Transcript Agricultureal Methods and Pest Management (Chpt. 15)

Announcements – Nov. 8, 2004
Agriculture III
Lecture Objectives:
1. What alternatives to fertilizers & pesticides exist?
2. What are GMOs?
3. How do GMOs influence our lives?
4. What are the impacts of agriculture on soil?
Review

Chemical fertilizers



pros: increase yields
cons: reliance on oil, only replace nutrients,
runoff to aquatic systems
Chemical pesticides


pros: increase yields, human health,
decrease labor
cons: selects for resistance, toxic effects to
non-target organisms, persistence in
environment
Alternative Agriculture

Crop rotation

Sustainable agriculture

Organic agriculture

Integrated pest management
Crop rotation
Plant different, specific crop in a field each
year

Pros



Reduce build-up of pests specific to one crop
Retain or enhance soil nutrients
Cons


Requires more equipment
Insects developing 2-year diapause
Sustainable agriculture

Seeks ways to raise food without
degrading agricultural land and harming
surrounding ecosystems


Eliminate soil erosion & loss of productivity
Methods:


Modify traditional practices (e.g. contour
farming, conservation tillage)
Close evaluation of conditions

apply fertilizer & pesticides only where & when
needed
Organic agriculture
No chemical fertilizers or pesticides used

Animal manure as fertilizer

Crop rotation to enhance productivity &
reduce pests

Biological predators and human labor to
combat pests

Higher up-front costs, but healthier and less
damaging to environment
Integrated Pest Management

Use a variety of methods, not just chemical
pesticides, to control pests

Ecology and physiology of crop, pest
researched at universities & government
organizations

Reproduction disruption
Reproduction disruption
Intervene in reproduction process to reduce insect
numbers

Pheromone baiting



Often, males find females by following their “smell”
Synthesize female pheromones & put in traps in fields
Male sterilization



Screwworm fly female mates only once in life
Raise large numbers of males, sterilize them & release
them in environment to mate with wild females
Does not work as well in species where females mate
more than once
Plant breeding and genetic modification

Originally, selective breeding of
crops done to increase crop size,
yield, growth, etc.


Has been going on for thousands
of years
With the advent of modern
genetics, scientists can now
selectively breed and modify
crops on a whole new level.
Genetic Engineering

Genetically Modified Organisms (GMO’s)

Contain DNA possessing genes borrowed
from unrelated species.





Pest-resistance
Wider tolerance levels
Increased growth
Herbicide resistance
Dietary supplements or oral vaccines
Genetic Engineering

70% of all processed foods in NA contain transgenic
products.

75% of soybeans, 33% of corn, 71% of cotton grown
in US is transgenic
GMO Salmon
GMO fish grow
faster and need
less food
Concern over possible escape from aquaculture
“Trojan gene affect” – Muir & Howard, 1999;
Howard et al. 2004
Roundup Ready Crops
Crops are modified to tolerate herbicides
Large quantities of herbicides can be sprayed
directly on fields
Concerns over spread of resistance and herbicide
residue on crops
Bt Corn
Bacillus thuringiensis (Bt) is a bacterium that makes
toxins that are lethal to beetles
Bt corn allows for reduced use of chemical insecticides
Concerns over human health effects
•
In 2001, Starlink, a Bt variety not yet approved for
human consumption was found in a variety of
foods
•
No toxin found, just the genes that code for it
•
Probably not toxic to humans, but may be an
allergen
Bt Corn
Also concerns over environmental effects
(Bt) is also
lethal to
Lepidoptera
(butterflies)
Golden Rice
Each year, more than a
million children die and
another 350,000 go blind
from the effects of
Vitamin A deficiency
Golden rice has moved genes from daffodils into the
rice to provide beta carotene
Considerable opposition to the distribution of golden
rice
Debate over GMOs

Supporters argue:




Improved yield with fewer insecticides
Reduced hunger
Increased health and nutrition
Critics argue:


Increased use of herbicides
What we don’t know now can hurt us later


Future environmental problems
Future human health problems
Questions for Discussion
1) Have you ever been concerned about where
your food comes from? Are you now?
2) Do you regularly wash fresh produce?
3) What would it take for you to:
1) Go to a farmer’s market regularly?
2) Buy organic produce?
3) Buy organic meat or go vegetarian/flexitarian?
4) How do you feel about eating GM foods?
What is “Good” Soil
“Good” soils: drainage, aeration, organic
matter
• 45% minerals
• 25% air
• 25% water
• 5% organic material
Soil Erosion

Erosion—Wearing away and transportation of
soil by wind, water, or ice.



Causes loss of farmable land or loss of productivity
leads to increased use of fertilizers and pesticides
Made worse by deforestation, desertification and
poor agricultural practices
Mechanisms of Erosion

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
Land Degradation

Estimated nearly 3 million ha of cropland
ruined annually via erosion, 4 million ha
transformed into deserts, and 8 million ha
converted to non-agricultural uses.
Worldwide, erosion reduces crop
production by equivalent of 1% of
world cropland per year.

Dust Bowl
1930s – extreme
drought conditions
over 65% of
continental US
Wind erosion
destroyed millions
of acres of
farmland
Sediments from lakes suggest that historically,
droughts were more frequent and more intense
How to protect against erosion?
1)
Provide Ground Cover

Annual row crops cause
highest rates of erosion
because they leave soil
bare for much of the
year.

Allow vegetation
between rows

Leave crop residue
after harvest.

Plant cover crops after
harvest.
How to protect against erosion?
2) Plant wind breaks
around fields
3) Protect necessary
waterways in field
How to protect against erosion?
4) Contour Farming — Tilling at right angles
to the slope of the land.
Each ridge acts
as a small dam
Useful on
gentle slopes
How to protect against erosion?
5) Strip Farming—Alternating strips of
closely sown crops (wheat or hay) with
row crops (corn, soy, etc.) to slow water
flow.
How to protect against erosion?
6) Terracing—Level areas constructed at
right angles to the slope to retain water.
Useful on
very steep
slopes
Points to Know
1)
What is alternative agriculture “alternative” to? Name 4 methods
discussed in lecture.
2)
How does reproduction disruption help control insect pests?
3)
What does selective breeding of crops/livestock do? How long has it
been going on?
4)
In what way is genetic modification via transgenetics (GMOs) different
than traditional selective breeding?
5)
What is the “trojan gene affect” and why could this be a big problem
for GMOs?
6)
What do the supporters and critics of GMOs argue?
7)
What is erosion? Why should humans worry about it?
8)
What are 6 farming methods to protect against wind and water
erosion?