Soil pH Tests

Follow up from the pH investigation.

Whilst in the woods on Monday 15^th of April our group decided that we could try and measure the pH levels within the soil around certain trees. This experiment was carried out to investigate whether or not the acidity levels in the soil would differ from tree to tree within a fairly localised area.

The key questions we wanted to be able to answer form this experiment were:

1.     If the acidity level within the ground would change from plant to plant and from tree to tree?

Here are the answers we found for the question.

We looked at three different trees/ plants and took two measurements of the soil from different sides of the plants to make the test fairer.

We used barium sulphate  (this is used to help separate the soil grains so the soil goes into suspension) and pH indicator solution to determine the pH of the soil. We did this by:

1.     Digging a small amount of soil around the plant and putting this into a test tube.

2.     We then added the barium sulphate ( one spatula).

3.     After the powder had settled, we added distilled water to the test tube to fill it to half way.

4.     We then added 10ml of pH indicator solution.

5.     We shook the test tube and left to settle.

This particular sample of soil was taken from a cherry laurel. This was the less acidic than the black thorn and less alkaline than the lime tree so we decided as a group to give this a 7.0 on the pH scale.

This sample came from a Black Thorn. This was the only acidic soil we found whilst taking our six samples throughout the woods. As a group we decided to give this a 5.0 on the pH scale.

This is a sample of soil taken from the bottom of a lime tree. This was the most alkaline of all of the soils tested. As a group we decided that this was a 7.5 on the pH scale.

The measurements that were taken twice as to give a more accurate representation of the pH levels within the soil around the plants. We did this because the soil around the forest is very chalky and we did not want this to have a noticeable impact on the pH levels.  We also did this test twice to make sure that the results were accurate with each other, as you can see from the 3 photos that have been taken, both tubes in all three photos are similar in colour even though they were taken from slightly different patches of soil. This shows that our results were more accurate.