1. Announcements – Nov. 8, 2004

2. 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?

3. Review Chemical fertilizers Chemical pesticides 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

4. Alternative Agriculture
Crop rotation
Sustainable agriculture
Organic agriculture
Integrated pest management

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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.

11. 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

12. 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

13. 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

14. 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

15. 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

16. Bt Corn Also concerns over environmental effects
(Bt) is also lethal to Lepidoptera (butterflies)

17. 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

18. Debate over GMOs Supporters argue: Critics 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

19. Questions for Discussion
Have you ever been concerned about where your food comes from? Are you now?
Do you regularly wash fresh produce?
What would it take for you to:
Go to a farmer’s market regularly?
Buy organic produce?
Buy organic meat or go vegetarian/flexitarian?
How do you feel about eating GM foods?

20. What is “Good” Soil 25% air 25% water 5% organic material
“Good” soils: drainage, aeration, organic matter
45% minerals
25% air
25% water
5% organic material

21. 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

22. 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

23. 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.

24. 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

25. How to protect against erosion?
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.

26. How to protect against erosion?
Plant wind breaks around fields
Protect necessary waterways in field

27. How to protect against erosion?
Contour Farming — Tilling at right angles to the slope of the land.
Each ridge acts as a small dam
Useful on gentle slopes

28. How to protect against erosion?
Strip Farming—Alternating strips of closely sown crops (wheat or hay) with row crops (corn, soy, etc.) to slow water flow.

29. How to protect against erosion?
Terracing—Level areas constructed at right angles to the slope to retain water.
Useful on very steep slopes

30. Points to Know
What is alternative agriculture “alternative” to? Name 4 methods discussed in lecture.
How does reproduction disruption help control insect pests?
What does selective breeding of crops/livestock do? How long has it been going on?
In what way is genetic modification via transgenetics (GMOs) different than traditional selective breeding?
What is the “trojan gene affect” and why could this be a big problem for GMOs?
What do the supporters and critics of GMOs argue?
What is erosion? Why should humans worry about it?
What are 6 farming methods to protect against wind and water erosion?