Just like humans, every plant has its specific nutritional preferences and needs. Some prefer sour soils, while some others want it sweet. The acid/sour vs. alkaline/sweet balance of the soil in your garden is measured using a pH scale. This pH scale indicates probable hydrogen ions that are available to help the plants process the soil nutrients. The soil balance determines which of the plants grow well in your garden. There are several natural soil amendments you can use to adjust that balance to shoulder a wider variety of plants.
How to Lower pH in Soil: 3 Easy Steps You Can Follow
Test It First
To determine the current pH of the soil, begin with a soil test. For soils that have a pH that is less than 7.5, you can add soil amendment (example: certain forms of sulfur) and effectively reduces the pH, once recommended. Any soil that has a pH above 7.5, adding an amendment to the soil may not minimize the pH that much due to the free marlstone or calcium carbonate present in the soils. This is one unfortunate characteristic of most soils in parts of Wisconsin. In such soils, you can grow plant species that are more tolerant of higher pH conditions.
Add Organic Matter
Most types of organic matter, such as compost, manure from compost, and acidic mulches like pine needles can reduce your soil pH very gradually with time.
As this organic matter decays, microbes feed and grow on it, thereby creating an acidic by-product along the line. Since organic matter requires time to decompose to change the soil, this is one great option for long-term goals, but won't produce dramatic results in the short-term. Most gardeners choose to incorporate organic matter into the soil annually, for gradual, moderate pH-reducing effect.
You can also get some more benefits from organic matter like improving its aeration and drainage.
Use Chemical Acidifier
You can also reduce the pH of the soil quite successfully by adding aluminum sulfate, elemental sulfur or sulfuric acid. What determines the material to use is how fast you want the pH to change and the size/type of plant that experiences the deficiency. Sulfuric acid, which is commonly used as battery acid acts very fast, but is quite dangerous, and it is not recommended to be used by home gardeners. However, green industry professionals, use sulfuric acid to minimize the pH of soil around vast, established trees for specimen. Homeowners can safely use elemental sulfur and aluminum sulfate. Aluminum sulfate acts faster than elemental sulfur due to its high solubility. However, elemental sulfur has the advantage of being more economical, especially if you are to treat a large area.
Generally, reducing the soil pH before you plant sensitive landscape ornamentals is the best practice, instead of trying to reduce the pH of the soil after the establishment of the soil. Make use of about 4-6 lb. of the aluminum sulfate for each plant for most of the medium- and finely-textured Wisconsin soils with the aim of reducing the pH of the soil by only one unit.
If you apply elemental sulfur, reduce the overall recommended application by 1/6. A pound of elemental sulfur or aluminum sulfate equals 2 cups.
For example, supposing you have an initial soil pH of 7.4, and you wish to plant blueberries that does not require a pH that is above 5.5. You will be required to apply between 8-12 lb. (16-24 cups) aluminum sulfate, or 1 1/3 - 2 lb. (2 3/4-4 cups) elemental sulfur for each plant. Give at least one month after application to prevent root burn.
If plants have been established already, make use of a top-dress application that is limited to 1 lb. (2 cups) of aluminum sulfate or 1/6 lb. (1/3 cup) elemental sulfur for every classical landscape plant. Incorporate the elemental sulfur or aluminum sulfate lightly into the soil, or water it in quite well. Repeat this application every month until the overall amount of elemental sulfur or aluminum sulfate has been incorporated. Since lowering the pH of the soil is a very slow process, check the pH of the soil 3 months after every application to ascertain if there will be need for more applications. There may be need for a lot of applications on the soil before any significant change can be noticed.
Making use of some specific fertilizers, like ammonium-containing nitrogen fertilizers such as ammonium sulfate or urea can help maintain the acid conditions, but such fertilizers will most likely not be very effective in soil pH experiencing significant reduction. The ammonium contained in such products in the soil to maintain the reduced pH. You must however, bear in mind that, a lot of fertilizer products like gypsum and potassium sulfate will not successfully reduce the pH of the soil.
3 Basic Rules on How to Lower pH in Soil
No matter the products you choose, you must adhere to the instructions contained in the pack thoroughly, even when you are required to purchase a special applicator or spreader before you can get it right. For instance, it is possible to grind a brand of sulfur more finely than another and applying too much of any product can destroy your plants. While the test results of your soil will make general guidelines available about the level of amendment required, go with the label on that particular product.
Apply the product and wait for like 3 months, test the pH of the soil again, and apply again if required. Getting your soil on track might take one or two years, and more harm than good can be caused by overdosing.
For maximum results, add pH-correcting amendments during fall, to allow them enough time to settle enough for spring planting. To most gardeners, soil testing and pH-adjustment are a yearly fall practice.