Soil Ecology Archives - Eva Varga

May 16, 2015

Mud, or sediment, is an active part of aquatic ecosystems. Sediment varies widely within and among ecosystems in its biotic and abiotic characteristics.

Biotic factors are the living components of a community or larger ecosystem.

Abiotic factors are essentially non-living components that effect the living organisms of a community.

In many ecosystems sediment can release excess phosphorus (a common aquatic pollutant) into the water column causing internal eutrophication.

When studying aquatic ecosystems, people often think about the water and things that live in the water. However, the mud at the bottom of lakes and wetlands – the sediment – is an active part of these ecosystems. A wide diversity of organisms, both macroscopic and microscopic, live in sediments.

Sediments can often be a source of nutrients, especially nitrogen and phosphorus. Nutrients released from sediments are part of an ecosystem’s internal load (as opposed to the external load, which consists of nutrients that come from outside the  ecosystems).

Most commonly, sediments release large amounts of phosphorus as phosphate, sometimes causing excessive algal growth, harmful algal blooms (growth by algae that produce toxins), and even fish kills (as dead algae fall to the bottom of an ecosystem, fuel bacterial decomposition, and consume oxygen). These negative effects caused by sediment release of phosphorus are called internal eutrophication.

STEM Club: Life in the Mud @EvaVarga.netLife in the Mud

Gather around a picnic table at a local pond or wetland area. Lead the class in a discussion about how the abiotic and biotic components of the pond could interact. Use what the students have said to link the nutrient content of the sediment and water to the activity of living things in the water. For example, nutrients released from the sediment can enhance growth of algae in the water.

Ask students to hypothesize about what they expect to see in the mud. What makes up the sediment? What makes up the pond water? Describe some possible interactions between the sediment and the water column.


  • 2 quart jars with lids for each group
  • Mud from a pond (enough for about 1/3 of each of the jars)
  • Water from a pond–algae WILL be there (enough to fill the other 2/3 of each of the jars)
  • Shovel (one for each group)
  • Water quality kits for measuring nutrients for each group
  • Compound microscope (for each pair of students)
  • Microscope slides
  • Optional Materials: Dissolved oxygen meter, dissecting microscope, thermometer, conductivity meter, funnel

STEM Club: Life in the Mud @EvaVarga.netExperimental Set Up

  1. Split into small groups and distribute materials evenly. Each group should disperse to a different area around the pond perimeter to begin the experimental set up.
  2. Each group should utilize the water quality kit to test the pond water and record the data in their journals.
  3. Each group sets up the jars: one with nothing but pond water in it (control group) and another jar with 1/3 pond sediment and 2/3 water in it (treatment).
  4. After collecting mud samples, return to the table. Lead students through the process of developing a hypothesis with the guiding questions: What differences do you expect to see in the treatment group and control group in about a week? Why do you think those differences might occur? Possible hypothesis: There will be a greater number of algae in jar with sediment and pond water compared to the jar with only pond water.
  5. Check the jars after one week. If you do not see obvious responses, check them again after two weeks as it may take some time for visible algal growth to occur.

Data Collection

  1. Qualitative Observations: appearance of the water and sediment, look for evidence of algae growth—cloudy water and green “slime” on the sediment; any bubbles coming from the sediment, smell, layers in sediment evidenced by color difference or texture changes; macroscopic organisms in either sediment or water; bacterial growth (slime).
  2. Quantitative Observations: use a microscope to count the algal cells in the water in each jar; if available, test the water in each jar with any available nutrient water testing kit (nitrogen and/or phosphorus), depth of water and sediment over time, water temperature, conductivity and dissolved oxygen, pH.

If you would like to do undertake this outdoor lab activity with you students, I’ve created a free printable student page, Life in the Mud, for your use. If you download it, please leave a little note in the comments.

May 8, 2015

Soil is rarely devoid of life. Soil which supports plant life is teeming with many soil organisms, the majority of which are too small to see. Some examples of soil organisms are fungi, bacteria, nematodes, diatoms (algae), earthworms, ants, centipedes, millipedes, beetles, snails, and slugs. All these soil creatures and more make up the soil community. In STEM Club, we sought to discover for ourselves, what lives in our soils?

Most fungi and bacteria are supported by relationships with plant roots, so they stay close to plants. Any creatures that live on fungi and bacteria also stay close to the roots. Other larger herbivores, like beetles, ants, centipedes, and termites, feed closer to the surface where more plant debris is located.Therefore most soil creatures live within a few inches of soil closest to their food sources.

STEM Club: What Lives in Our Soils @EvaVarga.netThis community of organisms is deeply involved in the soil food web. It’s basically a recycling program, where plant and animal residues are broken down by a chain of soil consumers (nematodes, bacteria, fungi, mites, earthworms, etc), who are then consumed by birds and other mammals, cycling carbon and essential nutrients.

Soil protects soil organisms from harsh sun, wind and, rain, while still providing air, water, and nutrients essential to life. When soil organisms break down plant and animal debris they change the structure of the soil. Creatures like earthworms break down larger vegetative clumps into smaller clumps of organic matter, making the soil structure finer. In a good plant debris-based soil, the actions of earthworm, as well as the amount of organic matter, greatly increases the soil’s ability to hold nutrients and water, as well as structure (pores).

Soil lacking in oxygen, water, and organic matter would be very bare and devoid of biodiversity. The area would consist only of a few, very specific kinds of soil organisms and specific plants that could tolerate these challenging environmental conditions.

What Lives in Our Soil?

Can you think of any other examples of food webs? What are some reasons why a soil would not have a layer of organic matter or humus near the surface? What would be some environmental strategies to remedy such a soil? What would happen if a group from the soil food web (fungi, animals, plants, insects, earthworms) suddenly disappeared?

STEM Club: What Lives in Our Soil? @EvaVarga.netThe goal of this activity is to discover what lives in soil. Students will select a location to collect a soil sample, return to the classroom, and thereby note a variety of characteristics of the soil (moisture content, texture, color, etc.).


  • Small shovel(s) or trowel(s)
  • 1-liter plastic freezer bags
  • Plastic jars
  • Magnifying glasses
  • Permanent marker
  • Journals
  • Map of school grounds, town, or county (geographically and by elevation)


1. Preparation :: Take note of locations that the students would be interested in taking samples from. Be sure to have a variety of locations:

  • Garden or flower bed
  • Wooded area
  • Near a parking lot
  • Near a sidewalk
  • Turf (grassy area)

Have a table in the classroom or other open space ready for observing soils. If students will be drying soil, you’ll need a place where soils can be left for several days
Have students draw a map of the school grounds.

2. Digging Soil :: At each selected area, have students:

  • Observe location and vegetation
  • Describe location and vegetation orally
  • Write about location and vegetation in journals
  • Use trowel or shovel to collect several clumps of soil
  • Place soil in freezer bags

3. Observations :: Place soil samples on table or other open space. Divide students into groups and distribute one soil sample bag per group. Observe characteristics of the soil
which may include:

  • Gravel
  • Rocks
  • Sand
  • Earthworms
  • Ants
  • Other soil creatures
  • Color
  • Moisture
  • Texture

4. Record observations by location on chart (sample below). Predict from chart which soils might be best for growing crops.

STEM Club: Soils Are Alive

Extension Activities

  • Develop an inquiry project to further investigate your prediction in step 4.
  • Choose a soil organism and write an expository paragraph (include: name, appearance, role, supporting details, and conclusion).
  • Think of three animals that live in the soil and the homes they build. Students draw a soil community that includes small creatures, creatures above the soil, and plants.
  • Create an informative poster to illustrate the soil food webs (include at least five trophic levels).

You can learn more about the activities we undertook in STEM Club here:

Soil Ecology Activities for Middle School

Cycles and Ecosystems {Free Printable}

Rain Gardens & Composting

Soils Support Agriculture: Ideas to Integrate Writing

Let’s Get Dirty: Soil Horizons & Particle Size

Let’s Get Dirty: Life in the Mud


May 2, 2015

Soil is the part of the ground where plants grow. Soil is a mixture of tiny particles of rock and rotting plant and animal material, with water and air between them. Soils help plants grow in two ways. First, soil holds the plants into place. Second, soil contains nutrients that plants need in order to survive. These nutrients include water, phosphorous, nitrogen, and potassium.

Over the course of the next few weeks, STEM Club will be investigating soil ecology as a part of the Year of Soils. I’ve shared a few of our past endeavors relating to soils here:

Soil Ecology Activities for Middle School

Cycles and Ecosystems {Free Printable}

Soils Support Urban Life: Rain Gardens & Composting

Soils Support Agriculture: Ideas to Integrate Writing

STEM Club: Let's Get Dirty (Soil Ecology)

Today, I share a lesson on soil horizons and particle size.

Soil Horizons

Soil particles vary greatly in size. The largest particles settle to the bottom first. The fine particles settle slowly; some are suspended indefinitely. The amount of open space between the particles has much to do with how easily water moves through the soil. This also determines how much water the soil will hold, which has a major effect on the type of plants that can grow in the soil.

STEM Club: Let's Get Dirty (Soil Ecology)

Things to look for in soil are color, texture, structure, depth, and pH. A general soil profile is made up of a litter layer, A horizon, B horizon and C horizon. A soil sampling device (pictured in the collage above) allows you to gather data on the soil makeup on any site.

Soil Particle Size

Soil scientists classify soil particles into sand, silt, and clay. Scientists use these three components and the calculated percentages on the texture triangle to determine the textural class of the soil at a given site.

A soil’s texture depends on the size of its particles and living things depend on the right texture to thrive in the soil. Every soil type is a mixture of sand (2mm – 0.05mm; feels gritty), silt (0.05 – 0.002mm; feels like flour), clay (Smaller than 0.002; feels sticky when wet), and organic matter. Squeeze some soil between your fingers. Is it crumbly? Sticky?

STEM Club: Let's Get Dirty (Soil Ecology)

Let’s Get Dirty ~ Terrestrial Soils

One of the best activities to engage kids in the study of soil ecology is the sample the soils around your home or school yard. Begin by asking the following questions:

1.  Are there different types of soil near your home?

2.  What texture class is this soil?

3.  What is the particle size make-up of this soil?

The answers generated prior to the investigation are part of your hypothesis. Record your ideas in your science notebook before you begin and give reasons. Why do you suppose the soil in your yard is predominately sand? What experience or prior knowledge do you have to help you make this statement?


  • 1 Soil probe
  • 1 Metric ruler
  • 1 Quart jar with lid
  • 1 Set index cards for diagrams


  1. Use the soil probe to collect soil cores as deep as possible from a predetermined site.
  2. Diagram and measure the depth of each layer or horizon in your sample.
  3. Fill the quart jar at least half and no more than two thirds full.
  4. Fill the rest of the jar with water, seal tightly and shake vigorously for 10 minutes. Let the jar stand for 24 hrs.
  5. The next day, mark the soil layers of each sample on an index card placed behind the bottle. Mark the top of the soil and the points where the layers change. Calculate the percent of sand, silt and clay in your sample. To do this, measure the following marks you made on the card: entire height, sand (bottom) layer, silt (middle) layer, and clay (top) layer. Then take the height of each layer by the total height and multiple by 100. Record the figures on the data sheet.

STEM Club: Let's Get Dirty (Soil Ecology)
Analysis of Results

  1. At which site was the soil the most sandy? silty? mostly clay?
  2. Do you think that this is a trend and would be found at other sites? Explain.
  3. What are some factors that may change the results of this experiment? Explain.


  1. Did you achieve your hypothesis? Explain.
  2. What did you learn by doing this exercise?
  3. Do you think the soil will be the same at other sites (park, forest, meadow, near the shore of a lake or river, etc.)? Design an inquiry project to learn more.

February 10, 2015

In January, the U.S. Department of Agriculture (USDA) began its celebration of the International Year of Soils to highlight the importance of healthy soils for food security, ecosystem functions, and resilient farms and ranches.


This post contains affiliate links. Please see my disclosure statement for more information. 

Healthy soils are the foundation of agriculture. In the face of mounting challenges such as a growing global population, climate change, and extreme weather events, soil health is critical to our future. Healthy soil is essential as global demands rise for food, fuel, and fiber. Soils also play a crucial role in food security, hunger eradication, climate change adaptation, poverty reduction, and sustainable development.

“Soil conservation is important because if we do not produce food , we do not eat.”

Over the course of the year, the Soil Science Society of America (SSSA) and other partners, will impart the importance of soil via monthly themes. Along with resource specialists and educators around the world, I will share with you the lessons and activities that I use with my own children. It is my hope that you find inspiration and resources to integrate these soil science lessons into your homeschool curriculum.

To begin, I have created this post as a means of sharing with you the print and online resources that I will be using with my students. This page will be updated periodically as we progress in our studies.

Print Resources for All Ages

Did you ever consider that with no soil there would be no life? Know Soil, Know Life  will introduce you to an amazing world—the world beneath your feet. Published by the American Society of Agronomy, it provides a solid foundation about the world of soils. It is perfect for anyone desiring to know more about soil ecology. High school or undergraduate students will find Know Soil, Know Life is an easily accessible resource, but this book is for all ages. Everyone interested in being more environmentally conscious—the urban dweller, the young naturalist, the home gardener—can learn about the diversity of soils and their importance in our environment.

“We speak a lot of the importance of sustainable food systems for healthy lives. Well, it starts with soils.” ~ José Graziano da Silva, FAO Director-General

Also published by the American Society of Agronomy, SOIL! Get the Inside Scoop, provides a strong introduction to soil science for elementary students. Excellent descriptions of soil composition, importance of soil in the environment, and types of soil. This 36-page, full-color book explores how soil is part of our life ~ the food we eat, the air we breathe, the water we drink, and even the houses in which we live. The clear photographs and clear graphics enhance the text. The voices of actual scientists discussing the importance of soil scientists speaking directly to students brings the message of soil conservation home.

“The multiple roles of soils often go unnoticed. Soils don’t have a voice, and few people speak out for them. They are our silent ally in food production.” ~ José Graziano da Silva, FAO Director-General

Another fabulous resources is Life in a Bucket of Soil (Dover Children’s Science Books) by Alvin and Virginia Silverstein. The text and illustrations combine to introduce middle school students to the world of soil. I selected this one as our unit study spine and will be using it as guide as we undertake numerous hands-on activities.

Though this is a revised edition of the original 1972 publication, it is an excellent resource for homeschool. I particularly love that the illustrations are simple enough that we can utilize them as guides for our own nature journal entries. I’ve learned over the years that kids sometimes need examples to help them with their own illustrations.

Online Resources & Lesson Plans

In February, the theme is Soils Support Urban Life. Join me as I share lesson plans and activities to explore how rain gardens, living roofs, and composting can improve soil ecology – Do Your Part with Rain Gardens & Composting.

The March theme is Soils Support Agriculture. In my post, I share ideas to integrate writing and a contest sponsored by the California Foundation for Agriculture in the Classroom.

In April, I will share lessons and activities to teach students how Soils Clean and Capture Water. In May, the theme is Soils Support Buildings & Infrastructure.

For further soil ecology resources consider some of my earlier posts:

June 26, 2010

As a part of our current unit study, we discussed the geology and soil composition of Africa.  Most of African soils are volcanic, meaning they are formed from rocks and ash that have been blasted out of volcanoes.  These soils are particularly rich in minerals.  Minerals are freed from rocks through erosion.

Depending upon the steepness of the slope, the kind of soil, and the amount of vegetation, different amounts of water soak into the soil.  After the water soaks into the soil, plant roots make good use of it.  If the soil is porous, some of the water continues downward until it accumulates in aquifers or underground rivers.

In the dry areas of Africa, there is usually too little vegetation to break the fall of rain.  During the wet season downpours, raindrops smash onto the bare soil, loosen particles, and carry them off the land, along depressions, down little gullies and into creeks and rivers.  Soil erosion is a huge problem in Africa and has been for a long time.  The accumulation of silt at river mouths can be a mile thick.

Over time, the chemical composition of soil may change as animals add their feces to the soil.  Soil can also move vast distances by the action of rivers.  The Nile River carries soil along its 4,000 mile length from the Ethiopian mountains and the East African highlands through Egypt to the Mediterranean Sea.  As the river water flows into the sea, soil particles settle and produce a great mudflat – a delta – spreading out from the river’s mouth.  Because the soils of the Nile Delta were so fertile, agriculture flourished as long as 12,000 B.C. and became the basis of the ancient Egyptian civilization.

Our Experiment

Question :: How does soil type affect the amount of runoff ?

Hypothesis ::  Each of the kids described what they expected to happen.  All were in agreement that they expected the sand to runoff the fastest, then clay and finally dirt.  Additionally, they all predicted that the grass roots would hold in the soil and absorb the most water, resulting in the least amount of runoff.

Materials :: 

  • 4 shallow boxes
  • 3 different soil types (we used dirt, sand, and clay)
  • Sod to fill one box
  • Scissors
  • 3 glass jars
  • Watering can
  • Water
  • Stopwatch

Procedure ::

  1. We set up each soil type in a shallow box.  In one corner of each box, we cut a V shaped notch.
  2. We filled the watering can with water.
  3. We set the box on an incline on a step with the glass jar positioned under the notch.
  4. Working with one soil type at a time, we allowed it to rain gently above and recorded the time it took for the glass jar to fill with water.
  5. We then set up a fourth box with grass and soil (essentially I just dug up various grass clumps from the perimeter of our yard and set them in the box – getting a little weeding done while we did our science lesson)

Data ::

  • Dirt –  1.20 minutes
  • Clay –  .19 minute
  • Sand –  .21 minute
  • Sod/Plants –  .53 minute

As the rain fell upon our ‘land’, we observed the formation of rivers, canyons and even waterfalls.

Conclusion ::

As we discussed the results of our experiment – comparing the water turbidity / clarity in the jars and the amount of sediment – we also made note of things that could have affected the outcome and made a list.

  • we didn’t have 4 boxes – and had reused one box with the sod (even though it was wet)
  • the dirt box was bigger and therefore there was more ‘land’
  • the sod was wet from the morning sprinklers and couldn’t absorb anymore water whereas the dirt we’d used (as well as the clay and sand) was dry