Soil pH and Plant Growth
Saskia Kirste-Yee
Sir Charles Tupper Secondary
Floor Location : J 129 D

The purpose of my experiment was to find out how acidic soil and alkaline soil affected the growth of plants. I selected three different types of plants: green beans, spinach, and radishes. I decided on these plants because they sprout quickly, as I wanted to be able to produce results as soon as possible. My hypothesis was that the plants would die slowly over the course of a week or so, because I know that plants generally don't grow very well in conditions they are not accustomed to. Before I began, I researched the ideal pH for each plant and how they were affected by acidic or alkaline soil. From this, I learned that green beans like a pH of 6.0-7.0, radishes like 6.0-6.8, and spinach a pH of 6.0-6.5. I also learned that in alkaline soils it becomes difficult for plants to absorb necessary acidic nutrients, and vise versa. I also learned that the aluminum in acidic soils interferes with the cell wall formation of a plant. When it came time to conduct my experiment, I first sowed a total of 27 seeds, nine of each type of plant, in plastic cups and allowed them to grow for a couple weeks before changing the soil pH. When I was ready to change the pH of the soil, I separated the plants into three separate bins, labeled with Acidic, Neutral, and Alkaline, three of each type of plant per bin. To make the soil alkaline, I created a mixture of lye and water, which changed the soil pH to 9.0, and to make the soil acidic, I gave the plants vinegar, changing the soil to a pH of 4.0. My control group I gave just water, the soil remaining at a pH of about 7. I gave each plant 40mL of the appropriate liquid 2-3 times a week. After 16 days of recording the height of each plant in centimeters, and making qualitative observations, I came to this conclusion: In acidic soils, the plants go quite floppy, and die after a couple days. In alkaline soils, the plants last slightly longer, but the leaves shriveled up quite a bit. My hypothesis was both correct and incorrect, as it only took a few days for all of the acidic plants to die while the alkaline plants died slowly over the course of a week.