Some plants, such as camellias, lupins, garden lilies, and primrose, love acidic soils. If your soil isn't acidic enough or has been heavily treated with calcium oxide, here are some ways to slightly increase acidity and happily grow acid-loving plants.
Steps
Part 1 of 3: Testing the pH of Soil and Water
Step 1. For best and most accurate results, send a sample of your soil for professional testing
Of course, it's not very convenient to ask you to pay a lot of money for someone to give you a simple number. But if you're planning on growing plants or making the soil more acidic for whatever reason, you have to agree that professional sampling is more accurate than home DIY testing. It might even seem like a similar value to you, but the difference between a 5.5 and 6.5 soil on the pH scale is quite large!
Step 2. Try a pH test with a home DIY
If you don't like the idea of professional soil testing, you can easily test your soil pH at home, but you need to understand that your measurement will not be as accurate as a professional assessment. There are several ways to get a pretty decent reading at home:
- Use the paper strips to test the pH. This method will only tell you if your soil is mostly acidic or basic, but it is a fun exercise that can be used with many different flowers, vegetables and herbs.
- Use vinegar and baking soda to test the pH. Another rudimentary way of testing involves adding vinegar and baking soda to the soil separately to see if it produces frothy bubbles. If it reacts with vinegar, it is basic or alkaline; if it reacts to sodium bicarbonate, it is acidic.
- Buy a kit for a home test - it should be able to detect the pH of your soil giving you a more significant number than any other do-it-yourself method.
Step 3. Make sure you also test the pH of the water
The pH of the groundwater that can be used to water your plants varies from about 6.5 to 8.5, but it tends to be more alkaline so as not to corrode the water pipes. If the water you use to water your plants is basic, like soil, know that you will need a small addition to produce the desired acid effect for your plants.
One way around this potential problem is to use pure, filtered water. It has a pH of 7, which makes it almost completely neutral. Using pure, filtered water is effective, but it can get expensive in no time
Step 4. Learn how to read the pH of any test used
PH is a measure of how basic or acid a substance is. This measurement is taken on a scale of 0 to 14, with 0 very acidic (think battery acid) and 14 very alkaline (for example, the liquid that cleans drains). 7 is considered "neutral" on the pH scale.
For example, if your soil is 8.5 on the pH scale, it means it's a bit basic. Some siliceous material will need to be added to make the soil less alkaline. If your soil measures 6.5 on the pH scale, it means it's a bit acidic. If you want your soil to become even more acidic, you need to add more siliceous material
Part 2 of 3: Soil Acidification
Step 1. Identify the type of terrain
This is different from determining its pH and is a really important tactic. Soil type will tell you which acidifier method you should use.
- Soil that is already relatively loose and well drained will make acidification much easier. This type of soil can benefit from large amounts of organic compounds that acidify the newly poured soil.
- Soil that is mixed with clay and very compacted will make acidification much harder. Adding organic material to this type of soil will make it more alkaline, not less.
Step 2. Add organic materials for loose, well-drained soils
To acidify these types of soils, organic materials are the best solution. They acidify the soil as soon as they are distributed, but large quantities are needed to lower the pH. Here are some good organic materials that we recommend you use:
- Sphagnum peat moss
- Compost from oak leaves
- Compost and manure
Step 3. Add some elemental sulfur to the soil that is heavily compacted or has a lot of clay
As mentioned earlier, adding organic materials to very dense soil can make problems worse, because the soil retains more moisture, making it more alkaline. For this reason, adding elemental sulfur or iron sulfate is the safest way to acidify the soil with heavy clay components.
- Elemental sulfur acidifies the soil, as bacteria transform it into sulfuric acid. It takes about 1 kg of elemental sulfur every 10 square meters to be able to reduce the pH of a soil from 7 to 4.5.
- As elemental sulfur is slow to react, it is best to add it the year before implantation for best results.
- Work the elemental sulfur into the soil, going 15 centimeters deep.
Step 4. Add iron sulfate to heavily compacted or clayey soil
Iron sulfate relies on a chemical reaction to create acidity. It is therefore less dependent on temperature conditions than elemental sulfur, which depends on bacteria to produce a biological reaction.
- It may take more than 5 pounds of iron sulfate for every 80 square meters of land to reduce the pH by one unit.
- Iron sulfates react much faster than elemental sulfides. They can significantly reduce the pH in 2-3 weeks instead of several months. This gives them the advantage of being usable in the same season as you decide to plant.
- Be careful when applying iron sulfates. They can cause rusty stains on clothing, sidewalks, and patios. It is best to separate iron sulfate stained clothes from other clothes - wash them separately to avoid any contamination.
Step 5. Use a fertilizer containing ammonia
In many cases, all that needs to be done to acidify the soil is to use an ammonia-based fertilizer. Many of the fertilizers used for acid-loving plants contain ammonia sulfate or sulfur-coated urea.
Calcium and potassium nitrate should not be used as fertilizers, even if they contain ammonia. These fertilizers actually raise the pH of your soil
Part 3 of 3: Maintain a Suitable pH for your Plants
Step 1. If the flowers or plants have just been planted, use some elemental sulfur
Being slowly absorbed, it is difficult to make mistakes with the recommended doses. Work it in moist soil as much as possible, without interfering with any root structures. Continue to monitor the soil pH as the months pass.
Step 2. Resist the urge to add vinegar to your soil
Vinegar will lower the pH of the soil immediately, but, in this case, it wouldn't be much good. The change happens too radically, disappears too quickly and kills the beneficial organisms of the soil. Stay away from vinegar, unless you want to accept the possibility that your plants may die.
Step 3. Use cottonseed meal as an acidifying fertilizer throughout the year
So, if you've already treated your soil with iron sulfates, for example, and just planted your blueberries, keep the soil pH low by applying a generous amount of natural acidifying fertilizers like cottonseed meal. This byproduct of cotton production is particularly effective for acid-loving plants such as azaleas, camellias and rhododendrons.
Step 4. Monitor your pH closely at least annually
Check the pH of your soil near the base of the plants by adding fertilizers such as aluminum sulfate (especially for hydrangeas) without damaging the root system. For best results, use a pH test kit or send a sample of your soil for professional testing.
- Ornamental plants and vegetables mainly prefer a slightly acidic environment between 6, 5 and 6, 8.
- Hydrangeas, azaleas, rhododendrons and blueberries prefer a more acidic environment, between 5 and 5, 5.
Step 5. Increase the pH of your soil, if necessary, with lime
In some cases, your efforts to acidify the soil will work so well that you will get too acidic soil for your plant. In these cases, you will want to alkalize your soil by adding lime, which comes in three basic varieties - limestone, hydrated lime or calcium oxide. The amount will depend on the type of soil available, as well as the variety of lime you choose to use. Look for the instructions on the package or talk to a horticulturist for more information.
Advice
- Sulfur flowers are a very fine powder of pure sulfur. You can find them in garden centers or order them online.
- Iron salts could also be beneficial; soils that are too alkaline can "block" the iron, preventing it from reaching the plants that need it. Check how the first treatment goes before adding more.
