Students use the art of soil painting to explore science and the natural world while learning about the color wheel, the importance of soil to agriculture, and why soils have different colors. Grades 3-5

organic matter: a soil component derived from the decay of once-living organisms like plants and animals

parent material: the soil horizon just above bedrock that contains broken up pieces of rock and will eventually break down into soil

primary colors: the main group of colors (typically red, yellow, and blue) on the color wheel which can be mixed together to obtain all the other colors

secondary colors: colors (such as green, orange, or violet) produced by mixing two primary colors

tertiary colors: produced by mixing two secondary colors

topsoil: the upper layer of soil that is rich in organic matter and best suited to growing healthy crops

This lesson integrates the art concept of color with science and soils in a garden setting. In the visual arts, color theory is a body of practical guidance for mixing colors and understanding the visual impacts of specific color combinations. Early color theory principles appeared in the writings of Leonardo da Vinci and others in the 1400s. In the late 1600s, Isaac Newton discovered the color spectrum by experimenting with shining light through a prism. From these beginnings, color theory developed as a tool for artists and designers, and today it is commonly applied through use of the color wheel.

Most color wheels are based on three primary, three secondary, and six tertiary colors for a total of 12 main divisions. A typical artist’s paint or pigment color wheel includes blue, red, and yellow as primary colors. The corresponding secondary colors, formed by mixing two primary colors, are green, orange, and violet. The tertiary colors, formed by mixing a primary color with a secondary color, are red-orange, red-violet, yellow-orange, yellow-green, blue-violet, and blue-green.

A multitude of colors can be found in the garden in everything from leaves and flowers to insects and seeds to soil and rocks. The first part of this lesson will focus on noticing colors in the garden. Students will use the color wheel to determine if the colors of items they have collected from the garden are warm or cool. Then they will classify the colors as primary, secondary, or tertiary.

The second part of the lesson focuses on the agricultural importance of soil and what we can learn about gardens and farms by observing the color of soil. Students will build an understanding of soils and their importance by painting with soil-based pigments. Soils are the foundation of agriculture, providing the support, water, and nutrients that plants need to grow. Garden plants and plants grown on farms depend on healthy soil to grow.

Soils are also important for the beauty their many colors add to our landscape. Most of us overlook this natural beauty because we see it every day. Often these colors blend with vegetation, sky, water, and other natural features. Over the centuries, humans have used soil colors to serve as pigments in bricks, pottery, and art work. These artifacts from the past give us an idea of how early people lived and worked.

Utah has over 1,300 different soil types. Each soil has its own unique characteristics. The attached soil map does not depict the colors of Utah soils, but rather uses different colors to represent different orders of soils. Within each order there are many different types and colors of soils. The map provides a glimpse of the diversity of soils found in Utah.

A lot can be learned about soil by observing its color. In general, lighter colored topsoils are found in dry areas and darker topsoils are found in grassland regions that get lots of rain. The soil found in forested, mountainous areas are generally midway between light and dark. The darkest topsoils are the richest in organic matter, which builds up over thousands of years. Grasslands have lots of organic matter because the soil is densely filled with grass roots. Grasses are constantly shedding old roots and growing new ones. When roots are shed (die), they contribute to the accumulation of organic matter in the soil. Organic matter builds topsoil that is dark and crumbly, contains the nutrients plants need, and holds just the right amount of water for plants to thrive. Soils rich in organic matter tend to be good soils for farming and growing crops.

Even if an area tends to have light colored soil, pockets of darker soil may still be found in places where additional moisture accumulates, leading to more plant growth. Similarly, light soil can be found in areas that are generally darker. In this case, a light soil often shows where soil development is thinner due to slope or as a result of erosion. Also, lighter soil colors can be found in the subsoil. The colors of subsoil and, to a lesser degree, topsoil are based on parent material.

Soils can be grouped into colors like red, pale red, black, brown, yellow, yellowish-red, and grayish-brown. However, describing soils in these terms is not very exact! So, just like the books of colors found in paint stores, there is a book of soil colors used worldwide called the Munsell Soil Color Charts. The color information in this book is based on the soil classification system used by soil scientists for describing soils. Soil samples are compared to the colors in the charts and given a specific value. Agronomists, biologists, archeologists, geologists, zoologists, and other scientists use these charts to document soil colors.

The color of a soil can indicate what kinds of minerals are in the soil and what kinds of plants will grow well in that soil. Iron provides a great variety of pigments. Soils ranging from yellow to brown to red contain iron. Organic matter turns soil a dark color and provides fertile ground for growing crops. Soils with high amounts of lime are almost white. Lime makes the soil more alkaline, or less acidic. Some plants, like blueberries, need acidic soils and would not grow well in a white, alkaline soil. Soils with a green tinge may have high amounts of copper, which plants only need in very small amounts. High copper levels will kill most plants.

General rules about soil color:

• Black, Black/Brown: Dark soils have high organic matter content and are rich in nutrients for plants. These are often deep soils formed in parent materials transported by water, ice, or gravity. This includes glacial deposits and soil deposited by rivers.
• Gold/Yellow: Yellow soils form from certain sandstones.
• Taupe: These are clayey soils with low organic matter content that are formed mainly in residual materials from ancient sea beds.
• Red: High iron content makes soils red.
• Cream: These light soils have high amounts of lime and may form in wind-blown, silty material.

1. Read the book Diary of a Worm by Doreen Cronin.
2. Ask students if they think all soil a worm might travel through is the same color. Hypothesize with the students why soils are different colors. (The minerals in the parent material/bedrock contribute the color; organic matter in the topsoil makes the soil look darker.)
3. Use the Soil Profile Images shown below to illustrate different colors in the soil. 
   

Activity 1: Garden Color Classification

1. Provide each student with a paper or resealable plastic bag. Ask them to go into the garden (or a park or schoolyard) and collect, observe, or take photographs of at least 5-10 items that are different colors. 
2. Display the Color Wheel for the students to reference, and ask them to match the items they collected to the closest color on the wheel. 
3. Point out that half of the color wheel, ranging from red to yellow, is labeled warm. These are colors we associate with warm things like fire or the sun. The other half of the wheel, ranging from green to purple, is cool. These are colors we associate with cool things like water or a shady forest. Ask the students to group the items they collected into cool colors and warm colors. 
4. Use the information in the Background Agricultural Connections to discuss the difference between primary, secondary, and tertiary colors and how artists and designers use particular colors to evoke different feelings and show contrast or depth. Ask the students to classify the color of each item they collected as primary, secondary, or tertiary. 
5. Remind the students about the soil color discussion you had after reading Diary of a Worm. Share the information about soil color from the Background Agricultural Connections with the students. Discuss the importance of organic matter in soil and how it colors the soil. Where does organic matter come from? Organic matter is not alive, but it comes from living things.
6. Discuss the differences between living and nonliving things.
7. Have students sort and categorize the items they collected into living and nonliving things. Ask the students if they can describe some relationships that exist between the items they have collected (e.g., rocks become soil by freezing and thawing; plants become part of soil when they die and decompose; soil anchors and provides water and nutrients to plants; insects may eat plants or help plants by eating other harmful insects, etc.)

Activity 2: Soil Painting 

1. Use the information in the Background Agricultural Connections to discuss the value of soil and what we can learn by observing soil color. 
2. Share a soil map of your state. Refer to your local soil resources or use the Soil Orders Map of the United States. Discuss various locations where students have seen different colors of soils.
   • Note: If you teach in Utah, use the Utah Soils Map.
3. Tell the students that they are now going to make a journal cover by painting with different colors of soil. 
4. Prepare a mixture of watered-down glue (about two parts water to one part glue). The mixture can be sealed in a jar to use again. Place some of the diluted glue in containers for adding soil to make the soil paints, and some in separate containers to keep plain for applying the toilet paper strips. Note: You may wish to do this step prior to class to save time. 
5. Provide each student with a single piece of 8.5" x 11" construction paper (light gray or white works best), three strips of toilet paper, a paint brush, and access to a container of the diluted glue. 
6. Ask students to initial or write their names on the back of the paper.
7. Instruct them to tear the three, three-square lengths of toilet paper into horizontal thirds (this is easiest to do if the three squares are folded and then torn). 
8. The students should place the horizontal pieces across the construction paper so that it is covered. Then they will use their brushes and the plain diluted glue to wet/texture the toilet paper to the page, one strip at a time. Allow the pages to dry overnight.
9. After the pages are dry, provide the students with access to each different color of soil, and allow them to experiment with the amount needed to achieve color (not grit!). A good starting point is ½ tablespoon ground soil to 4 tablespoons watered-down glue, but the students may choose to use more or less soil to create darker or lighter paint. 
10. Give the students time to paint their journal covers. This can be done in a variety of patterns.
11. If possible, avoid moving the pages while they are still wet by leaving them to dry where they were painted. Allow pages to dry overnight. 
12. The following day, instruct the students to fold the pages in half, and place a hole-punch at the top and bottom of the fold. 
13. Have the students write or draw on pages to put in the journal, or fill it with visuals related to soils, life science, or color in the garden. For example, you may have the students place inside the journal a hole-punched soils map, a soil profile, and a page where they’ve written what they learned about soils. 
14. String a piece of twine through the holes to attach any pages that are placed inside.

After conducting these activities, review and summarize the following key concepts:

• Soil is the foundation of agriculture.
• Soil anchors plants and provides them with the water and nutrients they need to grow.
• Living plants die and decompose to become nonliving organic matter, which makes soil dark and fertile. 
• Different colors of soils are created by different parent materials (mineral content) and different levels of organic matter.
• The color wheel is a tool used to understand how colors relate to each other. 

1. http://www.fao.org/soils-2015/resources/fact-sheets/en/#c326621

• A Handful of Dirt
• Diary of a Worm
• Dirt: Secrets in the Soil (DVD)
• Dirt: The Scoop on Soil
• Harvesting Friends, Cosechando Amigos
• Jump Into Science: Dirt
• My School Yard Garden
• SOIL Reader
• Sand and Soil: Earth's Building Blocks
• Seed, Soil, Sun: Earth's Recipe for Food
• Soil Painting
• Soil Samples (Soil Texture)
• Soil! Get the Inside Scoop
• Soil, Not Dirt
• The Curious Garden
• The Dirt Book: Poems About Animals That Live Beneath Our Feet
• The Extraordinary Gardener
• The Soil in Jackie's Garden
• Under Your Feet: Soil, Sand and Everything Underground
• You Wouldn't Want to Live Without Dirt!