Soil and Food

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%


• Type Tons soil eroded % rain that runs off• Bare soil 41 tons/hectare 30%• Continuous corn 19.7 tons/hectare 29%


• 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%


• 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%


• 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


• So, what was the take-message of that last table?


• So, what was the take-message of that last table?– Amount and type of vegetation affects the

amount of erosion of soil that occurs


• 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"

http://www.time.com/time/photogallery/0,29307,1626519_1373690,00.html

http://www.time.com/time/photogallery/0,29307,1626519_1373704,00.html

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


– 8 non-fish domesticated livestock types provide the bulk of our non-plant diet. What are they?


– 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


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...


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.


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



• B) develop better food preservation techniques–Losses up to 30%


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...



• 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, ...


– 1. Modify cultivation procedure– 2. Artificial selection and genetic

engineering



engineering– 3. Biological control of pests



engineering– 3. Biological control of pests– 4. Insect traps and sterilization



engineering– 3. Biological control of pests– 4. Insect traps and sterilization– 5. Chemical use only as a last resort



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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Soil and Food