Study guide for Food Systems Exam
Friday, February 10th, 2012
1. Fill in the chart for the different soil types:
Soil type
Clay
Silt
Sand
Gravel
Particle size (in mm)
Below 0.002mm
0.002-0.05mm
0.05-2.0mm
2.0-75mm
Permeability (water
holding capacity): put in
order 1-5, 1= holds the
least water/most
permeable, 5= holds the
most water/least
permeable
4
3
2
1
Porosity (% of space
between particles): put
in order 1-5, 1= most
porosity/most space
where water can travel
through, 5= least
porous/least space that
water can travel
through
4
3
2
1
2. Look at the soil types/textures of soil triangle. Which soil type holds the most water?
Clay holds the most water.
3. What is a limiting factor, and how did Liebig explain how limiting factors effect crop yield
(amount of crops produced)?
Limiting factor?
Liebig’s Law?
A limiting factor is a nutrient that there is the
Liebig’s law is the idea that some
least of present, so it limits the number of
single factor determines the growth
crops that can be produced, or inhibits the
and therefore the presence of a
fertility of the soil.
species.
4. Which of the following is most likely to be the most limiting factor: Nitrogen, Phosphorus,
Carbon, Oxygen, Sulfur or Hydrogen? Why?
Limiting factor? Why?
Phosphorous
Under many conditions, phosphorus forms stable insoluble
compounds, and there is NOT a common gaseous form of
phosphorous, so it cycles through ecosystems, much slower.
5. Identify where the following elements tend to build up/where they exist most frequently?
Rocks/minerals in the soil, Atmosphere (as a gas), in living things (biotic organisms)
Nitrogen
Phosphorus
Carbon
Atmosphere as Nitrogen (N2)
Rocks /minerals in the soil.
In living things, like forest
gas
trees.
6. Macronutrients like Nitrogen, phosphorus and potassium are added to plants in inorganic
fertilizers. Carbon is also a macronutrient. Why is carbon not included in fertilizers?
Because it can be taken in during photosynthesis in the form of CO2, from the air.
7. List two ways that humans affect the nitrogen cycle, using industrial agricultural practices?
1. Removing nitrogen form the soil, by removing the topsoil (the most nutrient rich layer of
soil)
2. Agricultural runoff caused by synthetic inorganic fertilizers.
8. Label the different soil horizons, and write what each one is composed of.
Horizon
Composition (soil
types that make it
up)
O
Humus (dead
organic matter)
A
Topsoil:
decomposed
humus+minerals
Eluviation/leaching:
sand and silt
Subsoil: Clay and
mineral deposits
O Horizon
A Horizon
E Horizon
B Horizon
C Horizon
E
B
R Horizon
C
9. A farmer wants to use a biological control to control soybean aphids, instead of using pesticide.
What are 2 biological control options for this organic farmer?
1. Predation: Ladybugs and lacewings eat soybean aphids
2. Naturally occurring plant derivatives: chrysanthemum oil can be used to repel soy bean
aphids.
10. An inorganic farmer has been using a synthetic pesticide on his crops. He uses an insecticide
that works at first, but then stops work. What is the most likely reason that the insecticide
stops working?
Pests like insects and weeds build up a resistance to pesticides, by
11. What is Integrated Pest management? (Pest management notes)
A combination of chemical, biological and physical controls selected through research on
controls or specific crops to manage pests.
12. What are 2 causes of increased Salinization in soil?
1. Over irrigation of crops (water contains ions which naturally form salt, like Na+ )
2. Monoculture/using only one crop which sucks the nutrients out of the soil repeatedly.
13. List at least 3 disadvantages and 3 advantages to using a genetically modified monoculture, like
corn?
Advantages
Disadvantages
1.Higher crop yields
1. Decreases biodiversity
2. Can use pesticides across entire field, which 2. Increases the rate at which pests build up a
are less expensive.
resistance to pesticides.
3.Less labor intensive
3. Can harm beneficial insects
14. List 5 advantages and 5 disadvantages to local, organic farming?
Advantages
Disadvantages
1. More nutrition (higher mineral content)
1. requires more labor/higher labor costs
2. No poisonous chemicals/pesticides sprayed 2. Sometimes lower crop yields
on plants (ingested)
3. Can’t use genetically modified crops, which
3. maintains soil health
can be engineered to be herbicide resistant
4. minimizes pest resistance
4. Requires more skilled labor and knowledge.
5. If available, organic fertilizers and biological 5. Takes more time for crops to grow
controls can be cheaper/free
naturally than with synthetic inorganic
6.Tend to be more drought resistant (because fertilizers
of soil health)
7. Less likely to cause runoff because natural
phosphates and nitrogen compounds are not
as soluble in water.
8. Will not pollute water with synthetic
pesticides
15. Industrial farms often use monoculture farming, so they can produce large crop yields.
Unfortunately, a lot industrial farming practices lead to soil salinization (increasing the
concentration of salt, usually by reducing the concentration of water and other solutes, like
nutrients), desertification (drying out soil, like a desert), soil erosion (carrying away soil by wind
or water). List 4 practices that are common/necessary for an industrial monoculture farm.
1. Spraying synthetic pesticides
2. Using genetically modified crops
3. Seasonal soil tilling (over turning the soil)
16. What are 3 ways to reduce soil erosion (soil composition notes 2)?
1. Terracing
2. No till agriculture
3. Agroforestry
Other options: don’t overgraze rangelands,
17. What is the green revolution, and how did affect agriculture?
The green revolution is…1) monocultures + genetically modified, high yield crops 2) increase in
irrigation, increase in synthetic pesticides and fertilizers 3) multiple crops on the same land per
year (all year)
The green revolution affected agriculture by…
Producing new strains (genetically engineered) of crops with higher yields. It led to the
industrial agriculture business we have today.
It increased per capita food production at first, increased health insurance bills and increased
percent of income on food in developing countries.
18. What is crop rotation? Describe how it relates to the nitrogen cycle.
Crop rotation is…changing crops on land by season, usually to preserve the soil health
It relates to the nitrogen cycle because…
Nitrogen fixation in the root systems of legume plants can increase fixed nitrogen in the soil
that the next crop can easily uptake. It basically fertilizes the soil naturally!
19. List 3 advantages and disadvantages of using genetically diverse plants (with different DNA)?
Advantages
Disadvantages
1.increase plants’ resistance to pests
1. Usually requires more initial costs.
2. Requires more knowledge/skill and
2.increase soil health, planting in plants that
labor
help eachother/ go together (attract
3. Produces lower crop yields of a single
beneficial insects for other plants, fix
type of crop
nitrogen…etc)
3.allows for adaptation to different growing
seasons.
20. In the globally, of the world uses 65% of its freshwater use on agriculture. The U.S. is slightly
lower. Calculate the percent of freshwater used in the U.S. for irrigation and livestock use by
using the diagram below.
What is the total (ground water +
surface water) used on livestock
in the U.S.?
What is the total (ground water +
surface water) used on Irrigation
in the U.S.?
What is the total freshwater used
in the U.S?
What is the percentage of
freshwater used for irrigation and
livestock in the U.S.?
2500+1000=3,500 million gallons per day
89,500 + 57,000 = 146,500 million gallons per day
216 ,000+84,000= 300,000 million gallons per day
146,500/300,000 = 48.8% = about 50%
21. What are 3 results of overusing groundwater?
1. Salt water intrusion
2. Land subsidence at underground wells
3. Desertification and Saliniztion
22. What are 4 ways to conserve water/reduce your ecological footprint for water through
irrigation practices?
1.Irrigate only at night
2.Irrigate with treated urban waste water
3.cover irrigation ditches to prevent evaporation
4.Avoid growing water thirsty crops (that do not due well in dry climates).
23. What is Eutrophication? How does fertilizer run off cause Eutrophication?
Eutrophication is…
(list the steps)
1) Nitrates and phosphates cause nutrient enrichment in the water, which increase algal
blooms and surface plants.
2) Ground plants underwater die and decompose, which increase the biochemical
demand for oxygen (BOD)
3) Cover irrigation ditches to prevent evaporation.
4) Avoid growing water thirsty crops in dry areas.
Fertilizer run off causes Eutrophication by...
Increasing algal blooms, algae die off and decrease dissolved oxygen levels in water.
24. What is BOD? How are BOD and dissolved oxygen levels related? How is dissolved oxygen
levels related to ecosystem health?
BOD is….Biochemical oxygen demand
As BOD increases due to sewage or agricultural runoff, dissolved oxygen…decreases
Dissolved oxygen affects organisms in an aquatic ecosystem because…
Many organisms, like fish need the dissolved oxygen to breathe. They utilize oxygen in the
water as it passes through their gills.
25. What is a subsistence farm? Fill in the diagram for a subsistence farm.
Subsistence farming is…farming to feed/sustain just one’s self and family.
26. Explain 3 practices that a subsistence farmer might have to implement in a farm in subsistence
farm in Korea, which has monsoon rains in June and July, and temperatures of 0-10° Celsius in
the winter and can get up to 33°C in the summer. Consider how they could adjust to the local
environment.
Farming Practice
How it will help sustain the farm?
1.Terracing
Reduces soil erosion along mountain sides
2.crop rotation
Maintains fertility of soil
3.cultivation of proper Selecting crops for the proper weather conditions will reduce the
crops
need to over water or drain the deplete the soil of nutrients.
27. What are 3 soil conservation practices that could be used on a farm in Teagu , Korea (which has
distinct wet and dry seasons)?
Conservation practices How it will help sustain the farm?
1.Terracing
2.Crop rotation
3.Not over irrigating
28. List 3 advantages and disadvantages to polyculture subsistence farming.
Advantages
Disadvanatages
1. Less soil erosion
1. labor intensive
Better irrigation
2. lower crop yields
2. decrease in chemicals and GMO’s
3. decrease in profit margins.
increase in pest resistance
3. increase in diversity
29. Why is it more efficient (energy and land use wise) to produce grain and produce (crops) for
human consumption than meat for human consumption?
Land use : meat= more land and also need to grow plants to feed the cows
Energy use: Energy lost from waste production and respiration (by animals and decomposers)
Energy reuired to store feed grains, management and labor required for animal waste and care,
plants are primary producers tend to be more efficient when use of sunlight.