pH and Fertility Differences Between Mount Redoubt Volcanic Ash and Generic Potting Soil.

Samantha Shields

Samantha Shields
High School Grant-in-Aid, 2001
Holbrook High School, Holbrook, Arizona

Abstract

The purpose of this experiment was to perform different types of fertility tests on a sample of Mount Redoubt volcanic ash and a sample of generic potting soil. This was done to compare and contrast the different pH, phosphorous, potassium, and nitrogen levels found in each type of soil.

Each sample was tested and then recorded in a project data book. The results are as shown, the pH of both soils was 8.0, phosphorous level was low in the volcanic ash and medium in the potting soil, potassium level was medium in the ash and high in the potting soil, and the nitrogen level was low in both samples of soil.

Due to the limitations of the fertility tests used in this experiment, more accurate calculations could not be made. This meaning the actual levels of potassium, nitrogen, and phosphorous were not calculated in numbers as was the pH test. The results show that there is quite a difference between the levels of each compound found in the two types of soil.

Introduction

Soil is a very essential part of ecology because of its fertility and other attributes.

There are many different types of soil. The two that were used in this experiment were potting soil and volcanic ash, both, which are very fertile. The soils are composed of three different components, air/water, rocks/minerals, and organics. There are also three types of rocks/minerals that are found in soil. These are, sand, silt, and clay, all differ one from another in size. The project's objective was to find out if there was a difference between the pH levels and fertility levels between each sample of soil. The alterative hypothesis proposed was that there would be a significant difference in the pH and fertility levels between the two soils. The null hypothesis was that there would be no significant difference in pH and fertility levels between the two soils.

Experiment

First a pH level test was performed on each sample. A test tube was filled to its shoulder with distilled water, then one soil pH tablet was added, using the green test tube cap to measure one capful of the prepared soil was added. After this was done the tube was capped and mixed by inverting ten times. Let set for one minute and compared to a pH chart. Tested were volcanic ash and potting soil. Second was a test used to see if the soils have a high or low concentration of nitrogen, potassium and phosphorus. An extraction tube was filled with distilled water to the 30ml line, two Floc-Ex tablets were added, the tube was capped and then it was mixed until the two tablets dissolved. After this was done the cap was removed and a heaping teaspoon full of soil was added, the tube was capped again and was shaken for one minute then left to sit until the soil had settled. For the nitrogen test, a pipette was used to transfer the clear extraction solution above the settled soil to a different test tube until it was filled to its shoulder. One Nitrate #2 Tablet was added, the tube was then capped with the red lid provided and mixed until it dissolved, one Nitrate #2 Tablet was added the tube was capped again and mixed until it had dissolved. After five minutes of letting it sit a color had developed and was then compared to the pinkish chart provided with the test kit. For the phosphorus test a pipette was used to transfer twenty-five drops of the clear extraction solution to another test tube. Then the tube was filled to it shoulder with distilled water and one Phosphorus Tablet was added. The tube was then capped with the blue cap and mixed until the tablet dissolved. It only took five minutes for the color to develop and then was compared to the chart provided for phosphorus. For the potassium test the pipette was used again to transfer the clear extraction solution to the last test tube until it was filled to its shoulder. One potassium tablet was added and then the tube was capped with the white cap and mixed until it disintegrated, then the cloudiness of the solution was compared to the potassium color chart provided. The tube was held over the black boxes on the chart in the left column and compared to the shaded boxes in the right column.

Discussion

A t-Test statistical analysis was performed and the results are as shown in Table 1. The two samples of soil have a pH value mean of 8.16666667 and 7.3333333. Because of these results, the null hypothesis, which states that there is no significant difference between the levels of fertility and pH levels in volcanic ash and potting soil, was retained. This means the alternative hypothesis was rejected. The fertility levels were classified as low, medium and high. Since neither of the two soils had a high level of any of the three types of nutrients, Figure 1 shows the levels being medium or low. Two being medium and one being low. The three types of nutrients were Potassium, Phosphorous, and Nitrogen. The results as are followed potassium was medium in both soil samples, phosphorous was low in the volcanic ash and medium in the potting soil, the nitrogen level was low in the two samples.

See graph.

pH Data


Volcanic ash Potting soil
8 8
8.5 8
8 7.5
8 8

t-Test: Paired Two Sample for Means


Volcanic ash Potting soil

Mean 8.16666667 7.83333333
Variance 0.08333333 0.08333333
Observations 3 3
Pearson Correlation 0.5
Hypothesized Mean Difference 0
Df 2
t Stat 2
P(T<=1) one-tail 0.09175171
T Critical one-tail 2.91998731
P(T<=t) two-tail 0.1S350342
T Critical two-tail 4.30265573

Table I. pH statistical analysis results.



With the results from the information in the table above it was determined that the alternative hypothesis was rejected and the null hypothesis was retained. This is because the t-test computed a P(T<t) two tail value of .18350342 which is greater than 0.05. This means the difference between the means of the two soils is not significant.

As in any scientific research there were limitations to the experiments that were performed. For example the procedures for the tests were already laid out and did not allow personal modifications. Because there was no specific limitation to how many times a test could be performed the pH fertility tests were completed a total of four times to in order to obtain the most accurate results possible.

There are several factors that may have left room for possible inaccurate results. One factor may have been the amount of soil used in each experiment. Although the quantities of soil weren't exactly equal, slight differences could have had an effect on the final results. Different shaking speeds of the tablets and soils in the test tube could also have affected the end results. The results were uncontrollable for the environment for which they were provided. If this experiment were to be done over it would be best to do it in a controlled environment where there is not as much room for error.

Some future experiments could possibly be finding other types of fertility and pH variances in different soils. Another possibility might be to find out how much a certain soil has changed over the centuries.

Conclusion

In conclusion the volcanic ash pH values were found to be more acidic than the potting soil. A t-test statistical analysis of pH data allowed for the null hypothesis to be retained, it stated that there was no real great significance difference in pH and fertility level found between the two soils.

Acknowledgments

I would like to acknowledge Mr. Hurst, Mr. Stacey, Polly Barela, the Williams family, Nicole Graff, my mother Marci Shields for being there for me, everyone who contributed to my studies, and Four Corners Math and Science program.

References

Redoubt Volcano- http://www.avo.a1aska.edu/avo3/volc/redou/text.htm

Encyclopedia V. 1994. pages 462-466.