Lesson 5: Fertilizers and the Environment

Explain-Elaborate

•Recognize that farmland is a finite resource

•Appreciate that the world’s growing population demands an increase in food productivity

•Describe the role fertilizer plays in increasing food productivity

•Distinguish between organic and commercial fertilizers

•Describe how excess nutrients are harmful to the environment

•Identify different sources of nutrient pollution

By the end of this lesson, you’ll be able to:

What we’re learning!

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Warm up:

The Earth

Warm up: What are some of the most important uses for land?

Warm up: Make a prediction

Create a pie chart predicting the percentages associated with different land uses.

Demonstration: Apple as the Earth

• Land available for farming:• 1/32 of the earth’s

surface • 1/8 of the land

where we live

• The earth’s surface is about 70% water

Arable land map

[If available, map of world agriculture]

Arable land: agricultural land under a system of crop rotation

Class Activity: Using Land Wisely

Time: 10 minutes Instructions: Use the graph and chart to complete the questions on the following slides.

World Population Growth

World Land Use

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1800 1850 1900 1950 2000 2050

(9.6)

(7.19)2013

(3.0)

(1.5)(1.0)

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Year

Part A: How much farmland is used to feed each person today?

•Step 1. Use the World Population Growth graph on the previous slide, Population and

Land Use Graphs to estimate Earth’s population right now: ____ billion people.

•Step 2. The 11 percent of land devoted to farming corresponds to 33 billion acres of

farmland.

•Step 3. Divide the 33 billion acres of farmland by the population

(from Step 1) to get the number of acres of farmland per person:

33 billion acres farmland ÷ ____ billion people = ____ acres per person

Part A: How much farmland is used to feed each person today?

•Step 1. Use the World Population Growth graph on slide 11, Population and Land Use

Graphs to estimate Earth’s population right now: 7.19 billion people.

•Step 2. The 11 percent of land devoted to farming corresponds to 33 billion acres of

farmland.

•Step 3. Divide the 33 billion acres of farmland by the population

(from Step 1) to get the number of acres of farmland per person:

33 billion acres farmland ÷ 7.19 billion people = 4.59 acres per person

Part B: How many acres of farmland per person will be available in 2050?

•Step 1. Use the World Population Growth graph on slide 11 Population and Land Use

Graphs to estimate Earth’s population in the year 2050: ____ billion people.

•Step 2. Divide the 33 billion acres of farmland by the population (from Step 1) to get the

number of acres of farmland per person:

33 billion acres farmland ÷ ____ billion people = ____ acres per person

Part B: How many acres of farmland per person will be available in 2050?

•Step 1. Use the World Population Growth graph on slide 11 Population and Land Use

Graphs to estimate Earth’s population in the year 2050: 9.6 billion people.

•Step 2. Divide the 33 billion acres of farmland by the population (from Step 1) to get the

number of acres of farmland per person:

33 billion acres farmland ÷ 9.6 billion people = 3.4 acres per person

Part C: Assuming that crop yields stay the same, how much extra land will be needed for farming in 2050?

• Step 1. Calculate the estimated population increase factor from now to 2050:

population in 2050 (from Part B) ÷ population now (from Part A) = ____

• Step 2. Multiply the 33 billion acres of farmland times the population increase factor

(from Step 1):

33 billion acres farmland x population increase factor = ____ billion acres of farmland

needed in 2050

• Step 3. To find out how much extra farmland will be needed in 2050, subtract the 33 billion acres

(today’s farmland) from the number of acres needed in 2050 (from Step 2):

____ billion acres needed in 2050 - 33 billion acres = ____ billion extra acres of farmland needed

Part C: Assuming that crop yields stay the same, how much extra land will be needed for farming in 2050?

• Step 1. Calculate the estimated population increase factor from now to 2050:

population in 2050 (from Part B) ÷ population now (from Part A) = 1.33

• Step 2. Multiply the 33 billion acres of farmland times the population increase factor

(from Step 1):

33 billion acres farmland x population increase factor = 44.06 billion acres of farmland

needed in 2050

• Step 3. To find out how much extra farmland will be needed in 2050, subtract the 33 billion acres

(today’s farmland) from the number of acres needed in 2050 (from Step 2):

44.06 billion acres needed in 2050 - 33 billion acres = 11.06 billion extra acres of farmland needed

If billions of acres of extra farmland are needed to feed people, where should

it come from? What are you willing to sacrifice?

11 billion extra acres of farmland will be needed to feed the world’s population in 2050

What will be the effect of increasing the amount of food that an acre of farmland can produce?

• Right time: apply fertilizer during the part of the plant’s life cycle when nutrients are needed.

Proper use of fertilizer:

• Right place: apply fertilizer where the plant’s root system can easily absorb it and far from waterways to minimize pollution.

• Right rate: apply fertilizer at the rate the plant can use it.

Copyright © 2013 Discovery Education. All rights reserved. Discovery Education Inc. is a subsidiary of Discovery Communications, LLC.

Your role: Agricultural expert

Video: Thinking about fertilizers

Would you rather be a farmer before the 19th century or a farmer today? Why?

How did synthetic fertilizers help farmers?

Consider:

Video: Nutrient Pollution

What is the effect of low oxygen in the water?

What causes algae? Have you ever seen algae in water?

Consider:

What is eutrophication?

Conclusions: Pros and Cons of Organic Fertilizer

Advantages Disadvantages

Organic Fertilizers

Commercial Fertilizers

Discussion Questions:

1. Why are excessive amounts of nutrients bad for the environment?

2. What is the difference between a point source and a nonpoint source of nutrient pollution? List examples of each type of source.

3. What are some ways to limit nutrient pollution from nonpoint sources?

Conclusions: Nutrient pollution

Why do some farmers use organic fertilizers while others use commercial fertilizers?

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Looking forward: The future of farming

Copyright © 2013 Discovery Education. All rights reserved. Discovery Education Inc. is a subsidiary of Discovery Communications, LLC.