Food and Agriculture ppt


Dec 14, 2012 (5 years and 5 months ago)


Food provides

1. Energy (Calorie = amount of heat required to raise the
temperature of one kilogram of water by one degree at
one atmosphere pressure)

2. Materials to build body (carbon, proteins, minerals,
lipids, etc.)

Humans need a variety of foods to supply their
nutritional needs

Review notes from class on these nutrients:






The Food Pyramid

is a guide for what we

should eat daily.


a condition when a person does not
consume enough calories or nutrients to supply the
body’s needs

Marasmus (“wasting away”)

not enough calories and

(“displaced child”)

severe protein

bloated belly,

can cause mental



too many calories, results in health
problems including diabetes, heart disease, stroke

How do we supply 6.8 billion people with
enough food?


= practice of
raising crops and livestock for
human use and consumption


= land used to
raise plants for human use



= land
used for grazing livestock

Land devoted to agriculture
covers 38% of Earth’s land

Agriculture was invented independently by different cultures

The earliest plant and animal domestication is from the “Fertile
Crescent” of the Middle East

Wheat, barley, rye, peas, lentils, onions, goats, sheep

Traditional agriculture

= biologically powered
agriculture, using human and animal muscle power

Subsistence agriculture
= families produce only
enough food for themselves

Uses animals, irrigation and fertilizer, but not fossil

Industrialized agriculture

= using large
mechanization and fossil fuels to boost yields

Yield = amount of food that can be produced in a certain

Also uses pesticides, irrigation and fertilizers


= uniform planting of a single crop

Why might monocultures be a bad idea?

Monoculture =
a large expanse of a single crop

More efficient, increases output

Devastates biodiversity

Susceptible to disease and pests

Narrows human diet: 90% of our food comes from 15 crop
species and 8 livestock species

Armyworms easily defoliate monocultures

The Green Revolution

Dramatically increased per

Spread to the developing world
in the 1940s with wheat, rice,

Depended on large amounts of

Synthetic fertilizers

Chemical pesticides


Heavy equipment

Soil is a

thin covering over
most land that is a complex
mixture of eroded rock,
mineral nutrients, decaying
organic matter, water, air,
and billions of living
organisms, most of them
microscopic decomposers

Soil is important because:

It provides most of the
nutrients needed for
plant growth, and
subsequently consumer

It is the primary filter that
cleanses water as it passes

It is a major component
of the earth’s water
recycling and water
storage processes.

Components of soil

25% air (mostly N and O)

25% water

45% mineral

5% organic matter

Amounts of air and

water vary

Soil is a renewable resource

Formation of soil depends on 5 factors:

1. climate

3. biologic activity

5. time

2. terrain

4. geology

It takes 15 to 100s of years to form one cm of soil!

*Parent material

= the base geologic material of soil


= the continuous mass of solid rock comprising the Earth’s crust



Weathering produces soil


= the physical,
chemical, or biological
processes that break down
rocks to form soil

Physical (mechanical)

wind and rain

no chemical changes in
the parent material


substances chemically
interact with parent


organisms break down
parent material

Soil Horizons: Layers of mature soil

O horizon

organic material, leaf
litter, many organisms live here

A horizon

topsoil layer, zone of
accumulation of organic matter
and nutrients

These top 2 horizons contain:


the roots of most plants


billions of living things
(bacteria, fungi, earthworms,
insects, etc.)

Soil Horizons: Layers of mature soil

B horizon

subsoil, accumulates iron,
clay, aluminum and organic
compounds that leach down from

(leaching: process in which water
seeps down through open spaces or
pores in soil, dissolving minerals
and organic matter and carrying
them to lower layers)

Soil Horizons: Layers of mature soil

C horizon

parent material, contains
large lumps or shelves of rock

R horizon (under C horizon)


Soil Particles

Three types, based on size:

Sand: 2.0
0.05 mm

Silt: 0.05

Clay: less than 0.002mm

Relative amounts determine soil

Soil Textural Classification

Soil Permeability

Definition: the rate at which water and air move from upper to
lower soil layers

The more spaces there are between soil particles, the more
permeable it is

Plants need good drainage, but not too much

Plants are like Goldilocks

Sandy soil: This soil is too permeable

water runs right

Clay soil: This soil is too impermeable

water can’t get

Loam: This soil is just right! (mixture of sand and clay)

Which is which?

Sand on left

Loam in middle

Clay on right

Other soil characteristics that are
important to plants

Nutrient content

nitrogen, phosphorus and


if soil is too acidic or basic, plants can’t grow

Agriculture and Population Growth

The earth has a carrying capacity for the human

we don’t know what it is.

We do not have unlimited land and resources to produce
food for people.

We face food issues as our population

1. Lack of enough arable land

Graph showing per capita arable land over time:

2. Soil degradation

soil erosion

the dislodging and movement of soil by
wind or water, occurs when vegetation is absent

Erosion increases through: excessive tilling, overgrazing, and
clearing forests

Can result in desertification

most prone areas are arid and
semiarid lands

The Dust Bowl

In the late 19

and early 20th
centuries, settlers arrived in
Oklahoma, Texas, Kansas, New
Mexico and Colorado

Grew wheat, grazed cattle

Removed vegetation

A drought in the 1930s made
conditions worse

Thousands of farmers left their land
and had to rely on governmental help

Various types of soil erosion





We lose 5
7 million ha (12
17 million acres) of productive
cropland annually

3. Uneven food distribution around the

Developing countries: usually faster population growth,
more poverty, less infrastructure to grow and
distribute food

4. Problems with irrigation


= Artificially providing
water to support agriculture

Unproductive regions become


= over
irrigated soils

Water suffocates roots


= the buildup of salts in
surface soil layers

Depletion of ground and surface

5. Loss of biodiversity

When we convert natural habitats to farms, we reduce
natural habitat

We also plant monocultures and use few species for

6. Negative effects of overgrazing

Soil compaction

native invasive species invade

Less palatable to livestock

Out compete native vegetation

Ungrazed plot

Grazed plot

7. Pollution from:


pesticides, herbicides, fertilizers,

Livestock (on feedlots)

animal waste, excess methane
is a greenhouse gas

Overapplication of Fertilizer

Inorganic fertilizer use has

Overapplying fertilizer can ruin
the soil and severely pollute
several areas

Runoff causes eutrophication in
nearby water systems

Nitrates leach through soil and
contaminate groundwater

Nitrates can also volatilize
(evaporate) into the air

8. Resistance to pesticides

Some individuals are genetically immune to a pesticide

They survive and pass these genes to their offspring

Pesticides stop being effective

Evolutionary arms race
: chemists increase chemical toxicity to
compete with resistant pests

Solutions to our agriculture issues:

Sustainable Agriculture

Industrial agriculture may seem necessary, but less
agricultural methods may be better in the long run

Sustainable agriculture

= does not deplete soil, pollute water, or
decrease genetic diversity

Protecting soil: crop rotation and
contour farming

Crop Rotation

= alternating the
crops grown field from one season
or year to the next,

Cover crops protect soil when main
crops aren’t planted

Wheat or corn and soybeans

Contour Farming

= plowing
furrows sideways across a hillside,
perpendicular to its slope, to
prevent rills and gullies

Protecting soil: terracing and


= level platforms
are cut into steep hillsides,
sometimes with raised edges

A “staircase” to contain water


= planting
different types of crops in
alternating bands or other
spatially mixed arrangements

Increases ground cover

Pros and cons of no
till farming

Almost half of U.S. farmland
uses no
till farming

Benefits: reduced soil erosion,
greater crop yields, enhanced

Negatives: increased use of
herbicides and fertilizers

Biological control

Biological control

) = uses a pest’s
natural predators to control
the pest

Reduces pest populations
without chemicals

Cactus moths control prickly

Bacillus thuringiensis (Bt)

soil bacteria that kills many

Salinization prevention

It is easier and cheaper to
prevent salinization than fix it

Do not plant water
crops in sensitive areas

Irrigate with low
salt water

Irrigate efficiently, supplying
only water that the crop

Drip irrigation

targets water
directly to plants

Integrated Pest Management (IPM)

IPM uses multiple techniques to
suppress pests


Chemicals, when necessary

Population monitoring

Habitat alteration

Crop rotation and transgenic crops

Alternative tillage methods

Mechanical pest removal

Within 4 years of using IPM in Indonesia, rice yields rose 13%, and
$179 million saved by phasing out subsidies

Genetically Modified Organisms

Genetic engineering =
laboratory manipulation of
genetic material

Genetically modified

= organisms that
have been genetically
engineered by …

Recombinant DNA

created from multiple

Genetic engineering has both benefits and risks

Benefits of genetic engineering:

Increased nutritional content

Increased agricultural efficiency

Rapid growth

Disease and pest resistance

Negatives of genetic engineering:

Risks are not yet defined or well understood

Protests from environmental activists, small farmers, and
consumer advocates

Some genetically modified foods

Change diet practices

Eat less meat

Eat organic

Eat locally produced foods

Eat diverse foods

Eating animal products has
significant impacts

As wealth and commerce increase, so does consumption of meat,
milk, and eggs

Global meat production has increased fivefold

Per capita meat consumption has doubled

Domestic animal production for food increased from 7.3
billion in 1961 to 20.6 billion in 2000

Energy choices through food choices

90% of energy is lost every time
energy moves from one trophic
level to the next

The lower on the food chain from
which we take our food sources,
the more people the Earth can

Some animals convert grain

into meat more efficiently than

Environmental ramifications of eating meat

Land and water are needed to raise food for livestock

Producing eggs and chicken meat requires the least
space and water

Producing beef requires the most

When we choose what to eat, we also choose how we use resources

Organic agriculture

Organic agriculture

= Uses no synthetic fertilizers, insecticides,
fungicides, or herbicides

Relies on biological approaches (composting and biocontrol)

People debate the meaning of the word “organic”

Organic Food Production Act (1990) establishes national standards for
organic products

The USDA issued criteria in 2000 by which food could be labeled organic


World fish populations are

Technology and increased


= raising
aquatic organisms for food
in a controlled environment

Aquatic species are raised in
water pens or land
based ponds

The benefits and drawbacks of aquaculture


A reliable protein source


Reduces fishing pressure on
overharvested wild fish stocks

Energy efficient


Diseases can occur, requiring
expensive antibiotics

Large amounts of waste

Farmed fish may escape and
introduce disease into the wild

Government intervention

The Soil Conservation Service

Started in 1935, the Service works with farmers to develop
conservation plans for farms

Assess the land

Prepare an integrated plan

Work closely with landowners

Implement conservation measures

Conservation districts

= districts operate with federal
direction, authorization, and funding, but are organized
by the states

What can you do?

Eating to Save the Earth: Food Choices for a Healthy Planet
by Linda Riebel and Ken

As a consumer, you can:

Use locally grown food, or grow your own!

uses less fuel for transportation

(Example: a single fast food meal comes from Texas (meat), Nebraska (corn to feed cow),
Washington (cheese), California (lettuce and tomato), Idaho (wheat for bun and
potatoes), Louisiana (salt), Pennsylvania (ketchup), Ohio (ketchup pouches), Arkansas
(french fry box), Iowa (corn syrup for soft drink))

Buy organic

few or no pesticides or chemicals added

Go vegetarian (or nearly)

use little or no meat, dairy, eggs

Use less processed foods

stay close to the food’s natural state

Buy products with less packaging

Branch out and buy unusual products to support diversity

Consider purchasing products that support fair trade

Try not to waste food

Educate yourself and think critically