Agriculture and Nutrient Cycles Chapter 2.7

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.

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. FERTILIZERSFERTILIZERS are materials used to restore soil nutrients and increase production from land.

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

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: 1.Nutrients allow algae to grow rapidly (algal bloom) 2.Algae die 3.Bacteria decompose algae so they increase. 4.Bacteria use up all the oxygen in the water. 5.Fish / other animals die

Fertilizer and Ecosystems Q2 Why do the levels of nitrogen and phosphorus in fields decline when crops are harvested? Answer: Nitrogen and phosphorus along with water are drawn up by the roots of the plant so when crops are harvested, hence removed – these nutrients are removed with the plant.

SOLUTIONS TO QUESTIONS Q3 – 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.

SOLUTIONS TO QUESTIONS Q4 – 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.”

PESTICIDES CHAPTER 2.2 ( Case Study ) Scan figure 4

THINGS TO DO: Read Chapter 2.2 Page Fill in the worksheet 40 MINUTES TO COMPLETE Check answers before the end of class

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

QUESTION 2 – Complete the table on the advantages and disadvantages of pesticide use: AdvantagesDisadvantages Controls unwanted populations Pollution (Air and Water) Increases Food YieldsBioamplification Prevent diseasesEcosystem Decline (alternates) Toxic on body Bugs become resistance

QUESTION 3 – What is the main difference between first generation and second generation pesticides? 1 st Generation – natural chemicals (Metallic based, ex. Lead, mercury and arsenic) Not only did they kill insects, they were highly poisonous for people. 2 nd Generation – made in Laboratory DDT is a potent insecticide made in At the time it was made people did not know it’s 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 3 rd World Countries

Extra: Place in Notes 3 rd 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.

QUESTION 4 – Complete the table on the types of pesticides: Type of Pesticide TargetPersistence InsecticideInsects2-15 years HerbicideWeedsDays to Weeks FungicideFungi/MouldsFew Days BactericideBacteriaFew Days RodenticideRodentsFew Days

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.

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

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.

#6. Clearly explain how pest become resistant to pesticides. Pests that aren’t 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.

QUESTION 6 – Reflect and Answer Parts L-P on pages 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.

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.

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