Plant Growth in Different Soil Types

Plant Growth in Different Soil Types

Target Grade Level / Age Range:

2nd Grade

Time:

Approx. 1 hour plus several days of observation

Purpose:

Students will show that plants grow more successfully in fertile soil when compared to other materials.

Materials:

  • Soybean seeds
  • Paper cups with holes in the bottom for drainage
  • Four soil types:
    • Sand
    • Silt
    • Clay
    • Loam
  • Markers

Suggested Companion Resources (books and websites)

Vocabulary (with definitions)

  • Soil – a complex mixture of rock fragments, organic material, air and water
  • Nutrients – substance essential for growth. Nitrogen, phosphorus, and potassium are key nutrients.
  • Fertile – capable of producing abundant crops or vegetation
  • Sand – the largest soil particle size
  • Silt – the medium-sized soil particle size
  • Clay – the smallest soil particle size
  • Loam – a mixture of multiple soil particle sizes

Background – Agricultural Connections (what would a teacher need to know to be able to teach this content)

Plants need a few key things to grow. Those things are nutrients, water, and sunlight. Usually their nutrients come from the soil they are growing in.

  • There are three different textures of soil. A mixture of multiple textures is called “loam.”
    • Sand is the largest particle size. Since it is large, it has excellent drainage properties. However, not all plants grow well in such well-drained soils. Sand also has different nutrient holding capacities, as it has less surface area than smaller particle sizes. Because of this, it is possible to run into nutrient deficiencies on these types of soils more often.
    • Silt is a medium particle size. It drains fairly well, and holds nutrients fairly well. You could think of it like the baby bear in the story of Goldilocks.
    • Clay is the smallest particle size. Because of its small size, it retains water much more than the other particle sizes. However, since there is much more surface area of particles within the soil, there is a higher nutrient holding capacity.
    • Realistically, farmers rarely have a field of pure silt or pure clay. Most of the time there will some kind of mix of soil types. Agronomists and soil scientists will test these soils first by making a “ribbon” from the soil. Depending on the length of the ribbon and how gritty the sample feels, they can estimate percentages of each soil texture, and identify it using the soil texture triangle.
  • Soil texture is not the only variable in determining soil quality, but it is one of the main things to take note of about a soil.
    • Note: if you are unsure where to look for these different soil types, a local NRCS or Extension office may be able to assist in finding them locally.
  • Plants need both macronutrients and micronutrients to grow.
    • The three main macronutrients needed for plant growth are nitrogen, potassium, and phosphorus. These three are commonly referred to as NPK.
    • Some micronutrients needed for healthy plants include molybdenum, copper, chlorine, iron, manganese, and so on.
    • A full list of essential elements can be found here: http://soils.wisc.edu/facstaff/barak/soilscience326/macronut.htm
    • In terms of soil chemistry, these elements generally are represented as cations, or positively charged ions. These cations are held onto soil particles based on the soil particle’s surface area and cation exchange capacity (or CEC). Different soil types have different CECs, and clay particles have a higher CEC. Organic matter, however, has a very high CEC, and can be used to help supplement sandier soils.
  • Plants need water to grow, but do not do well when flooded. This could be an opportunity to talk with students about how different plants adapt to different environments. For example, cactuses and cattails need very different environments to grow.
  • Plants also need sunlight to grow and photosynthesize. As an extra experiment, your classroom could put a couple plants in a closet or underneath a desk or sink to see how well they grow past germination.

This lesson will use soil texture as a variable in a simple experiment. This will also be an exercise in coaching students in descriptive and observational language.

  • If the seeds in this lesson do not grow much differently in the different soil textures, talk with the class about what that might mean about the soybeans. Perhaps this is a crop that farmers in many places can use. Talk about how the lack of a result is also a result.
  • A couple days into the experiment (as long as the seeds are moist and warm), the seeds should start to germinate. For a seed to simply germinate, it only needs heat and moisture. For a plant to grow past this stage, it will need more nutrients.

Interest Approach or Motivator

Give each student a small sample of sand, silt, and clay on a paper plate.  Have them describe each one. Let them feel each sample. Record information in a chart together as a class.  Encourage them to use as many descriptive words as they can.

Procedures

  1. Start the lesson by asking students what they know about soil.
    1. What is soil?
    2. What does it look like?
    3. What does it feel like?
    4. Can soil look and feel different?
    5. Describe soil in the desert.
    6. Describe soil in a swamp.
    7. What is soil like in a forest or a farm field?
  2. Lead into the idea of soil texture. Introduce the idea of soil particles. Use the vocab words sand, silt, and clay. Talk about how a mixture of these particle types is called a loam.
  3. Have students discuss what they know about sand, silt and clay. Where would you find these things? How do they feel or look different?
  4. Talk with students about what plants need to grow. They should say things like nutrients, water, air, sunlight, and soil.
    1. Ask students if the type of soil matters to the plant’s development. Why do they think that?
    2. Have students bring out their science journals. At the top of one page, have them write, “Does the type of soil matter to a plant’s development?” Beneath, have them write their initial hypothesis.
  5. Next, split the class into smaller groups. Groups of 4-5 would be best.
    1. Tell the students to pick a group name. (You could also assign them names, like A, B, and C.)
    2. Give each group 4 small cups and 12 soybean seeds.
  6. Tell the students that they will be testing their hypotheses by planting soybean seeds in four soil types; sand, silt, clay, and loam.
  7. Help the students put a different soil type in each cup. There should be about the same amount of soil in each.
  8. Help the students plant 3 seeds in each cup.
  9. Tell the students to label their cups with the soil type in them and their group name. Depending on the type of cup used, students may need markers for this step.
  10. Give each cup the same amount of water and sunlight. Ask students why this might be important. Help them realize that will help them know any differences between them are only because of soil type.
  11. Wrap up this lesson by telling students that they will be monitoring and journaling about the plants for the next couple of weeks.

Follow up lessons:

  1. Allow students some time to journal about what they can see the plants doing every couple of days. Tell students to include drawings of what they see, if they so desire.
  2. Students will record the growth of the plants in a notebook. Over time, students will hopefully see that plants in silt or loam are growing the best.
  3. Talk about how the different particle sizes can make a difference in root development and water movement. Have students write and draw in their journals their final thoughts about soil textures and plant growth.

Essential Files (maps, charts, pictures, or documents)

Did you know? (Ag facts)

  • Iowa’s soil was formed primarily by glaciers.
  • Iowa has one of the only Loess deposits in the world!

Extension Activities (how students can carry this beyond the classroom)

  • Follow up this lesson with lessons about plant growth and development. Soybean growth (dicotyledonous plant) can be compared to corn growth (monocotyledonous plant).
  • Do an art activity where students paint pictures with different colors and textures of soils. Soil can be put in a blender and mixed with water to create a kind of paint.
  • Do a writing activity where students have to describe different soils using adjectives.
  • Create a math percentages lesson where students use the soil textural triangle to find the percentage of the third soil texture.

Sources/Credits

Author(s)

Michelle Nelson

Chrissy Dittmer

Organization Affiliation

Sioux City Community Schools

Iowa Agriculture Literacy Foundation

National Agriculture Literacy Outcomes

 

  • T1.K-2.a: Describe how farmers/ranchers use land to grow crops and support livestock
  • T1.K-2.b: Describe the importance of soil and water in raising crops and livestock

Iowa Core Standards

  • Science:
    • 2-PS1-1: Plan and conduct an investigation to describe and classify different kinds of materials by their observable properties.
    • 2-PS1-2: Analyze data obtained from testing different materials to determine which materials have the properties that are best suited for an intended purpose.
    • 2-LS2-1: Plan and conduct an investigation to determine if plants need sunlight and water to grow.
    • 2-LS4-1: Make observations of plants and animals to compare the diversity of life in different habitats.
  • Language Arts:
    • L.2.1: Demonstrate command of the conventions of standard English grammar and usage when writing or speaking.
      • E. Use adjectives and adverbs, and choose between them depending on what is to be modified.
    • L.2.5: Demonstrate understanding of word relationships and nuances in word meanings.