Oregon Agriculture in the Classroom Logo
Lesson Overview
  • 90 Minutes
  • 1, 2, 4, 5
  • 6th - 12th Grade
  • State Standards:
    NGSS: MS-LS1-5, MS-LS2-5, MS-LS1-4, HS-LS2-4 CCSS: WHST.6-8.1, WHST.6-8.2, SL.8.1,

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Download PDF (Spanish)

Materials List

Soil Testing Kit*
•Jar with lid per group
•One nitrogen, phosphorus and potassium comparator with capsules.*
•One pipette*
•paper cups
•Activity Page: Hungry Plants per student
•Plant Nutrients Background Reading Page per student
•Hungry Plants Exit Ticket per student
•Paper Towel
•3 Poster Size Papers
•3 sticky notes per student
•One Set of Plantionary Cards (6 cards)

Hungry Plants

Categories: Kits , Introduction to Agriculture , Spanish , Agriculture , Plants , Science , Soils

Students will discover that plants, like humans, need an adequate amount of nutrients to grow and stay healthy. Plants require 16 chemical elements for growth and development. Some nutrients come from the air while others are taken from the soil. It’s important to test soil regularly to determine if there are enough nutrients to support plant growth. The soil test kit will help students identify whether the soil sample is fertile or deficient in nutrients. Keep in mind that all plants need nutrients, but requirements vary depending on the type of crop, shrub, tree, etc.

Check out our Testing Soil Nutrients N-P-K Lesson for math applications associated with this topic!

Most soils have an abundance of nutrients, but sometimes nutrients can be diminished or become depleted when they are not replaced after being used up by a plant. Nitrogen, phosphorus and potassium (N-P-K) play a vital role in plant growth. Nitrogen is important for growth, phosphorus stores and transfers energy to be used for reproduction and developing root systems and potassium is responsible for disease resistance. Nutrients can be replaced by adding manure, fertilizer, organic matter or compost to the soil.
Part I: Preparing Soil Samples
1)Divide students into five groups. Have each group use a spoon or small shovel to gather soil samples in the paper cup. Ensure they avoid touching the soil with their hands, as this may alter test results.
Teacher Note: Encourage each group to get a sample from different areas in the garden or around trees and shrubs in order to have the best overall representation of soil nutrients.
2) Dump the soil out on a paper towel to allow soil to dry naturally if needed. Use this time to break up clumps and remove small stones before testing.
3) Place 1/4 cup of soil into a clean jar and add 1 1/4 cups of distilled water.
4) Place the lid on the jar and shake or stir the soil and water continuously for one minute.
5) Using a piece of masking tape, label the jar with the names of students in the group.
6) Set the mixture aside and allow it to stand until it settles. This usually takes 30 minutes to 24 hours depending on the type of soil.
7) Have students refer to the worksheet and hypothesize if each test will result in soil being depleted, deficient, adequate, sufficient or in surplus amounts for each nutrient.

Part II: “Plantionary”

1) Divide students into five groups. Explain to students that they will be playing a quick game of plant Pictionary or “Plantionary”. Each group will identify a person in their group to be the artist, the rest of the group will be guessing. Each group will receive a different word related to plant needs. Explain that you will be timing them and they have 65 seconds to guess their word. The first group to guess correctly should raise their hands when they are done.
2) Once groups are set up and the artist has been identified, distribute one plant plantionary card to each group. Have the artist of the group keep the card face down until you say “go”. Once you say “go” the artist will flip the card, read it and return it to its face down position on the table before starting to draw.
3) After the time has ran out, have each group report to the class what their word was, take this time to make connections to why that word is important for plants.

Part III: Gallery Walk Posters

1) Hang three poster-sized papers around the room, write one of the following questions on each poster.
What do plants need for growth and development?
What are the sources of plant’s needs?
What is fertilizer?
2) Provide each student with 3 sticky notes, instruct students to visit each poster, write an answer for the question on one of their sticky notes and place it on the poster beneath the question.
3) After students have distributed their sticky notes, review each question and the students’ answers with the class. Explain that today, they will be learning about each of the concepts listed on the posters.
Part VI: Plant Nutrients & Soil Testing
1) Distribute the Plant Nutrient Background Reading Page to students.
2) As a class, read through the plant nutrient information. Explain to students that farmers and gardeners often have to supplement nutrients to plants through nutrient-rich plant foods as fertilizers to increase the primary macronutrient levels in the soil. Today, they will be testing soil for those very important primary macronutrients.
3) Provide each group with their testing kits and have them carefully collect their soil sample. Making as little movement as possible, have students take their sample back to their group and avoid disturbing the settled soil.
4) Have students select the appropriate comparator and matching capsule for each test. For example, students will use the purple capsule to test the amount of nitrogen in the soil. The nitrogen comparator has a purple cap and chart.
Purple = Nitrogen
Blue = Phosphorus
Orange = Potassium
5) Use the pipette to fill both the test and reference chambers with liquid from the soil and water mixture. Do not include sediment. Make sure to fill the comparator to the marked line.
6) Work with a partner, one holding the comparator with the liquid and the other partner should carefully separate the two halves of the appropriate capsule and pour the powder into the test chamber. (Hint: lightly squeeze one side of the capsule and twist the other side to gently pull apart the capsule.)
7) Put the cap back on the comparator, making sure it’s sealed. Shake thoroughly.
8) Wait 10 minutes for the color to develop. If the blue color has settled to the bottom of the phosphorus test chamber during the 10 minute period, shake the tube to remix the color into the solution.
9) Compare the color of the solution in the test chamber against the chart and solution in the reference chamber. Repeat steps 2-7 for the nitrogen, phosphorus and potassium test.
10) Have students record their results in the chart provided on the Hungry Plants worksheet and complete the review questions at the bottom of the worksheet.
11) Discuss the review questions at the bottom of the worksheet as a class.
Part V: Exit Ticket
1) Distribute the exit tickets to students at the end of the class discussion to help review key concepts of the day and assess student learning from the lesson.
2) Have students complete the exit ticket after all materials and reference materials from the class have been put away.