Experimental Design - Soil pH

My question: Will the location on my plot affect the soil’s pH?

Hypothesis: If I change the location on my plot, then the pH will change because different types of soil have different pHs.  

Controlled variables are: The same amount of soil, same equipment used to test the soil, the soil is the same depth down from the surface, soil is stored in the same individual plastic bags and the water used to test pH is from the same source.

For my experiment, I’ll need 3 dirt samples from each different location, plastic bags to hold the dirt, a rolling pin to crush the soil, a screen to filter it, a spot plate, and duplex indicator.

Procedure: Go out to my plot with a small hand shovel, a hoe to scrape of surface objects (rocks, etc.) and 7 numbered plastic bags. I also went out with a map showing the #'s where I would be taking the soil samples. (shown below)

I went to each numbered spot on the plot and scraped off the surface litter. I then dug down with the small hand shovel. I dug down six inches below the surface, then dug more dirt out, but put it in the corresponding bag. I did this three times for each location, each within a foot of the location at the number. I put each sample of the soil into the same bag for that number and mixed them together.

 I did this for all 7 locations. Once I was done collecting each sample, I headed back to my house. Once I got there, I opened the bags so that the soil could dry out. Once the soil was dry, the soil was crushed. I couldn't find a screen, so I just tried to use the really fine pieces of dirt after removing the larger clumps and small pebbles instead of sifting through the soil. Once the small pieces were sorted out, I got out the spot plate. In the larger "well," I put enough small pieces of soil in to fill it about halfway. Then I added enough duplex indicator to dampen the soil. 

After a minute, I tilted the spot plate enough so that the indicator flowed into the small well. Then, I grabbed the pH color chart. The chart shows how to tell the pH because it shows the colors that the indicator will turn for each pH between 4.0 and 8.0.

I then matched the color of the indicator to one of the colors on the chart. I estimated if it was in between. I then put the results in the appropriate spot on my table.

1. By looking at the data table and the graph, I can see that the numbers differentiate quite a bit.  Location #2 obviously has a low pH compared to the other places on the plot. This was the spot by the grass clippings By the algae puddle on spot #4, the soil tested with the higher pH as did spot #7 in the soybean/corn field. The graph doesn't make much sense as a whole to look at, but the graph shows that the location matters because the soil pH's are very different. 

If I did the experiment again, I would dig the dirt when it was earlier on. This is because the soil was pretty much frozen and it really wasn't fun chiseling into pebbles and cold ground. Also, I would dried out some of the soil more. This is because I understood why you needed to dry it out completely when you put the soil in the spot plate. After you put the duplex indicator in, you don't want to see mud because you want to see the color of the duplex indicator. Other than that, I think that my experiment went well. In the future, I think I would test and see if the plants in each area change because of the pH. In each area that I tested, the plants were different, but I would like to know if this is just because of the pH or if other factors affect that. Also, I would  like to see how much pH changes throughout the year. I think that the ground is relatively "dead" in the winter because there aren't much plants that die and can be decomposed in the cold. Because there wouldn't be much decomposition, the pH would be higher. (The acids from decomposed organic material make the soil more acidic). The pH test measures how much hydrogen is in the soil. The "scale" goes from 0 to 14, 7 being the neutral point (pH of water). Carbonate molecules are a reason why some soil has a higher pH. The conditions that carbonates exist in are low oxygen and high carbon dioxide. Since most of the soil examples are above 7 (basic) that means that there is more carbon dioxide than oxygen. 

Soil usually has more acid if there is a lot of rainwater washing away things like calcium and other nutrients. Also, soil can be more acidic there is a lot of carbon dioxide. Decomposition and root respiration matter becomes acidic when it's dissolved in the water contained in the soil. Also, when organic matter decays, acids are formed, making the soil more acidic. We can see that some places on my plot definitely have more acid than others. Area #2 is the most acidic out of all of them. #2 was the soil samples taken under the grass pile. This makes sense because there was a lot of organic matter decaying (the grass) right above it. The decomposing grass is acidic and makes the soil more acidic. The most "basic" out of all of the areas that I sampled was #7. #7 was the area out in the soybean/corn field. This makes sense because they spread manure and fertilizer on the field quite often and the soybeans and corn (they do crop rotation) like the pH that it's at (about 7.5). It would make sense that the soil here isn't very acidic because there aren't plants in the field right now, so there can't be much decomposition of organic matter going on because there wouldn't be much to decompose. Areas #1 and #4 also have higher pHs. This makes sense for area #1 because there isn't much growing there (not much to decompose). #4 confuses me, though. Area #4 was the spot where there is the algae puddle. I thought that since there were a lot of dead plants and old grass clippings in the soil here that there would be more decomposition, creating a more acidic pH. However, this area has one of the higher pHs. I expected #3, #5 and #6 to have similar pHs. This is because these areas are relatively similar in characteristic. This is because each spot has a fair amount of plants that were about the same size and type. I also think that there would be about the same amount of decomposition because of the plant amount. (The same amount die and are decomposed). 

Sources: http://blog.calciumproducts.com/posts/you-have-high-soil-ph-now-what.cfm
http://en.wikipedia.org/wiki/Soil_pH
http://www.esf.edu/pubprog/brochure/soilph/soilph.htm
https://moodle.hollandchristian.org/pluginfile.php/99650/mod_page/content/6/soil%20pH%20test.pdf
https://moodle.hollandchristian.org/pluginfile.php/99650/mod_page/content/6/soil%20pH%20color%20chart.png