The Right Diet for Your Plants
6 - 8
In this lesson, students will learn how to read a fertilizer label, understand the components of fertilizers, and explore factors for choosing the appropriate fertilizer for a given situation. Students will use their knowledge and conduct research on one type of soil supplement to design a persuasive product advertisement. Grades 6-8
Four or five, 50-minute sessions
- Packaged fertilizer labels (optional)
- Copies of What's Growin' On? Elements for Life
- How to Read a Fertilizer Label handout (1 per student)
For the class:
- 1 or 2 copies of the Advertisement Options List
- Reading #1: Why Must We Replace Nutrients Back into the Soil?
- Reading #4: Fertilizers
For each student:
- Magazines containing numerous ads
- Blank, white paper and construction paper
- Markers or colored pencils
- One Advertisement Option
- Soil Supplement Advertisement handout
Essential Files (maps, charts, pictures, or documents)
amendment: any material added to soil to make it more productive such as fertilizer or compost
compost: a mixture made of decaying organic material used to fertilize plants and amend soils
deficiency: a substance that is lacking
fertilizer: any material of natural or synthetic origin that is applied to soils or plant tissues to supply one or more nutrients essential to plant growth
green manure: vegetation that is plowed into the field to improve soil composition; normally a legume such as beans or alfalfa
manure: animal waste used for fertilizing land
Background Agricultural Connections
This lesson is part of a series called, Too Much? Too Little? created to introduce middle school students to the connection between soil nutrients and the food they eat. The lessons consist of a series of demonstrations and hands-on experiments that show that plants require nutrients in certain quantities. The lesson series allows students to investigate soil properties, learn how to properly prepare fertilizer nutrient solutions, identify deficiencies in plant nutrients using a key, and much more. Other related lessons include:
- Plant Parts and Functions: Anatomy and physiology of a plant.
- Digging Into Nutrients: How plants obtain nutrients from the soil.
- The Right Solution: How fertilizer solution is properly calculated and applied.
- Can We Have Too Much of a Good Thing?: Effects of applying too much or too little fertilizer.
- The Right Diet for Your Plants: Read fertilizer labels and choose the best fertilizer.
- Let's Vote On It: How soil nutrients effect local communities and economies.
- It's a Dirty Job: How earthworms benefit soil.
A fertilizer is any natural or manufactured material added to the soil or water to increase or replace one or more nutrients needed for plant growth. In California, all commercial fertilizers are monitored by the California Department of Food and Agriculture (CDFA) and are required to follow specific label guidelines. The three numbers on the fertilizer package are standardized and represent the percentages of nitrogen (N), phosphorus (P), and potassium (K) in that order.
Manures and commercial fertilizers are illustrated in this lesson so that students can compare and contrast two basic types of fertilizers. The issues revolving around plant nutrients are complex. Plant nutrient requirements are not a “one size fits all” situation.
Different amounts of nutrients are required for different crops, and nutrients may be taken up at different rates during various growth stages of the plant. The percentages of N, P, and K are lower in manure than in commercial inorganic fertilizers. Commercial inorganic fertilizers require mining and the use of fossil fuels for manufacturing. Commercial inorganic fertilizers are generally easier to apply than manure and composts.
Manures provide the organic matter needed to increase the water absorption and aeration of soils. Discuss with your students the importance of continuing research in the area of nutrient requirements of plants and sustainable practices that will conserve resources and produce enough food for the growing population.
Farmers and home gardeners may find that their soil is lacking in important plant nutrients. Soils can be improved in a variety of ways. A visit to your local garden center will give you an idea of just how many choices are available for improving your soil with nutrients. You might find yourself asking how to choose the best fertilizer for your garden, and may want to ask one of the garden center experts to help compare different products. In this lesson, students will research a specific soil supplement that they have been assigned. The research will provide background information for an advertisement students will design to entice consumers to purchase their product.
Advertising plays a major role in marketing new and existing products to consumers. Your students will practice what it takes to persuade someone to purchase and use a product. This lesson provides a perfect opportunity for you to lead a class discussion on supply and demand, the cost of items, and how advertising affects what people purchase. At the same time, the students will learn about the different soil supplements that can be used to grow healthy plants.
Interest Approach - Engagement
- Ask students to list some of the basic nutrients our bodies need to be healthy. Students should list examples such as protein, carbohydrates, fats, vitamins, and minerals.
- Next, ask students if there are specific periods of a person's life that they require either additional or fewer nutrients. If needed, provide examples such as an athlete, a growing teenager, or a baby.
- Summarize your discussion by helping students understand that all humans have similar nutrient requirements, but they do change slightly according to age, physical exercise, etc.
- Point out that plants also require specific nutrients, just like people. Ask if a plant's nutrient requirement changes through its lifecycle or in different locations. Yes. In this lesson students will be learning about fertilizer and how specific fertilizers can be formulated to meet the needs of various plants.
Activity 1: How to Read a Fertilizer Label
- Complete the How to Read a Fertilizer Label handout with your students. This may be done as a class, group, or individual activity.
Activity 2: It All Ads Up
- Have students look through a magazine and analyze the ads. Have students pick a favorite and a least favorite ad. Share some of the ads with the class and discuss what makes an advertisement effective.
- Make one or two copies of the Soil Supplement List. Cut list into strips, and place in hat or container. There are 20 different soil supplements on the list. Have each student pull a soil supplement description out of the hat.
- Explain to students that their assignment is to design a magazine ad for the soil supplement item they pull out of the hat.
- Review the Soil Supplement Advertisement handout directions with the class. Provide the readings Why Must We Replace Nutrients Back into the Soil? and Fertilizers. Discuss the main points of these readings with students. Explain to students that many consumers may not know that fertilizers provide plants with essential nutrients for growth. Explain that nutrients must be replaced back into the soil after they have been removed along with harvested crops. As advertisers, students will want consumers to know why their product is important.
- Explain that student ads should look authentic and professional and should not simply copy an advertisement from an existing product.
- During class, have each student research his/her product and review references. Also, have students decide what type of magazines or newspapers they will design for: a family magazine, a gardening magazine, a farming magazine, etc. This will help them determine how their ad should look. Discuss how the audience will affect what they design.
- Have students begin work in class. The creation of this ad will probably be assigned as homework and will be brought back completed in 3 or 4 days. Some students may need time to look at possible ideas in stores so they should be given several days to complete the assignment.
- When completed projects are brought into class to be shared, have four or five students come to the front together. Each student will show his/her poster. Have classmates identify, or try to identify, what the student was advertising. Have the student explain in a few sentences what was being advertised and what they learned about the topic. They should include why someone would want to buy that product.
Concept Elaboration and Evaluation
After conducting these activities, review and summarize the following key concepts:
- Fertilizer is a supplement that is added to soil to promote healthy plant growth.
- N, P, and K refer to the nitrogen, phosphorus and potassium found in fertilizer.
- Commercial fertilizers are carefully formulated and created to meet the specific needs of plants.
- Have students share their final product in a small group instead of in front of the class.
- Give students the option to use other types of technology to create their ads. Examples include radio broadcast, iMovie, and more.
- Have students use reference books instead of online sources of information. Possible reference books:
- The New Western Garden Book by Sunset Magazine
- California Master Gardener Handbook by Pittinger
- Western Fertilizer Handbook by Western Plant Health Association
Have students include a written report, explaining what they learned about soil supplements while researching their topic.
This lesson was updated in 2013 with funding from California Foundation for Agriculture in the Classroom and a grant from the California Department of Food and Agriculture’s Fertilizer Research and Education Program. The Fertilizer Research and Education Program (FREP) funds and facilitates research to advance the environmentally safe and agronomically sound use and handling of fertilizer materials. FREP serves growers, agricultural supply and service professionals, extension personnel, public agencies, consultants, and other interested parties. FREP is a part of the California Department of Food and Agriculture (CDFA), Division of Inspections Services.
Editor: Shaney Emerson
Executive Director: Judy Culbertson
Illustrator: Toni Smith
Layout and Design: Nina Danner
Copy Editor: Leah Rosasco
Suggested Companion Resources
- Troubled Waters
- Under Your Feet: Exploring Soil Science
- Topsoil Tour
- Home Composting - Turning Your Spoils to Soil
- Phosphate Mining Video
- Potash Mining Video
- Soil Science Videos
- Dig In: Hands-On Soil Investigations
- How a New Evolutionary Map Could Help Farmers Eliminate Fertilizer
- Soil Health Education Resources
- Soil Science Society of America
California Foundation for Agriculture in the Classroom