1. The growing of food: Effects on the food, Effects on the environment
“Unit 2: Agriculture”
The growing of food:
Effects on the food,
Effects on the environment

2. Today: “Dirt” Why do we care about dirt in a class about nutrition?
“The quality of soil determines the quality and nutrients of plants.”
We could grow the same apple tree in two different areas, and they could be very different, nutritionally.

3. “Fertile Soil” “= soil that can support growth of healthy plants”
If the soil is not fertile, very little will grow/plants will not be healthy or nutritious.

4. “Plant roots grow in topsoil = surface layer of soil.”
Why would this be the most fertile layer?

5. “Topsoil
“living organisms”
“rock particles”
“water”
“air”
“organic matter (dead orgs)”
It’s the dead and decaying organisms that make the top layer the best!

6. How does soil form?
“Soil forms when rock is broken down into smaller fragments by:”
“wind”
“water”
“chemical weathering”
This is when elements in rock react with water or air.

7. Who lives there? “Insects, bacteria, algae, fungi, earthworms”
All of these help to break down dead organisms, returning their nutrients to the soil.

8. Important Point!! There is a set amount of each nutrient on Earth!
Nature MUST recycle these nutrients by breaking them down!
Organic material (apple cores) in garbage bags at the dump will NOT be returned to the ground anytime soon.

9. So what does this mean for a farmer?
“Only 10% of Earth is arable land”
“=can be used to grow crops”
Why are other areas not arable?

10. “Agriculture” “Basic processes:”
“plowing, fertilization, irrigation, pest control”
How these are carried out depends on the farmer…are they traditional or modern?

11. “Traditional” “Plows pushed by farmer or pulled by livestock.”
What does plowing do?
Mixes soil nutrients, loosens soil, uproots weeds.

12. “Organic fertilizers (manure or compost) used to enrich the soil”
Bacteria in gut of cow breaks down cow’s food into nutrients…
“Weeds removed by hand”
“Fields irrigated with ditches”
These have been used for centuries.

13. “Modern”
“Machinery (using fossil fuels) plows and harvests”

14. “Chemical fertilizers to enrich soil”
“Sprinklers/drip systems to water”
“Chemicals to kill pests”

15. There are other differences, too..
“Cropland used to lie fallow”
“=let field rest and recover for a year or two”
This would allow the decomposers time to break down old vegetation, and re-enrich the soil.

16. “Overfarming and overgrazing lead to land degradation.”
“=soil can no longer support the ecosystem.”
It is no longer fertile, and can no longer support crops (or grazers)

17. Example: Sahel region, northern Africa
Too many crops are planted too frequently
Land has fewer plants to hold topsoil in place.
What do we call it when topsoil washes away?

18. “Erosion: When fertile soil washes away, no longer held by roots”
Just like erosion of beaches, when dune grass is gone.

19. What happens to the field?
“Fields become more desertlike = desertification.”

20. “Soil Conservation” So what can be done to maintain fertile land?
“Build soil-retaining terraces”

21. “Leave strips of wild vegetation to prevent erosion”

22. In traditional farming, after a crop is harvested, the soil is plowed to bury the remains.
“No-till farming: remains of last year’s crop are left to hold soil and new seeds”

23. “Enriching the Soil” “Traditional: add manure, compost”
Nutrients go back into soil, are absorbed by plants
“More nutrients in soil, more nutrients in food”

24. “Modern: chemical fertilizers”

25. …and of course, any chemical fertilizer or pesticide added to soil is also on your food!