National Agricultural Literacy Curriculum Matrix
Fertilizers and the Environment (Grades 6-8)
6 - 8
1 class period
In this lesson students will recognize that fertile soil is a limited resource to produce food for a growing population, describe the role fertilizer plays to increase food productivity, distinguish between organic and commercial fertilizers, and recognize how excess nutrients are harmful to the environment.
- 1 apple
- 1 knife
- Master 5.1, Newspaper Articles (Prepare an overhead transparency.)
- Master 5.2, Population and Land Use Graphs (Make 1 copy for each group of 3 students.)
- Master 5.3, Needs of the Future (Make 1 copy for each group of 3 students.)
- Master 5.4, Thinking about Fertilizers (Make 1 copy for each group of 3 students.*)
- Master 5.5, Pros and Cons of Different Fertilizers (Make 1 copy for each group of 3 students.)
- Master 5.6, Nutrient Pollution (Make 1 copy for each group of 3 students.*)
- Master 5.7, Nutrient Pollution Discussion Questions (Make 1 copy for each group of 3 students.*)
* Half of the groups receive Masters 5.4, Thinking about Fertilizers and 5.5 Pros and Cons of Different Fertilizers, and the other half receive Masters 5.6, Nutrient Pollution and 5.7, Nutrient Pollution Discussion Questions.
Essential Files (maps, charts, pictures, or documents)
non point source: nutrient pollution that enters the air, surface water, ground water, and the oceans from widespread and distant activities. Examples of non point sources are farms and cities. Because it comes from a number of different sources, a non point source is much harder to trace and quantify than a point source of nutrient pollution.
nutrient pollution: the presence of excessive amounts of nutrients such as nitrogen and phosphorus in surface water, groundwater, air, and non-agricultural land. In surface waters, these nutrients stimulate the growth of algae and phytoplankton,which eventually depletes the waters of oxygen and impacts many aquatic organisms.
nutrient toxicity: the presence of an excessive amount of a specific nutrient, which is harmful to the organism
point source: nutrient pollution that comes from a specific source that can be identified such as a factory or a wastewater treatment plant
Background Agricultural Connections
Interest Approach – Engagement
- Ask your students if they think we have adequate land to grow and produce enough food for a growing population. Can every acre of farm land be used to grow food crops or raise animals? Students may picture areas where there is a lot of open space. However, do they realize that not all land is suitable for growing crops?
- After completing this lesson, students will be able to:
- 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, and
- identify different sources of nutrient pollution.
Activity 1: The Big Apple
Tip from the field test: This activity uses an apple as a model of Earth. Students discuss the various ways people use land and make predictions about what percentage of Earth’s land is needed to grow our food. After discussing the ways in which land is used (Step 2), you may consider having the students create their own pie charts where they predict the percentages associated with different land uses, especially farming. Later, their predictions can be compared with the actual values revealed by the apple demonstration.
- Explain to the class that this activity is concerned with how we as a society use land. The amount of land on Earth stays the same, so as the world’s population gets larger, it becomes even more important that we make wise decisions about how it is used.
- Explain that land is used for many different reasons. Ask, “What are some of the most important uses for land?” Write students’ responses on the board or an overhead transparency. Students’ responses may include the following:
- Industries or places where we work
- Pastures or land for livestock.
- Parks, sports, and recreation.
- Wildlife habitat (wetlands,mountain ranges, forests, deserts, beaches, and tundra).
- If one of these uses is not mentioned by a student, ask guiding questions to bring it out. A student may point out that some land such as a desert has no use. Of course, any land that is not being used by humans can be considered a habitat for wildlife and provides a variety of other economic services for people. For example, wetlands help remove nutrient pollution from rivers, lakes and estuaries.
- Call attention to the apple and the knife. Explain that the apple represents Earth. Ask, “How much of the total Earth’s surface do you think is devoted to farming?” Students’ responses will vary. Some may remember that about 70 percent of the surface is water.
- Use the knife to cut the apple into 4 equal parts. Set 3 parts aside and hold up 1 part. Explain that the surface of the world is about 70 percent water, so this 1 piece represents that part of the surface that is land. Remind students of the many different uses for this relatively small amount of land.
- Use the knife to cut the 1/4 piece of apple in half 3 more times, each time discarding 1/2. Finally, hold up 1 of the smallest pieces and explain that it represents 1/32 of the surface of Earth or 1/8 the land where we live. This is the amount of land available for farming. Point out that the skin on this small piece of apple represents the tiny layer of topsoil that we depend on to grow food.
- Explain that because we put land to so many different uses, the amount devoted to farming has hardly changed during the past 50 years. Scientists are worried about how we will feed the world’s growing population in the next 50 years.
Activity 2: Using Land Wisely
- Display a transparency of Master 5.1, Newspaper Articles and cover the bottom portion so that only the top article can be read. Ask for a student volunteer to read the article aloud.
- Explain to students that they will continue in their roles as agricultural experts concerned with increasing crop yields on farms. Ask students to summarize the content of the article.
- Try to focus the discussion on the world. Most students in the United States do not have direct experience with severe hunger. Help them understand that in addition to human suffering, hunger can also lead to political instability. It is in everyone’s best interest to eliminate world hunger. The article mentions that population growth contributes to the problem of world hunger. Although population growth is an important societal issue, please remind students that the scope of this module is limited to discussions related to agricultural practices. The article also mentions the availability of freshwater and increasing temperatures due to global warming as challenges for growing more food. If they don’t understand why increasing temperatures cause lower crop yields, explain that it takes more energy and water for plants (and people) to maintain themselves at higher temperatures. Using humans as an example, you can point out that marathon records are usually set at cooler temperatures.
- Now uncover the bottom article and ask for a second volunteer to read it aloud.
- Once again, ask students to summarize the article. Students should recognize that there are many factors that influence world hunger and that addressing the problem requires the skills of many different types of people including as social scientists, climatologists, ecologists, water management experts, and agricultural experts.
- Divide the class into groups of 3 students. Explain that their first task is to investigate how land use is expected to affect farming in the future.
- Pass out to each group a copy of Master 5.2, Population and Land Use Graphs and Master 5.3, Needs of the Future. Instruct groups to use the graphs on Master 5.2, Population and Land Use Graphs to help them perform a calculation on Master 5.3, Needs of the Future about how much farmland will be needed in the year 2050. Give groups 5 to 10 minutes to perform their calculations.
- The numbers needed to perform the calculation are indicated on the population graph.
- For an explanation of calculations, see Teacher's Note
- Ask each group to report the results of their calculations. Write their answers on the board or on an overhead transparency.
- If any answers are out of the expected range, go through the calculation step by step, identify the mistake, and correct it.
- Review the land use for the class. If crop yields stay the same over the next 50 years, then an extra 10 billion acres of farmland will need to be set aside and cultivated.
- Ask the students to remember the different uses of land that they described in Activity 1: The Big Apple, Step 2. Point to the list of land uses on the board or display the transparency where they are listed.
- Ask, “If billions of acres of extra farmland are needed to feed people, where should it come from?” “What are you willing to sacrifice?”
- Students likely will believe that people must have adequate land for the places where they live and work. They may suggest taking the land from parks or wildlife habitats. Some may suggest that if more people became vegetarians, the extra farmland could come from pastures where livestock graze. These questions are not intended to settle the issue. Instead, they are intended to prompt a discussion that helps students see the scope of the problem and to consider some of the difficult decisions that may lie ahead.
- Explain that in the next activity, they will consider how farming practices can influence land use and crop yields.
Activity 3: Fertilizers and the Future
Teacher note: In this activity, students read about organic and commercial fertilizers (Master 5.4, Thinking about Fertilizers) and nutrient pollution (Master 5.6, Nutrient Pollution). In both masters, the information is a brief introduction to the topics. The information is not meant to be comprehensive. Rather, it is designed to challenge students’ critical-thinking skills.
- Remind students that in Activity 2: Using Land Wisely they calculated that 10 billion extra acres of farmland would be needed to feed the world’s population in 2050. Ask, “What assumption was made in reaching this conclusion?”
- Students’ answers will vary. Some may focus on assumptions associated with the rate of population growth. This is a good answer, but you should guide the discussion to remind students that their calculations assumed that the food yields on farms would remain the same during the next 50 years.
- Ask, “What will be the effect of increasing the amount of food that an acre of farmland can produce?”
- Students should realize that if farmland becomes more productive, then fewer acres will be required to meet the world’s food needs.
- Explain that in their roles as agricultural experts, they are going to make recommendations to the Earth Food Bank about how to farm in the future. Explain to students that when considering the proper use of fertilizer, they want to increase crop yields, while at the same time minimizing harm to the environment. Proper application of fertilizer means the following:
- Fertilizer is added at the right time. Fertilizers should be applied during that part of the plant’s life cycle when the nutrients are needed.
- Fertilizer is added at the right place. Fertilizers should be applied in a location where the nutrients can be taken up by the plant’s root system. This can also mean not adding fertilizer to land that is too close to waterways.
- Fertilizer is added at the right rate. Fertilizers should be applied at the rate at which the plant can use the nutrients.
- Explain that students need to learn more about fertilizers and their effects on the environment.
- Pass out to half of the groups a copy of Master 5.4, Thinking about Fertilizers and a copy of Master 5.5, Pros and Cons of Different Fertilizers.
- Pass out to the other groups a copy of Master 5.6, Nutrient Pollution and a copy of Master 5.7, Nutrient Pollution Discussion Questions.
- Instruct the groups to read the information found on the first handout (either Master 5.4, Thinking about Fertilizers or Master 5.6, Nutrient Pollution) and to discuss within their groups their understanding. Students should relate the ideas of “right time, right place, and right rate” when considering the use of fertilizers and their impacts on the environment.
- Students should use the second handout (either Master 5.5, Pros and Cons of Different Fertilizers or Master 5.7, Nutrient Pollution Discussion Questions) to record their conclusions.
- Students reading about fertilizers should be able to identify three or four advantages and disadvantages of each type of fertilizer. Students reading about nutrient pollution should be able to describe how excess nutrients can produce algal blooms that use up oxygen in the water, leading to suffocation of other plants and animals. They should be able to identify wastewater treatment facilities and industrial plants as point sources of nutrient pollution. They should identify agriculture, urban development, septic systems, and the burning of fossil fuels as non point sources of nutrient pollution. Student suggestions for limiting non point sources of nutrient pollution will vary. There is no simple correct answer. Look for logical responses that students can defend using evidence. The idea is to get them thinking about the multiple sources of nutrient pollution and for them to realize that limiting its effects will require a complex set of regulations, incentives, and government oversight.
- After the groups have completed their tasks, ask for volunteers to read their conclusions.
- Make a list of the advantages and disadvantages of each type of fertilizer on the board or on an overhead transparency.
- Discuss answers to the questions about nutrient pollution.
- Ask, “Why do think that some farmers use organic fertilizers and others use commercial fertilizers?"
- Student responses will vary. Try to bring out in the discussion that the farmers in the United States have more options than farmers in poorer countries, who may have no choice and must use organic fertilizers that they produce for themselves. A consequence is that farmers in poorer countries obtain lower crop yields as compared with farmers in the United States. However, farmers in the United States often choose to use organic fertilizers for a variety of other reasons.
Teacher note: Try to avoid getting bogged down in debating whether or not food that is organically grown is safer or tastes better than food grown using commercial fertilizers. This is not the focus of the lesson. Scientific studies have not been able to consistently find taste, health, or safety differences between food grown using the two types of fertilizers.
Concept Elaboration and Evaluation
After conducting these activities, review and summarize the following key concepts:
- Fertile soil with an adequate climate for plant growth is a limited resource.
- Soil and water are natural resources that need to be managed and conserved.
- The use of various fertilizers needs to be used correctly to avoid negative environmental impacts.
Optional Homework Assignment 1 Instruct students to research andwrite a short paper describing the advantages and disadvantages of organic and commercial fertilizers. For each type of fertilizer, students should include information about the fertilizer’s composition, the fertilizer’s application, its influence on crops yields, its impacts on the environment, and its role in agriculture, both in North America and globally.
This lesson is the last in a series of five related lessons. Refer to the following lessons for further depth.
Optional Homework Assignment 2 Instruct students to involve their parents or guardians in this activity. Using the world population graph on Master 5.2, Population and Land Use Graphs, ask students to determine the world’s population when their parents or guardians were their age. Have students calculate the population increase from then until now. Have students ask their parents or guardians: o “What is the world’s population today?” o “How much of Earth is used for farmland?” Have students,with their parents or guardians, come up with 3 ways of increasing the world’s food supply. Instruct students to turn in a summary of the activity. It should contain o the world’s population when the parents or guardians were the same age as the student, o the calculation showing the increase in population between then and now, o the parents’ or guardians’ answers to the population and farmland questions, o the 3 proposed ways of increasing the world’s food supply, and o the parents’ or guardians’ signatures.
Suggested Companion Resources
- Topsoil Tour (Kit)
- Apple as Planet Earth video (Multimedia)
- Phosphate Mining Video (Multimedia)
- Potash Mining Video (Multimedia)
- #SoilScience Reader (Booklets & Readers)
- From the Ground Up: The Science of Soil (Website)
- Unlock the Secrets in the Soil (Website)
- Web Soil Survey (Website)
Agricultural Literacy Outcomes
Agriculture and the Environment
- Describe benefits and challenges of using conservation practices for natural resources (e.g., soil, water, and forests), in agricultural systems which impact water, air, and soil quality (T1.6-8.b)
- Discover how natural resources are used and conserved in agriculture (e.g., soil conservation, water conservation, water quality, and air quality) (T1.6-8.c)
- Discuss (from multiple perspectives) land and water use by various groups (i.e., ranchers, farmers, hunters, miners, recreational users, government, etc.), and how each use carries a specific set of benefits and consequences that affect people and the environment (T1.6-8.d)
- Recognize how climate and natural resources determine the types of crops and livestock that can be grown and raised for consumption (T1.6-8.g)
Plants and Animals for Food, Fiber & Energy
- Explain the role of ethics in the production and management of food, fiber and energy sources (T2.6-8.b)
- Identify farm practices for plant protection (e.g., using a pesticide, integrated pest management, cultural practices) and the harvest of safe products for consumers (T2.6-8.c)
Science, Technology, Engineering & Math
- Explain the harmful and beneficial impacts of various organisms related to agricultural production and processing (e.g., harmful bacteria/beneficial bacteria, harmful/beneficial insects) and the technology developed to influence these organisms (T4.6-8.f)
- Provide examples of science and technology used in agricultural systems (e.g., GPS, artificial insemination, biotechnology, soil testing, ethanol production, etc.); explain how they meet our basic needs, and detail their social, economic, and environmental impacts (T4.6-8.i)
Education Content Standards
Natural Resource Systems Career Pathway
NRS.02.02Assess the impact of human activities on the availability of natural resources.
Plant Science Systems Career Pathway
PS.01.03Develop and implement a fertilization plan for specific plants or crops.
MS-ESS3: Earth and Human Activity
MS-ESS3-3Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.
MS-ESS3-4Construct an argument supported by evidence for how increases in human population and per-capita consumption of natural resources impact Earth’s systems.
State specific Standards and Objectives
Common Core Connections
Reading: Anchor Standards
CCSS.ELA-LITERACY.CCRA.R.10Read and comprehend complex literary and informational texts independently and proficiently.
CCSS.ELA-LITERACY.CCRA.R.8Delineate and evaluate the argument and specific claims in a text, including the validity of the reasoning as well as the relevance and sufficiency of the evidence.
CCSS.ELA-LITERACY.CCRA.R.9Analyze how two or more texts address similar themes or topics in order to build knowledge or to compare the approaches the authors take.
Speaking and Listening: Anchor Standards
CCSS.ELA-LITERACY.CCRA.SL.1Prepare for and participate effectively in a range of conversations and collaborations with diverse partners, building on others’ ideas and expressing their own clearly and persuasively.
Language: Anchor Standards
CCSS.ELA-LITERACY.CCRA.L.5Demonstrate understanding of figurative language, word relationships, and nuances in word meanings.
Writing: Anchor Standards
CCSS.ELA-LITERACY.CCRA.W.4Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience.
CCSS.ELA-LITERACY.CCRA.W.9Draw evidence from literary or informational texts to support analysis, reflection, and research.