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Soil and Water-Holding Capacity

Max Strain
Heritage Elementary School
1700 E. Pawnee
Olathe, Kansas 66062

Overview: This lesson will help students gain an understanding of the relationship between organic matter in the soil and water holding capacity. Normal field soil water- holding capacity is 60-80% of its total capacity; that is 60-80% of the water filled pore spaces are filled. This corresponds to the optimal biological activity of 60-80% of the water-holding capacity. When the water-holding capacity falls below 55-60%, organisms could suffer from dryness; and when the capacity is over 80%, they begin to suffer from a depletion of soil oxygen.

Grade Level: 6-9.

Connection to the Curriculum: This lesson is to be used in conjunction with a soil ecology unit that explores all aspects of soil use.

Time Required: The total time required including class discussion and follow up will be approximately two days.

Materials and Equipment: Soil samples (oven dried), Humid Chamber, Hilgard soil cups, Drying oven, Spatulas, Mortar and pestle, Triple beam balance, Filter paper.

Objectives: The student will complete a hands-on activity that will allow them to determine the water-holding capacity of soil. Each student will use the process of observation, classifying, exploring, recording, predicting, inferring, investigating, and valuing.

Procedures:

1. Place a moist Whatmen #2 filter paper on the screen inside the Hilgard soil cup. Weigh and record the cup dry with filter.
2. Prepare the soil sample by crushing it to a fine state using the mortar and pestle. (This will require soil that has been dried in an oven at 110 ^oC for 24 hours to remove all moisture.)
3. Fill the cup gently with oven-dried soil so that it is even with the lip of the cup. If necessary use a flat blade to obtain an even surface.
4. Place the cup into a shallow pan of water allowing only the bottom few cm of the cup to become wet.
5. Allow the soil to become saturated.
6. Remove the cup from the pan of water and place it in a humid enclosure until drainage is complete. Then weigh and record data.
7. Complete the data sheet to obtain the water-holding capacity of the soil sample tested.

Body of Presentation: This will work well with any lesson on soil and water capacity or use. It works well with previous soil lessons that may have required the drying of soils for other experiments. This will allow the students to use other predried samples from previous experiments rather than dry samples for this one particular exercise.

Assessment: This will be accomplished by the students completing a correct data information sheet used during the course of this experiment.

Lesson Extension: This lesson can be extended by using other soil types. Soils used for comparison can range from those in cities, construction sites, grasslands, and fields in and out of production. Charts can be used to compare various soils for water holding capacity.
 
 

			Soil A	Soil B
Weight of dry cup with wet filter			_______________	_______________
Weight of dry cup and dry soil			_______________	_______________
	Gross weight (same as above)		_______________	_______________
	Dry soil weight	_______________		_______________
Saturated soil and cup weight			_______________	_______________
	Minus weight of cup	_______________		_______________
	Weight of wet soil after draining		_______________	_______________
	Minus weight of dry soil	_______________		_______________
		Water (g)	_______________	_______________
		% Water holding capacity	_______________	_______________

From http://www-personal.ksu.edu/~jsherow/strain.htm

Permeability of Earth Materials

Al Musson
O'Neill High School (O'Neill, NE)

Background: The ability of a rock or earth material to transmit a fluid is known as permeability. The ease or difficulty with which the fluid will pass through is dependent upon the type of material. The size and spacing of particles in the material will directly effect the ease at which a fluid can pass through.

Objective: Demonstrate the apparent difference of the permeability of various earth materials.

Materials: Buckets of silt (loess), sand, gravel, clay, four 2-liter pop bottles, timer, ring stands, and beakers.

Procedure:

1. Cut off bottoms of bottles, drill hole in top cap and put a disc of screening in cap (this can be done ahead of time for the students).
2. Label and fill each bottle with a different type of earth material. Place the bottle in the ring stand as shown by instructor.
3. Predict what may happen in each bottle when the water is poured onto the dry material. Record your results in the data table below.
4. Add water to the bottles. Start timer and measure the time for water to pass through each material. Record this information in your data table.
5. Allow the water to drain from the bottle. Repeat the process with the damp material. Record the time for the damp material in the data table below.
6. Note any changes in the waters behavior between the dry and wet trials. Record your observations in the data table.

Data Table:
 
 

Type of Material	Prediction of flow	Time of flow-dry	Time of flow-wet	Changes wet vs. dry

Conclusion:

1.Water passes through ______________ in the least amount of time and passes through _______________ in the greatest amount of time.

2.Did the water not pass through any of the bottles? Explain.

3.Defend the suitability of establishing a landfill or waste storage facility in/on each column of earth materials.

DETERMINING AMOUNTS OF GROUNDWATER IN SOIL

By Mike Steinbrink
Class: Life Science
Grades 6-8 (All levels)
Approximate time to complete 2 weeks

TABLE OF CONTENTS

EVAPORATION

Topic: Evaporation using a constructivist approach
Grade: 6-8 (All levels)
Duration: 45 min.

Objective:  To discover how much water is contained in different soil samples.

Purpose: Soil contains a considerable amount of water which can, if not used by plants for evaporate, end up in the underground water supply. The finale of this group of lessons will be built upon using a constructivist approach to learning science. Students will first take samples and discover that the lost weight is indeed water. They will look at how water is stored in the ground and how it moves from one place to another. Then they will manipulate the actual underground movement of water in a model. These activities will culminate with the realization of water's importance to man.

Materials:

• Several containers for each group. (No more than 1/4 to 1/2 cup size.)
• Table lamps (to provide heat for evaporation), for each group.
• Scale.
• Science Logs. (Have students make or acquire a science log for these experiments.)

Activity:

Divide the class into groups of 4-6. Ask the following questions:

Does soil contain water?
How do you think that the water gets into the soil?
What does the water do in the soil?
How could we find out how much water is in our soil samples?

- Let students make suggestions to the entire class. Instructor should only listen and make positive comments or suggestionsm during this period. Once classroom discussion is complete (if not already done), let the groups make a column for the following:

Weight of container.
Weight of container and soil together.
Weight of container and soil minus weight of container.

Now explain that they need to determine the weight of the soil in the container today and again in a few days (at least 2). have students place lights over their soil samples. Make sure that students set their lights about 5 mm above the soil. (It is important to make sure soil is totally dry.)

Proceed with next 2 experiments while soil dries.

Conclusion:

Look at overall class participation and add any help necessary for every student to achieve success.

Evaluation:

Use the following rubric:

4 = Group participation and oral responses relating to topic.

3 = Some group participation, mostly clear on concept from oral responses.

2 = Little group participation, oral concepts mostly unclear.

1 = No participation, no idea of concept being learned by group.
 

Topic: Water storage using a constructivist approach
Grade: 6-8 (All levels)
Duration: 45 min.

Objective: To discover how much water is held onto by soil.

Purpose: Soil can and does hold onto water particles which allows for ground water storage. The purpose of this lesson is for students to determine how much water soil holds onto.

Materials:

One container with holes in bottom for each group. (No more than 1/4 to 1/2 cup size.)
Container for holding water.
Graduated cylinder.
Scale.
Science Logs.

Divide the class into groups of 4-6. Ask the following questions:

How many of you think that soil contains water?
What is the benefit of water being in soil?
How could we conduct an experiment to see how much water is in a soil sample if we were to add a determined amount of water?

- Let students make suggestions to the entire class. Instructor should only listen and make positive comments or suggestions during this period. Once classroom discussion is complete (if not already done), let the groups make a column for the following:

Amount of water in graduated cylinder.
Amount of water left after pouring it through soil.
Weight of soil.

     What happened to the extra water that did not come out the other end?
     How would we figure out how much water has been retained by our soil sample?

Let students discuss in groups their ideas of how to find out the amount of water left in the soil. Let groups share their ideas with
the class. Lead this discussion if necessary.

Now have students weigh their soil samples and place under their already burning lights to dry for 2 days.

Conclusion:

Look at overall participation and add any information necessary for all students to achieve success.

Evaluation:

Use the following rubric:

4 = Group participation and oral responses relating to topic.

3 = Some group participation, mostly clear on concept from oral responses.

2 = Little group participation, oral concepts mostly unclear.

1 = No participation, no idea of concept being learned by group.
 

http://www.dri.edu/Admin/1995_teachers/steinbrink.html

by Kimberly Flessner
Norfolk Catholic High School
Grade Level:  Intermediate - 8th grade
 

Objective:  The students will be given several types of soil to test how   water permeable each type of soil is.

Materials:

3 tin cans with the bottoms cut out
fine screening
different types of soil
gravel
sand
clay
black dirt
duct tape or some other type of clamp
6 - 250 mL beakers
magnifying glass
plain white paper

Each group of students should collect 3 pieces of plain white paper and samples of three different types of soil.  Place each types of soil on a piece of paper and look at the texture and color of the soil.  Record this information in a data table. After observing the three soil types each student should make a prediction of which the water will run through the fastest to the slowest. Prepare each of the three cans by duct taping the fine screening to one of the open ends of the can.  Into each of the three cans place about 2 inches of the three different types of soil. Holding one of the cans with soil in to over a 250 mL beaker pour 200 mL of water into the soil and collect how much water will run through it in 1 minute.  Then after 5 minutes see how much water has moved through the soil. Repeat with the other 2 types of soil.

Conclusion:
 

1. How did your predictions compare with the results?
2. Which of these soils would be the best to use of drainage  material?
3. How does the texture of the soil compare to its water permeability?
4. Do you think your results would change if you packed the soil into the can?

Data Table:
 

Soil Type	Soil Texture  & Color	Predicted Permeability	Amount of water after 1 minute	Amount of water after 5 minutes

 

Objective: This activity will help you understand that water moves through different types of soil at different rates. The movement of the water depends upon the soil's porosity and permeability.

Materials: ring stand, funnel, cotton balls, large beaker, (2) 100 ml graduated cylinders, 4 different types of soil, water, pencil.

Procedure:

1. Set up apparatus so that ring stand is supporting funnel (a clamp or ring may be used to hold funnel in place). There should be ample room beneath the funnel for the large beaker to fit.
2. Place a cotton ball in the small end of the funnel.
3. Using a graduated cylinder, measure 100 ml of soil #1 and place it in the funnel, on top of the cotton ball.
4. Place the beaker underneath the funnel.
5. Using the other graduated cylinder, measure 50 ml of water and dump it into the funnel. Let the water percolate through the soil and collect in the beaker for 3 minutes only!
6. Measure the amount of water in the beaker and place this number in data table #1.
7. Clean apparatus, placing the used soil in the designated area. Then, repeat steps 2-6 for soil samples 2-4. Record all data in data table #1. Be sure to complete questions.

DATA TABLE #1
 

	water amount added to soil	water amount in beaker (ml)	percentage of water in soil
sample #1
sample #2
sample #3
sample #4

Questions:

1. Using your text, define porosity and permeability.
2. In which of the soil samples did the water percolate the quickest? Why did this happen?
3. In which of the soil samples did the water percolate the slowest? Why did this happen?
4. Using the dissecting scope, observe the 4 soil types on low power. Sketch what the soil particles look like in the space provided. sample #1 sample #2 sample #3 sample #4