Soils Investigation #2 - Particle Size

Objective: To determine the flow rate and water retention capacity for different soil types.

Purpose: To understand the effect of particle size on flow rate and water retention

Part One:  Write your hypothesis

• Manipulated Variable: Particle Size (Soil Type)
• Responding Variable: Drain Rate
• Controlled Variables: Amount of soil, amount of water

Part Two: Write your hypothesis

• Manipulated Variable: Particle Size (Soil Type)
• Responding Variable: Water Retention
• Controlled Variable: Amount of soil, amount of water

Equipment: Graduated Cylinder, Funnel,Filter Paper, Beaker, Sand, Silt, Clay, Timer

   

Procedure

1. Measure 40 ml of water in the graduated cylinder. Pour into the beaker and set aside.
2. Fold the filter paper in half, then in half again. Place into the funnel and fold open.
3. Place funnel into the Graduated Cylinder
• First trial is filter paper only- pour water through and record
4. Measure two LEVEL teaspoons of sand and place into the filter paper funnel
5. Record observations of initial conditions
6. Pour the water from the beaker into the funnel so it will flow through the soil into the cylinder. Make sure your water does NOT rise above your filter paper.
7. Start the timer as you start pouring. Try to pour at a consistent rate and make sure the water is always above soil.
8. Record the amount of water in the graduated cylinder at prescribed times
9. Repeat for the other types of soil. Get a new piece of filter paper for each trial.

  Observations:

Note the appearance, texture, composition of your soil samples before and after each trial.  Ensure you break up the used sample to observe the interior as well as the exterior at the end of each trial.

Calculations

Calculate the water retention: how much water was left IN the SOIL at the end of your trial?

•  Water Retention = 40 ml – (water in graduated cylinder) – (water in filter paper) – (water still in beaker after 8min)

Graphing and Analysis

1. Graph your data – create a volume vs time graph for all four trials. Use different colors or symbols for the different trials
2. Describe the relationship show on your graph from each trial.  
3. Were any results surprising to you? Explain.
4. Why did you do a trial with filter paper only?
5. Do you think this is/is not a controlled variable? Explain your reasoning?

Conclusion

Write two conclusions

• Relationship between particle size and flow rate
• Relationship between particle size and retention

Application

• Which soil type do you think is best for farm land? Explain your reasoning.
• Provide one example each for where you think clay rich, sand rich and silt rich soil would be useful