Middle and High School
The pedosphere, aka soil, is an essential component of our ecosystem and plays a pivotal role in sustaining life. Students in your class will dig learning about the different soil types, their significance, and the factors that influence them.
In a previous post, Soil chemistry facts you'll dig, we shared a mound of information about elemental composition, minerals, ion exchange, and soil solution. This post lays the groundwork to further explore soil types, their importance, and factors that affect soil composition.
We also share hands-on activities you can use to deepen students' scientific understanding and encourage their active engagement in environmental stewardship.
Before digging into the activities, give your students the dirt on dirt:
What Are Soil Types?
Soil is the loose material that covers the Earth's surface (the pedosphere), consisting of minerals, organic matter, water, and air. Soil types can be classified based on composition, texture, and color. The three primary soil types are sand, silt, and clay, with varying proportions determining the soil's overall characteristics, as shown in the Soil Types Guide below.
The Importance of Soil:
Soil is a valuable natural resource that serves several critical functions:
Nutrient Cycling: Soil is a reservoir for essential nutrients, such as nitrogen, phosphorus, and potassium, vital for plant growth and development. Various soil processes make these nutrients available to plants, ensuring their growth. Of course, plants must have water to facilitate the transfer of these essential nutrients. Water serves as the solvent and carrier of food nutrients from the soil to plants. It may seem like a chore, but that’s why it’s so important to wet our plants!
Water Storage and Filtration: Soil can hold and release water, crucial in regulating the water cycle. It acts as a natural sponge, preventing excessive runoff and reducing the risk of flooding. Additionally, soil acts as a filter, purifying water as it percolates through the layers, ensuring a clean water supply.
Habitat for Organisms: There’s a fungus among us, and that’s ok! Soil is a rich ecosystem that harbors many organisms, including fungi, bacteria, insects, worms, and plant roots. These organisms contribute to soil fertility, decomposition of organic matter, and the overall health of the ecosystem.
Carbon Sequestration: Soil is vital in mitigating climate change by acting as a carbon sink. Organic matter in the soil captures and stores carbon dioxide, reducing its atmospheric concentration.
5 Factors Affecting Soil Composition:
Pedogenesis is the study of the origin and formation of soil. Various factors influence the composition and properties of soil. Here are the five broad categories:
- Climate: Climate affects the rate of weathering, organic matter decomposition, and overall soil formation. Temperature, precipitation, and wind patterns influence the processes that shape soil composition.
- Parent Material: The parent material refers to the underlying geological material that produces soil as it’s exposed to the atmosphere. Different types of rocks and minerals can yield soils with varying characteristics.
- Topography: The physical features of the landscape, such as slope, elevation, and aspect, influence soil formation. Slopes can affect water drainage and erosion, leading to variations in soil types.
- Organisms: Living organisms, including plants, animals, and microorganisms, have a significant impact on soil composition. Their activities, such as root growth, nutrient cycling, and organic matter decomposition, contribute to the formation and fertility of soil.
5. Time: Tick-tock soil formation is a slow and continuous process over long periods. The age of the soil affects its development, fertility, and degree of weathering. Sand dunes are an example of young soil, and early forest soils are an example of the oldest soil.1
This illustration highlights how these five factors and processes are involved in soil formation.
Soil size matters!
Grain size refers to the diameter of individual particles or grains in a material such as soil, sediment, or rock. The size can range from very small particles, such as clay, to larger particles, such as sand, and even larger particles, like gravel and boulders.
Scientists determine grain size through various methods, including visual estimation, sieving, laser diffraction, and microscopic analysis. Grain size tells us a lot about the geological history, processes, and physical properties of the Earth's materials. Geology Is the Way presents key methods for classifying and measuring clastic rocks and sediments based on the Udden-Wentworth scale, arenitic grain sizes chart, and Sieve analysis.
Now that we’ve unearthed some fundamental facts, you can mine through the hands-on soil activities we’ve shared below. Hint: you’ll need this Soil Types Guide if you really want students to get their hands dirty!
We have created this comprehensive Soil Types Guide to visually represent the diverse range of soils around the world. This guide is a valuable resource for science teachers and students, offering a clear and concise overview of the main soil types and their key features.
As students participate in activities, they can easily see soil composition and classification in an organized and accessible format. It categorizes soil types based on texture and composition, providing a quick reference for understanding their unique properties.
- Soil Identification Activity: Use the Soil Types Guide for a hands-on activity where students observe and identify different soil types. Students can collect soil samples from various locations and use the guide to classify them based on their physical properties, such as color, texture, and particle size. You may find this handy Soil Formation Collection.
- Soil Composition Investigation: Incorporate the Soil Types Guide into an investigation where students analyze the composition of different soil types. Students can compare the organic matter content, mineral composition, and nutrient levels of different soils, using the guide as a reference for identifying and understanding the variations. You may find this handy, Soil, Sands, and Gravel Set.
- Soil Erosion Demonstration: By referencing the Soil Types Guide, design a demonstration to showcase the impact of different soil types on erosion. Students can set up miniature landscapes with various soil types and simulate rainfall or water flow to observe how soils erode differently based on their characteristics, such as particle size and structure. You may find this handy Modeling Stream Erosion and Deposition Kit.
- Soil pH Experiment: Use the guide to explore the pH levels of different soil types. Students can collect soil samples and test their acidity or alkalinity using pH testing kits. By referring to the guide, they can understand how soil pH affects plant growth and its significance for agriculture and gardening. You may find this handy LaMotte® Acidity Test Kit.
- Soil Nutrient Availability Investigation: Use the Soil Types Guide to investigate nutrient availability in different soils. Students can collect soil samples, perform nutrient tests, and compare the nutrient profiles of various soil types. This activity can help students understand the importance of soil fertility and how it impacts plant growth and ecosystem dynamics. You may find this handy, LaMotte® NPK Soil Test Kit.
- Soil Conservation Lesson: You can use the guide to educate students about soil conservation strategies. Your lesson plan may explain how different soil types have varying vulnerabilities to erosion and degradation. By referencing the guide, encourage students to identify a conservation method for each soil type, such as contour plowing, terracing, or cover cropping. You may find this handy, Global Threats to the Environment Chart.
- Soil Permeability Experiment: Use the Soil Types Guide in activities demonstrating soil permeability. Students can collect soil samples with different textures and conduct tests to measure the rate at which water infiltrates each soil type. By analyzing the results with the help of the guide, students can understand the relationship between soil structure and permeability. You may find this handy, Soil, Sands, and Gravel Set.
- Soil Microorganisms Study: The guide can be used to introduce students to the diverse microorganisms present in different soil types. Students can collect and examine soil samples under microscopes, identifying and classifying the microorganisms they find. By referring to the guide, they can learn about the role of soil microorganisms in nutrient cycling, decomposition, and soil health. You may find these handy, Boreal2 Microscopes, HM Advanced Series and LaMotte® BioPaddles.
- Soil and Plant Adaptations Research: Students will be excited to explore the relationship between soil types and plant adaptations. Students can choose specific soil types from the guide and research the plants that thrive in those soils. They can present their findings, highlighting the specific adaptations plants have developed to survive and grow in different soil conditions. You may find this handy, APES Lab #1: The Soil Factor: How Does Your Garden Grow?
- Soil Pollution Investigation: Using the Soil Types Guide, students can investigate soil pollution. Students can collect soil samples from different areas, including urban, agricultural, and industrial locations. They can test the soil for pollutants such as heavy metals or pesticides and refer to the guide to understand the potential impact on soil quality and ecosystem health. This activity can also raise their awareness about environmental issues and the importance of soil conservation. You may find this handy, LaMotte® Electronic Soil Outfit.
Understanding soil types, their importance, and the factors influencing soil composition is crucial for students to grasp the significance of soil in our ecosystem. Exploring these topics can inspire curiosity, foster environmental awareness, and instill a sense of responsibility toward preserving this natural resource.
1. University of Idaho: Alfisols