Vegetable gardeners spend a lot of time thinking about conditions that affect the successful growth of plants, such as rainfall, sun, and temperature. But they often neglect the soil, which is where plants get the nutrients they need to grow. The pH of the soil determines the availability of these nutrients; so, for plants to flourish, you need soil with the right pH value for the plants you’re growing.
Fortunately, you can change the pH value of your soil, naturally, for healthy plants and a productive garden.
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What Are Soil pH Values?
By nature, soils can be acidic or alkaline. You can determine what type of soil you have by measuring its pH value. There are several ways to test soil pH. For instance, you can take a soil sample and send it to a lab for analysis, use a store-bought test kit, or create a DIY soil pH test.
It should be emphasized that the results obtained from a DIY test will not be as precise as a laboratory test, but they will certainly give you some clues as to whether your soil is acidic or alkaline. Learn more about soil pH testing methods.
Providing soil with the correct pH value is the best thing you can do for your plants.
Most soils have a pH value somewhere between 3.5 and 10. In regions that have a lot of precipitation, soil pH values usually range from 5 to 7, while in drier regions, pH values usually range from 6.5 to 9.
Here is a quick reference for classifying your soil according to pH value:
- 7.6 and above: alkaline
- 6.5 to 7.5: neutral
- 6.5 and below: acidic
- Less than 5.5: strongly acidic
According to experts from the University of Nebraska – Lincoln, most vegetables do best in a pH or acidity in the neutral range of 6.5 to 7.
However, some plants grow much better in soil that is slightly acidic, in the range of 6.1 to 6.5. Why is that so? Such plants need higher levels of certain nutrients whose absorption is improved by the presence of more acids in the soil. This group includes carrots, cauliflower, celery, cucumbers, garlic, sweet peppers, pumpkins, squash, and tomatoes.
Furthermore, some plants perform more optimally at a pH closer to neutral. These plants include sweet peas, kale, lettuce, green beans, cabbages, brussels sprouts, broccoli, asparagus, and radishes. On the other hand, potatoes do best in soil that is significantly more acidic, up to a maximum of 6.0.
How To Change the Soil’s pH Naturally
Adding organic matter is one of the best methods for improving the conditions for growing vegetables, or in this particular case, adjusting the pH value of the soil.
Natural amendments are usually added to improve soil structure, as well as to increase organic content and improve moisture retention. Keep in mind that the richer the soil in amendments, the healthier the plant’s roots are. In healthy soil with appropriate natural supplements, adjusting the pH level won’t be as necessary as plants develop their tolerance to acidic or alkaline conditions.
Raising the pH for More Alkaline Soil
1. Limestone
Adding limestone is one of the most common ways to raise the pH of your soil. Because adding limestone is not a quick solution, it is best to do it in the fall, at the end of the growing season, long before sowing or transplanting seedlings.
Ideally, you’d use a fertilizer spreader to distribute the limestone evenly. But if you don’t have one, you can use a shovel to spread the lime evenly over the top of the soil. Once you’ve spread it out, dig up the soil to incorporate the lime as deep as the root system of your plants will grow. Then water thoroughly. The amount of limestone you use depends on your soil’s needs, but below are some rough numbers.
- Sandy soil needs about 2 pounds of limestone per 100 square feet.
- Loamy soil needs about 3.5 pounds of limestone per 100 square feet.
- Clay soil needs about 5 pounds of limestone per 100 square feet.
Learn more about limestone application.
2. Wood Ashes
Using wood ash is one of the easiest ways to naturally change soil pH but it is not long-lasting. All you have to do is spread roughly ¼ inch of wood ash evenly over the surface of the soil to be treated, preferably on wet soil so that the wind doesn’t blow it away. Then use a rototiller, spade, or rake to work it into the soil. Avoid using chemically treated wood ash at all costs to avoid contaminating your soil.
3. Baking Soda
Using baking soda is a cost-effective, quick, and easy method of increasing the pH of your soil. All you need to do is mix a tablespoon of baking soda into a gallon of water and water your plants thoroughly. You will get the best results if you repeat the procedure every few months.
Lowering the pH for More Acidic Soil
1. Elemental Sulfur
Did you know that soil bacteria change sulfur into sulfuric acid, which lowers soil pH? It is very important to emphasize that sulfur can even increase the resistance of plants to diseases.
For best results, apply sulfur before planting and then till to a depth of 6 inches. This helps speed up pH adjustment. However, if you are applying it to soil where you already have planted, you will need to add elemental sulfur little by little whenever possible. Gently rake to mix it into the soil without disturbing the plantings.
For example, if you want to plant blueberries that need a pH of up to 5.5 but your soil pH is 7.4, feel free to use about 1 1/3 to 2 lbs. (2 3/4 to 4 cups) elemental sulfur per plant. To avoid burning the plant’s roots, it is essential to do this before planting your blueberries.
If the plant is already established, use 1/6 lb. (1/3 cup) of elemental sulfur per plant. Repeat the process for the next month until your soil reaches the desired pH level.
2. Peat Moss
Peat moss is an excellent soil amendment for acid-loving plants and can also help retain moisture in the soil. Note that the action is quite slow and there is a chance that it will not be effective in causing significant soil pH changes. If you go this route, we recommend adding a 1-inch to 2-inch layer of peat moss and incorporating it into the top 6 to 12 inches of soil before planting. Unfortunately, the harvesting of peat moss destroys environmentally beneficial wetlands and releases CO2, a major contributor to climate change. So, we recommend alternate solutions for lowering the soil’s pH.
3. Vinegar
To lower the soil pH with vinegar, you need to create a diluted vinegar solution. Mix 1 cup of vinegar for every 1 gallon of water and water your plants using a watering can or inject it into your irrigation system. This is quite enough to start with, test the soil regularly and in case you don’t see any changes or the changes are very small, feel free to use one of the methods mentioned earlier.
Gardening Starts With the Soil
It is well known that success in gardening starts with the soil; it is the foundation of your entire garden. Accordingly, the appropriate pH value is of great importance as it determines the availability of almost all essential plant nutrients.
You can’t have healthy, productive plants without quality and balanced soil. This is where natural amendments, which have the ability to improve overall soil condition as well as deliver nutrients directly to your plants, come to the rescue.
Finally, don’t get discouraged if everything doesn’t work out the first time. While it may take some time to determine exactly which actions will produce the best results, it is possible to make the most of the garden soil you have.
This article was originally published on September 13, 2022.
About the Author
Tony Manhart is the founder and editor-in-chief at Gardening Dream. Tony’s enthusiasm and rich experience in all things related to growing plants have led him to share his knowledge with gardening aficionados all over the world. When he is not working around his garden, Tony spends his time writing tips and tricks on various subjects related to plant cultivation and soil maintenance.