chemical use only as a last resort– 6. Change consumer attitude: blemishes,
etc.
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