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7th Grade Soil Science Unit Plan

Unit Summary:

In this unit, students explore the components of soil, soil making processes, the profile of soils in various locations, permeability of soil, types of organisms that live in soil and their role in soil building, consequences of poor soil management, climate and soil connections and finally desertification and our role in preserving soils.

Key Understanding (AAAS 2061):

  • Although weathered rock is the basic component of soil, the composition and texture of soil and its fertility and resistance to erosion are greatly influenced by plant roots and debris, bacteria, fungi, worms, insects, rodents, and other organisms. 4C/M6
  • The earth's surface is shaped in part by the motion of water (including ice) and wind over very long times, which acts to level mountain ranges. Rivers and glacial ice carry off soil and break down rock, eventually depositing the material in sediments or carrying it in solution to the sea. 4C/M2b*\
  • Sediments of sand and smaller particles (sometimes containing the remains of organisms) are gradually buried and are cemented together by dissolved minerals to form solid rock again. 4C/M3
  • There are a variety of different land forms on the earth's surface (such as coastlines, rivers, mountains, deltas, and canyons). 4C/M8** (BSL)
  • The world contains a wide diversity of physical conditions, which creates a wide variety of environments: freshwater, marine, forest, desert, grassland, mountain, and others. In any particular environment, the growth and survival of organisms depend on the physical conditions. 5D/M1b*
  • If a disturbance such as flood, fire, or the addition or loss of species occurs, the affected ecosystem may return to a system similar to the original one, or it may take a new direction, leading to a very different type of ecosystem. Changes in climate can produce very large changes in ecosystems. 5D/H2*
  • In all environments, organisms with similar needs may compete with one another for limited resources, including food, space, water, air, and shelter. 5D/M1a
  • Interactions between organisms may be for nourishment, reproduction, or protection and may benefit one of the organisms or both of them. Some species have become so dependent on each other that neither could survive without the other. 5D/M2*
  • Human beings are part of the earth's ecosystems. Human activities can, deliberately or inadvertently, alter the equilibrium in ecosystems. 5D/H3
  • Human activities, such as reducing the amount of forest cover, increasing the amount and variety of chemicals released into the atmosphere, and intensive farming, have changed the earth's land, oceans, and atmosphere. Some of these changes have decreased the capacity of the environment to support some life forms. 4C/M7

Week 1

DAY 1

ELICIT: What is soil? What is dirt? Give each table a container of soil. Ask the question, "What is in the bowl?" Invariably some students will say soil and other dirt. Ask them to tell you what it is. Take a selection of responses.

ENGAGE: Do Now:  Journal Activity: Students response to open ended question: What is Soil? Give students five minutes to respond in writing.

Small group share: Students share responses with their tables (8 min) and summarize ideas.

Large group share: Groups share summary responses and teacher records on chart paper. Keeps this posted for the remainder of the unit.  (12 min)

EXPLORE: Soil Profile investigation: (30min)

Give each table one of five different soil samples that correspond to five different soil profiles from different landscapes. These could include:

  • edge of river or shoreline
  • farm land
  • steep hillside
  • forest
  • hill top

They work in groups to make three observations, raise two questions and make one inference. Observations should include drawings and notes. The five soils profiles will be posted on the board and explained before the observations begin (percentage of each substrate only, not location)

Materials:

Hand lenses, Metric rulers, Soil column samples (3 ft long tubes), Journals

EXPLAIN: Groups will present their soil column sample observations and identify which profile they think they were given and the evidence they collected to make this claim.

ELABORATE: HW: In your journal: What can you infer about the location from where you soil core originated and the type of organisms that this soil may have supported(plants, micro-organisms, animals).

DAY 2

Finish sharing soil column sample observations if needed. (10-15 min)

EXPLORE: What’s on the horizon?

Students will label and identify the characteristics of different layers of a given soil column and compare to other types of soil.

To the students: Each layer is separated by horizons. Each horizon has distinct properties. Go back to the soil columns and identify where the boundary between each layer is located. Measure the depth and label each layer and create a table in your journal to record your group’s observations of the material, grain size/texture organic matter, color, structure. (25 min)

(Student handout)

Soil Core- Field Observations/Measurements/Data

Horizon #

Depth (cm)

Description(Grain size/Texture, Material, Structure)
   
   
   
   

Materials:Hand lenses, Metric rulers, Soil column samples (3 ft long tube), Journals

After students have shared their observations, label each section (O, A, B, C) and explain the general characteristics of each layer.

Soil Presentation ppt

EXPLAIN: Discussion: What do these observations tell us about the climate, topography, parent material, vegetation, age of soil, of where this soil formed. ? (20 min)

ELABORATE: Respond to this prompt when finished:  If soil horizons can be compared to tree rings then examining soil horizons could inform us about…

EXTEND: Some suggestions to facilitate group discussion

• Are there basic differences in the way the groups describe soil characteristics?

 What where the differences and the resemblances in the descriptions?

• What effect does a certain characteristic have on plant growth?

• What are the implications of these characteristics for crop growth (root development, nutrient availability, etc.)?

• What effect do such characteristics have on water management and erosion?

• Have farming practices changed, affected soil physical characteristics?

• What are the implications of these characteristics for soil management?

EVALUATE: HW: Choose one of the following locations and infer what the soil profile would be.  Rainforest, Tundra, Hot Desert, Farmland.

Follow up questions to HW: Are there differences in soil characteristics which can be related to location?

• What kind of soils can be found close to a river, or on a slope, or under a forest?

• How may soil type and its location influence the selection of the crop to be planted and soil/water management practices?

DAY 3

ELICIT: Do Now: Summarize what we know so far. What factors are needed for soil formation? Make a list in your journal. (5 min)

EXPLAIN: Feedback: All group share of ideas. Record on poster paper and compare to initial ideas. (10 min)

EXPLORE: Soil Mapping. Given a topographic map with a variety of landforms (hill top, delta, plain, riverbed, hill slope) and corresponding soil profiles (with % of each type of stratum) students will identify the elevation of each location and match the type of soil profile that would be found at each location. (20 min) (NOTE: Topo Mapping lesson can be introduced here, but mayl need to allow for a few more days or teach prior to this lesson)

Part 2. They will create a cross-cut drawing of the topo map and identify the location of each soil site. (20 min)

ELABORATE: HW: Predict the erosion rate and water holding capacity of soil in each of these locations. Explain your reasoning.

DAYS 4-5

ELICIT/ENGAGE: HW: Review What is Soil? Response from Day 1. How have your ideas changed? Write 4-6 sentences explain what you thought then compared to what you think now. Cite the evidence from our investigations in your response.

EXPLORE: Permeability Lab:Part 1

QUESTION FOR INVESTIGATION: How does the percentage of sand in a soil sample affect the rate of water permeability?

Given a column of sand and other material (clay), students will run three tests calculating the rate at which water passes through the column.

Group 1 :  0% Sand

Group 2: 25% sand

Group 3: 50 % sand

Group 4: 75% sand

Group 5: 100% sand

Materials: For each group of 3-4 students; Plastic, clear cups with a premixed amount of sand and clay, Beakers, 100 ml Water, Timers, ring stand, Graduated cylinders.

Procedure: Students are to run three trails to calculate the rate at which a given amount of water will drain through a mixture of sand and clay and compare the average time of their trials with other groups in order to make a claim on how the volume of sand affects permeability of soil.

ELABORATE: Part 2: How does water permeability compare between landscape positions of soil?

Using the soil profiles from Day 3 and the corresponding % of stratum in each, students will construct an experiment to test the permeability of their soil sample. They will begin by making a layered mix of material that is similar to the soil core sample. They will follow a similar procedure as the day before (repeated experimentation, share results)

Materials:Plastic, clear cups, Sand, Clay, Potting Soil, Rock, Compost, Gravel, Beakers, Water, Timers, Graduated cylinder

EXPLAIN: Groups will share their data on the board and then clean up their testing area. Follow up questions:

  • What do you notice about the permeability of your soil sample compared to the other groups? How do you think this might compare to the actual soil core?
  • What explains the difference in results?
  • How could knowing the drainage rate of soil help in land conservations and farming?

EXTEND: HW: How would the water retention of your soil sample affect plant growth in that location? What would you predict this landscape to look like?

Week 2

DAY 1

Summary: Last week we learned about the factors that are necessary for soil formation and compared the structure of soil from different locations and how permeable soils are based on their composition. This week we will turn our attention to the how soils support life and the importance of soil management.

ELICIT/ENGAGE: What kind of life does soil support? (Take 3-4 minutes and record in your journal the types of organisms that soils may support. A list is fine.

Last week we observed that the majority of organic matter was in the O horizon. Let’s take a closer look this week.

EXPLORE: Soils alive (47 minutes) What evidence of life can you find in the O horizon of soil?

Materials: Soil core samples (one form garden and one from less vegetated area), Hand lenses, Microscopes, Stereo microscopes, Metric rulers, Tweezers, Specimen dishes

Procedure: Give each table a 6 inch soil core sample taken from the school grounds. Using the tools provided, make observations of the sample and find evidence of micro and macro organisms. What sorts of microorganisms might exist that you cannot see?  How did the two sample compare? What can you infer about soil composition over time and the variety of life it is able to support? (Classify and organize specimens.)

EXPLAIN: Class summary: What did you observe? What questions do you have?

ELABORATE: What role do you think these organisms play in managing the soil? What conditions must the soil have in order to support these organisms? Under what kinds of conditions would they cease to survive?

DAY 2

Lessons from the Dust Bowl

ENGAGE: Given climate data and images of American prairie lands prior to, during and after the Dust bowl, students will make observations of the vegetation, soil conditions, weather phenomena. (30 min)

Materials: Images of the prairie lands, prior to, during and after the Dust Bowl, journals

Time PeriodObservations: Vegetation, Land, Climate
Prior to 1930 
1930-1940 
Post-1940 

EXPLAIN: Group Share: What did you observe? What questions do you have? What was happening to the soil in these different time periods?

The Dust Bowl[slideshare id=660164&w=425&h=355&sc=no]
View more presentations from montathomas

Presentation on the Dust Bowl

EXPLORE: Organic Farming: Conserving Topsoil Teacher's Domain

EXPLAIN: Discussion Questions

  • What impact do various farming methods have on soil quality and erosion?
  • What are the positives and negatives about farmers growing one crop in an area year after year?
  • What does manure do to promote soil fertility and moisture? Is all manure organic?
  • Are there areas of the world that are experiencing loss of vital resources such as soil, forests, and potable water? Where are they? Should the U.S. government assist these countries? If so, in what ways?
  • Could a dust bowl occur today? Explain.

(PPT: farming and soil mgmt. practices, westward expansion)

EXTEND: HW: Soils around the world. Students will read a short essay from Teacher's Domain on soils around the world and answer the following questions:

  • What are some key factors that influence the composition of soils around the world?
  • From studying these images, can you infer some of the processes that have formed particular soil profiles?
  • What are some of the characteristics of soils in the United States and how do these relate to the kinds of vegetation occurring on them?
  • Why is it important to know the soil structure of a particular area? Give several reasons.
  • What types of soil are in your area?

DAY 3

ENGAGE: Prediciting Future Desertification: Map comparison activity

Each table group will be divided into 4-5 small groups and given maps to analyze (Current and projected Population densities , Climate (Temp/Precipitation) Change forecasts, Current agricultural zones, Agricultural practices map, Soil Moisture/Temperature) (15 min) MAPS

  • What is the name of the this map? What does it show?
  • What patterns do you notice? Where in world are there similar conditions?

EXPLORE: Students will reassemble into lab groups and share with their group the maps they studied and the observations and inferences made.

Researchers have measured the degradation of the planet's soil using the Life Cycle Assessment (LCA), a scientific methodology that analyses the environmental impact of human activities, and which now for the first time includes indicators on desertification. The results show that 38 percent of the world is made up of arid regions at risk of desertification.

EXPLAIN: Predict areas on a blank map that are at risk for desertification. Once you have completed your predictions, obtain a map showing the regions of the world that are at risk and compare to your predictions.

  • How accurate were your predictions?
  • What data from the maps did you use to make your prediction.
  • What are the population densities in these regions?
  • What kind of impact would desertification in these regions have on these populations?
  • What do you think are the greatest contributors to desertification in these regions. Be specific.

Reference: http://www.sciencedaily.com/releases/2010/02/100209183133.htm

Day 4-5

Healthy Soil, Healthy Land

Goals: Students will conduct an investigation to better understand the cause-and-effect cycle of soil health, including the local and global effects of pesticides, toxins, and other soil pollutants.

Time Required: 40 minutes, plus research time

Materials: "Healthy Soil, Healthy Land" student reproducible, research materials, pen/pencil, supplemental information about soil (below)

Healthy Soil, Healthy Land (PDF)

Before Class Begins

Before students arrive, review the supplemental information about soil (below), including the environmental facts, conservation ideas, and real-world example showing the importance of soil health.

Background Discussion

1. Ask: Do you think you have a personal responsibility to help keep our local environment healthy? If not, whose responsibility is it? Engage students in a lively discussion about the importance of caring for the environment. Discuss whether a healthy environment is the responsibility of individuals, governments, private businesses, nonprofit organizations, or everyone on earth. Ask if students consider themselves to be "polluters," and remind them that cars, home heating/cooling systems, waste, and even hairspray puts foreign particles (pollutants) into the air.

2. Ask: Do you think our local environment is healthy? What parts of our environment do you think we could study to try to find the answer? (Clues to the health of an environment can be found in its air, water, plant and animal ecosystems, and soil. Highlight the fact that although all of these factors are very important to a healthy planet, soil pollution heavily influences the health of every other part of the environment.)

3. Explain that when soil is polluted, the entire ecosystem suffers. Make a list on the board of ways that contaminated land and soil affect plants, animals, and humans, including:

• food shortages: Soil pollution reduces the amount of nutrients in the soil, making it difficult for farmers to grow enough food to meet demand. Americans and people around the world rely on "America's Breadbasket" for grains, produce, and other products to survive. Contaminated soil could lead to massive food shortages.
• toxic atmosphere: Polluted soil cannot produce the nutrients that plants and trees need to survive. Plants and trees remove carbon dioxide from the air, leaving behind the clean, oxygenated air we need to breathe. If contaminated soil reduces the number of plants and trees, carbon dioxide in the air could rise to toxic levels.
• mass extinctions: Contaminated soil cannot produce the nutrients that plants need to survive, so the animals that depend on the plants for food will starve.
• water contamination: Rainwater that drains across contaminated soil before arriving in lakes and streams could contaminate drinking water.

4. Discuss how waste management and recycling are two of many ways to help reduce soil contamination. Use the supplemental information (below) to answer any remaining student questions about the importance of keeping the soil clean.

Using the Student Reproducible

1. Separate students into groups of 5 to 8. Explain that each group is going to present a persuasive argument about the cause-and-effect cycle of soil health. Students will develop a hypothesis, conduct an investigation to discover the facts, and then inspire others to act.

2. Instruct each group to choose a specific human action that could lead to soil contamination. Each group should then decide what it thinks the primary effect of that action will be (e.g., human actions like poor waste management, deforestation, and the use of pesticides can lead to effects such as soil erosion, animal and plant extinction, and food shortages).

3. Distribute a copy of the "Healthy Soil, Healthy Land" student reproducible. Student teams should use this reproducible to help guide their research.

4. Provide class time for students to research and present their findings.

5. Take a class poll to find out which group had the most compelling argument for action! Discuss what was most persuasive about each presentation.

Special Project (optional)

Challenge students to make a difference in the health of their local land! Help student teams create and implement a "Protecting the Land" Action Plan for a chance to win more than one million dollars in scholarships and grants!

Here's how it works:

• Choose a topic: Help each student team choose one of the following areas of soil health to focus on:

a. Waste management and recycling
b. Deforestation
c. Endangered animals

• Research: Provide class time for each team to research its topic.
• Develop a plan: Instruct each team to create an original plan describing what it wants to do to help keep the land healthy. Each team should  complete the online Action Plan to describe its incredible idea!
• Take action: Guide each team as it implements its Action Plan. Remind students to keep track of any successes and challenges throughout the process.
Special Project Example

Review this sample idea with students to help them get started on creating their own amazing Action Plan!

Topic: Endangered animals

Research: Student teams research four endangered animals in four different areas of the United States. They discover how each animal has become endangered and why the potential loss of these animals will affect the entire U.S. and the world at large.

Action Plan: Student teams host an eco-awareness event at their school to share information about what everyday people can do to help endangered animals.


SUPPLEMENTAL MATERIALS: SOIL HEALTH


FACTS ABOUT SOIL

Reinforce students' understanding of soil and how it affects environmental health by sharing the following questions and answers:

• Why is healthy soil important?

o The products that drive our economy rely on healthy soil to succeed (e.g., produce, textiles for clothing, grazing land for livestock).

o Healthy soil also influences the health of other natural resources, including water, air, wildlife ecosystems, and plant habitats.

• What is "healthy" soil?

o Healthy soil is filled with microorganisms that filter and replenish the nutrients in the soil in a continuous cycle. This cycle also filters harmful pollutants out of the soil by processing the waste.
o Healthy soil is pesticide-free, so when rain or snow falls and flows into rivers and lakes, water supplies remain clean.

• What causes soil to be "unhealthy"?

o Soil contamination comes from pesticides, factory pollution, unwise farming practices, and waste.
o Waste: The United States produces 230 million tons of personal, commercial, and agricultural waste each year. Landfills are unable to keep up with the demand, leading to contamination of soil and water supplies.
o Deforestation: Trees are nature's filter. They remove air pollutants and drive the air-recycling process that produces clean oxygen. Deforestation also leads to soil erosion and landslides, and disrupts the composting cycle that nourishes the soil for other organisms.
o Tropical rain forests are home to 50 to 90 percent of all organisms on earth, including 90 percent of all primates.
o 50 million organisms can survive only in the rain-forest ecosystem.
o Rain forests are the source of 25 percent of all medicines.

• What does unhealthy soil influence?

o Animal and plant life
o Ecosystem health
o Water quality
o Air quality
SOIL CONSERVATION
Share some great ideas with your students about how they can help to keep the land healthy! Reinforce the importance of thinking both locally and globally. Local plans are often easier to implement, but global plans can reach a much wider audience.

• Wise waste management:

a. Composting: In nature, fallen plants and animals decompose naturally. Composted waste is gradually processed and cleaned by soil, providing fresh nutrients for plants and animals.
b. Preventing waste: When people make a commitment to using durable, reusable items and purchasing products with less packaging, they are reducing the amount of waste they produce.
c. Incineration or burning waste: Used wisely, incineration can produce steam, which is processed as electricity.
d. Recycling: Using recycled materials reduces the amount of greenhouse gases and pollutants that are put into the environment by traditional manufacturing plants. Recycling also conserves fossil fuels, saves energy, and reduces waste.

• Pesticide-free farming: Encourage farmers to "go organic" and use pesticide-free fertilizers to keep contaminants out of the soil.
• Prevent erosion: Plant a windbreak of trees or bushes around fields to reduce the chance that wind will blow the topsoil away into your water supply. Planting trees at water lines (like rivers and lakes) helps prevent erosion of the banks into the water bodies.


THE DUST BOWL: REAL-WORLD EXAMPLE

Illustrate the importance of healthy soil by discussing the Dust Bowl (1931–39) and how it led to the Soil Conservation Act of 1935.

Explain that during the Dust Bowl, dry topsoil began blowing off farmland all across the United States. Without topsoil, farmers were unable to grow enough food and the agricultural economy collapsed. It affected not only the human population dependent on the crops but also the plants and animals that relied on the nutrient-rich soil to survive.

Review the following sequence of events with students:

a. In 1931, the United States entered into a drought that lasted until 1939. Crops across the country died in the fields.
b. As farmers tried to farm dry land, they realized that excessive grazing and plowing had disturbed the natural soil-replenishment cycle. Dust clouds began to blow across the Midwest in 1932.
c. By 1934, dust storms covered 74 percent of the United States.
d. The government tried to correct the damage to the overused soil but wasn't able to. According to the 1934 Yearbook of Agriculture, "Approximately 35 million acres of formerly cultivated land have essentially been destroyed for crop production. . . . 100 million acres now in crops have lost all or most of the topsoil; 125 million acres of land now in crops are rapidly losing topsoil."
e. In 1935, soil erosion was declared a "national menace" and farmers were paid to use soil-conservation farming methods such as strip cropping, terracing, crop rotation, contour plowing, and cover crops as part of the Soil Conservation Act.
f. By the end of 1935, 850 million tons of topsoil had blown off the southern American plains.
g. By the time it began to rain again in 1939, food riots and economic hardship had taken a harsh toll on the United States and the world.

EXTENSIONS:

  • SCHOOL GARDEN CONNECTIONS
  • WORM BIN STUDY
  • MUDDY RIVER (FIELD STUDY)
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