EDD Proposal


Experimental Design Diagram: pH level change in soil over time

        

  1. My question:

How does the pH level in the soil change over time?


  1. Research:


Works Consulted

Gibson, Mary Jo. “Understanding Soil pH.” Penn State Extension, 28 June 2023, https://extension.psu.edu/understanding-soil-ph. Accessed 6 September 2025.

United States Department of Agriculture. Inherent Factors Affecting Soil pH Soil pH Management, May 2014, https://www.nrcs.usda.gov/sites/default/files/2022-10/Soil%20PH.pdf. Accessed 6 September 2025.


There are various influences that cause effects on the pH levels in soil including the texture of the soil, the climate, time of formation, and much more. In wet warmer climates pH levels will likely go down over time due to precipitation, but in dryer areas the pH levels may very well stay the same. Soil containing clay often takes longer to change in pH level while soil with sand is faster. The pH level is also affected by the number and type of plants around and in it. Places with more trees are usually more acidic. PH levels are basically just measuring how acidic or non-acidic something like soil is. Nitrogen and sulfur fertilizers can lower the pH levels in the soil over time as well. 


  1. Hypothesis: 

    1. If I track the pH levels over time, then the pH levels will stay largely the same, but will go down slightly, because the piece of land contains quite a few plants, which causes the soil to be quite acidic, and the land is relatively warm and wet, which causes the pH levels to go down.  The rain will drain down towards the pond, so it is likely that the pH levels will drop somewhat, especially if it is a rainy fall. 


  1.  Data Table 


  1.  Controlled Variables

  • The exact same extraction points.

  • The exact same extraction depth. 

  • The extraction will be about the same time consistently. (about every two and a half weeks)

  • The same type of pH measurement will be used each time.

  • I will make sure that there are no external materials on the testing probe or in the hole.


  1. Materials:

I will need a pH probe that I already own, as well as a pencil and paper that I need to write the information on.


  1. Procedure


  1. Take a well calibrated pH probe just like the one shown in the picture that you can stick into the ground.

  2. Go to my location.

  3. Go to the ground that is located directly between the rock by the pond and the pond itself that has an X over it.

  4. Clear away any debris that may be in the way down to the soil. Just brush away any debris like leaves with your hand.

  5. Stick the probe into the ground at about 3 inches deep that is located directly between the rock by the pond and the pond itself.

  6. Look at the measurement, and check it a couple times to make sure it reaches a constant point. Once it has not changed for about a minute it is good to take the value.

  7. Then do the same test five times to ensure that there is low to no margin of error. 

  8. Take each pH level and write it down in the data table.  Average the five measurements on that day and write down that average. 

  9. Repeat this experiment about every two and a half weeks five times.

 

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