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Agriculture and Nutrient Cycles

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Agriculture and Nutrient Cycles Chapter 2.7 – PowerPoint PPT presentation

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Title: Agriculture and Nutrient Cycles


1
Agriculture and Nutrient Cycles
  • Chapter 2.7

2
Agriculture and Nutrient Cycles
  • The seeds, leaves, flowers and fruits of plants
    all contain valuable nutrients.
  • As crops are harvested, the valuable nutrients
    are removed from the soil.
  • This diversion of nitrates and phosphate from the
    local cycles would soon deplete the soil unless
    the farmer replaced the missing nutrients.

3
  • There are many other elements/nutrients that
    plants need, other than carbon.
  • Plants also need nitrogen (N), phosphorus (P),
    and potassium (K)
  • As plants grow, they remove these nutrients from
    the soil.
  • FERTILIZERS are materials used to restore soil
    nutrients and increase production from land.

4
  • However, adding too much fertilizer is not always
    better. Extra, unused fertilizer can end up in
    streams and lakes.

5
Fertilizer and Ecosystems
  • Read the first paragraph of Fertilizer and
    ecosystems on page 70 (10 minutes)
  • Question
  • What can happen to organisms when too much
    fertilizer is used?
  • Answer
  • Nutrients allow algae to grow rapidly
    (algal bloom)
  • Algae use oxygen
  • Algae die
  • Bacteria uses oxygen
  • oxygen levels drop
  • fish / other animals die
  • decomposer eat
  • bacteria population grows
  • use more oxygen.

6
Questions
  • Answer questions Page 71
  • 2,4,5

7
SOLUTIONS TO QUESTIONS
  • Q2 Explain how excess fertilizers might affect
    decomposing organisms.
  • ANSWER
  • Excess fertilizer can seep into waterways and
    cause the growth of algae. When the algae die,
    the population of decomposers increases rapidly,
    causing oxygen depletion in the water.

8
SOLUTIONS TO QUESTIONS
  • Q4 What dangers do high levels of nitrates in
    the drinking water present for infants?
  • ANSWER
  • Their stomachs are not as acidic as those of
    adults. Bacteria that convert nitrates to
    nitrites in the intestines can enter infants
    less acidic stomachs. The nitrites can enter the
    blood stream and bind to the hemoglobin.

9
SOLUTIONS TO QUESTIONS
  • Q5 Explain why not planting a crop and then
    ploughing in the fall might help a farmer restore
    nitrogen and phosphorus levels in the soil.
  • ANSWER
  • During the year nutrients, including nitrogen and
    phosphorous, accumulate in the plants that grow.
    If the farmer ploughs these plants under in the
    fall, the nutrients will help enrich the soil.
    This is called green manure.

10
PESTICIDES
  • CHAPTER 2.2 ( Case Study )
  • Scan figure 4

11
THINGS TO DO
  • Read Chapter 2.2
  • Page 52-57
  • Fill in the worksheet
  • 40 MINUTES TO COMPLETE
  • Check answers before the end of class

12
ANSWERS TO WORKSHEET
  • QUESTION 1 Define the following
  • A) Pest is an organism that people consider
    harmful or inconvenient
  • Examples
  • Weeds, insects, fungi, and rodents
  • B) Pesticide chemicals designed to kill pests
  • Examples Raid , DDT

13
  • QUESTION 2 Complete the table on the advantages
    and disadvantages of pesticide use

Advantages Disadvantages
Controls unwanted populations Pollution (Air and Water)
Increases Food Yields Bioamplification
Prevent diseases Ecosystem Decline (alternates)
Toxic on body
Bugs become resistance
14
  • QUESTION 3 What is the main difference between
    first generation and second generation
    pesticides?
  • 1st Generation natural chemicals
  • (Metallic based, ex. Lead, mercury and
    arsenic)
  • Not only did they kill insects, they were highly
    poisonous for people.
  • 2nd Generation made in Laboratory
  • DDT is a potent insecticide made in 1874.
  • At the time it was made people did not know its
    harmful effects
  • (Effects carcinogenic, thinning of egg shells,
    birth defects, etc.)
  • Extra
  • 2.3 million tonnes of DDT was used/year (peak
    usage was in 1962)
  • Today, there are 500 registered insecticides used
    in Canada
  • 75 of the banned insecticides are still used in
    3rd World Countries

15
Extra Place in Notes
  • 3rd Generation Modern Day Pesticides Water
    Soluble
  • Because they are water soluble they will not stay
    in the body
  • They can be excreted through sweat and urine and
    are easily broken down in the soil.
  • Problems need to be reapplied frequently because
    they break down so quickly, they are only
    effective for short periods of time, cost for
    reapplication.

16
  • QUESTION 4 Complete the table on the types of
    pesticides

Type of Pesticide Target Persistence
Insecticide Insects 2-15 years
Herbicide Weeds Days to Weeks
Fungicide Fungi/Moulds Few Days
Bactericide Bacteria Few Days
Rodenticide Rodents Few Days
17
  • QUESTION 5 Clearly explain BIOAMPLIFICATION
  • Is the increasing concentration of a toxin, in
    the fatty tissue, as organisms consume each
    other.
  • Second generation (early pesticides) were
    fat-soluble which means they would stay in the
    body. For example If a grassland ecosystem was
    sprayed with DDT, the fat-soluble pesticides
    would stay in the herbivores body, and the
    carnivores body, etc As the chemical accumulates
    so does the toxic effect.

18
  • QUESTION 5 B) Provide an example of how
    Bioamplification occurs
  • The concentration of fat-soluble pesticide
    increases as you move up the food chain.
  • Page 54, Figure 4 provides a good example
  • 1 part per Grasshopper 4 part per
    Shrew 12 parts per Owl

19
  • QUESTION 5 C) What can be done to prevent
    Bioamplification?
  • Make pesticides that do not stay in the fat
    tissue
  • Make pesticides that can be extracted from your
    body thru urination.

20
6. Clearly explain how pest become resistant to
pesticides.
  • Pests that arent affected by pesticides and are
    adapted to live even if they come in contact with
    a pesticide. They reproduce and their offspring
    are resistant as well.

21
  • QUESTION 6 Reflect and Answer Parts L-P on
    pages 56-57
  • L) Spruce budworms have become resistant to the
    pesticides available. If all of the pests are
    not wiped out in the first wave, the survivors
    can multiply in number.
  • M) Concentrations of pesticide sufficiently high
    to kill all the spruce budworms would also kill
    many other species, beneficial as well as
    harmful, insects as well as other organisms.

22
  • N) The loggers and lumber and paper-mill workers
    have benefited from the New Brunswick spraying
    program.
  • O) The loggers, lumber and paper-mill workers,
    and First Nations peoples depending on the
    forests for a livelihood, might have lost out as
    a result of the decision not to spray on Cape
    Breton Island.

23
  • P) Not spraying on Cape Breton Island has allowed
    the ecosystem to adjust and naturally recover
    from the spruce budworm infestation.
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