1. Label each cup with the name of the additive that will be used to treat the soil.
2. Fill each cup with one cup of soil from your garden. Test the pH of each sample and record the data. (The pH should be the same, but this just confirms that they are the same and that each sample is at the same starting point.)
3. Following the directions that come with the additive, add the correct amount needed to treat a cup of soil. Follow any other necessary conditions (time, watering) that are required of the additive.
4. After all of the soil samples have been treated, retest the pH of each soil. Record this data and compare.
Examining Your Results
You should now have a good idea of which additives will work and which additives will not work to treat your soil. To help narrow down your choices of which additive to use, you may want to consider the cost of the additive, how much work and preparation is needed to use it, and whether it is organic (natural). If you still haven’t picked just one additive to use, do a comparative study by adding one additive to one section of your garden, another additive to a different section, etc. See if the additives affect plant growth, either negatively or positively. You can also expand this by doing a longitudinal study. Keep your soil samples and retest the soil every month or so to see which additive keeps the soil at the right pH the longest.