Announcements – Nov. 8, 2004

Lecture Objectives:

Agriculture III

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 CornBacillus 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

(Bt) is also lethal to Lepidoptera (butterflies)

Also concerns over environmental effects

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 Bowl1930s – 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 Know1) 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?