Aluminum sulphate is used to lower the pH level of soil. Most plants typically thrive in a soil that has a pH between 6 and 7, which is slightly alkaline. However, some plants yield larger flowers or fruits when the soil is more acidic. You can safely use aluminum sulphate to lower the pH of your soil to increase yield of blueberries and strawberries, to create bigger blooms on your azaleas and rhododendrons, and to change the color of hydrangeas.
Things You'll Need
- Soil pH test kit
- Work gloves
- Garden rake
- Aluminum sulphate
- Garden hose
Test the pH of your soil with the test kit and read the results.
Determine the amount of aluminum sulphate you need to put your soil. For every one full point of pH that you need to lower, you will have to add between 1 and 1.5 pound of aluminum sulphate. For instance, if your soil pH is 7 and you want to lower it to a pH of 5, you will have to add approximately 2 1/2 pounds of aluminum sulphate.
Rake up the top 6 inches of soil. Evenly spread aluminum sulphate and cover it with the soil. Water the soil thoroughly to ensure that the aluminum sulphate dissolves and enters the soil.
Tips & Warnings
- It is better to use too little aluminum sulphate than to use too much, because it can burn the plant roots and kill them.
- Take care not to get the aluminum sulphate on the leaves or stem of plants or it will burn them.
- Do not use aluminum sulphate in the soil near ponds or lakes that have fish or aquatic life, because it can poison them.
- Wear work gloves when handling aluminum sulphate. Wash hands immediately after use.
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