HEY! Get out your objectives #4-12 for a

stamp!Update your food journal

for a stamp!Read the board!

Monoculture

Polyculture

Polyculture

Benefits:Easy to manageProvides uniformityCan be grown by few

people as long as they have large machines

Lack of diversity = potential loss of crop to disease/pest

Need for pesticidesNeed for inorganic

fertilizer because crop takes particular nutrient from soil

Loss of biodiversity from field edges/cover crops

What are the tradeoffs of monoculture?

Genetic resistance and the pesticide treadmill

Benefits:Easy to manageProvides uniformityCan be grown by few

people as long as they have large machines

Lack of diversity = potential loss of crop to disease/pest

Need for pesticidesNeed for inorganic

fertilizer because crop takes particular nutrient from soil

Loss of biodiversity from field edges/cover crops

What are the tradeoffs of monoculture?

Pests and diseases generally are plant-specific.

• Examples – • Boll weevil attacks

cotton plants• Rust fungus attacks

corn• Yellow rust fungus

attacks wheat

Each crop needs some of the same nutrients . . .

• Nitrogen• Phosphorus• Potassium• Trace elements

• But each crop takes the same nutrients out of the soil each time it’s grown.

• Example: corn uses a LOT of nitrogen

So why do monocultures require lots of fertilizer?

What IS fertilizer?

• Synthetic/Inorganic fertilizer:

• Made from natural gas (a fossil fuel)

• Examples:– Miracle Gro– Ammonium nitrate– Scott’s turf builder

• Organic fertilizer• Created from an

ecological process or organism

• Examples:– Fish emulsion– Blood meal– Bone meal– compost

Fertilizer nutrients – what do those numbers mean?

• Nitrogen• Phosphorus • Potassium

Nitrogen cycle – Why is nitrogen so important?

• Present in all proteins (structural and enzymatic) and nucleic acids (DNA and RNA)

• Nitrogen atoms cycle through the environment just like water molecules!

Remember the water cycle?

Legumes are the stars!

These are legumes, too!

Rhizobium bacteria in nodules on legume roots start the cycle

The nitrogen cycle!

Let’s sum up!

• Answer Objectives #13-16 right now!

Houston, we have a problem (and it’s linked to fertilizers!)

Eutrophication

Page 137

Eutrophication Obj #17

• Each pair/tri needs a white board, 2 markers, and an eraser – send a runner now!

• Re-read the paragraph on artificial eutrophication.

• List the steps of eutrophication on obj #17.• Compare your list with your neighbors• Use your notes to draw a cartoon of the

process on the white boards.

Plant nutrients (nitrogen and phosphorus) cause eutrophication

Other sources of plant nutrients

• Untreated sewage • Manure from livestock• Pet wastes

Hypoxic zones “Dead zones” – form in the summer Gulf of Mexico

So what can YOU do?

Eutrophication

• Which pollutants are involved?• What are the sources of these pollutants?• Are these sources point or nonpoint sources?• What are the effects of eutrophication?• Why does the dead zone form in the Gulf near

New Orleans?• Why does the dead zone form in the summer?• Why should we be worried about the dead zone?