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Effect of juniper trees and limestone on soil pH

Ellen Buening and Cassidy Ragains

Introduction

14 of 17 essential plant nutrients are obtained from the soil.  A pH range between 6 and 7 is the best for plants to obtain nutrients from the soil.  Higher acidity of soil may be caused by presence of conifers, rainfall and leaching, acidic plant material, high rates of organic matter decomposition, and crop harvesting.  High limestone content in the bedrock can increase the soil pH to more basic levels.

hypothesis

Soil will be more acidic underneath junipers and will be less acidic 5 to 10 meters from junipers.

methods

We collected data from two sites, A and B.  Site A:  3 samples with juniper, 5 samples without juniper.  Site B:  4 samples with juniper, 4 samples without juniper.

We collected soil samples from randomly chosen spots.  The soil pits were 2 inches in diameter and 5 inches deep.  Soil samples were stored in plastic bags.  In the lab, we tested pH of the soil samples and used sieves to separate the soils by particle size.

results

There was no difference in the pH of soils between areas with junipers and areas without junipers.  There was also no difference in the pH of soils between sites A and B.  There was a difference in the color of soil between sites A and B.  The soil from site A was yellowish, indicating presence of iron oxides.  The soil from site B was darker and blacker, indicating presence of manganese oxide and high organic matter content.

discussion

The soils in the Nature Park have a high content of limestone.  The limestone may be counteracting the acidity of the junipers.  Soil in this part of the Nature Park may be well buffered from acidity.

Future studies could look at soil pH levels in other parts of the Nature Park.  Larger sample sizes could be collected to further test our hypothesis.  Future studies could also test for presence of specific ions and nutrients, such as manganese and iron oxides that may be influencing the soil color.

references

Ball, J.  2014.  Understanding and correcting soil acidity.