You want to test the soil pH before you plant seeds or transplant seedlings into your garden. The pH can then be adjusted for plants requiring either an acidic, neutral or alkaline soil.
What Soil pH Means
Soil pH is an abbreviation for "Potentiometric Hydrogen ion concentration." This is a scientific measurement that reveals if your soil is acidic or alkaline.
- The soil pH range is 0-14.
- A pH 7 reading is considered neutral.
- A reading of pH below 7 means the soil is acidic.
- A pH reading above 7 reveals an alkaline soil with 10 being the highest level of alkaline.
Why Soil pH Is Vital to Plant Growth
The average pH level for most plants falls around 6.0 to 7.5. The pH reveals the availability of the nutrients that are essential to plant growth. Many crops are grown with the goal of a pH 6.5-7.0.
How to Test Soil pH Level With Litmus Strips
You can purchase a soil testing kit for around $10 for easy and fast determinations. The soil strips turn from a wide color range from red to black and give you an accurate reading of the pH range when compared to the accompanying chart.
- ½ cup of soil
- 1 litmus strip
- ½ cup of distilled water
- Place soil in a bowl.
- Add enough distilled water to create mud or a type of slurry.
- Remove one strip of testing paper.
- Dip strip into mixture.
- The paper will immediately turn.
- You may need to wipe off the muddy mixture with a piece of paper towel to see the color of the paper.
- Compare the test strip to the accompanying chart to see the pH reading.
- You need to test other areas of your garden since the soil in all areas of a garden are the same.
Test Soil pH With a Meter
You may prefer to purchase a 3-in-1 test meter or other type of meter specifically for soil pH. This type of meter measures the soil pH level, amount of sunlight and moisture in the soil. Simply follow the instruction on the meter; generally, you'll place in the soil at a certain depth and then read the results according to package instructions.
Baking Soda and Vinegar pH Test
If you don't want to wait on a kit, a very simple DIY soil pH test can determine if your garden soil is too acidic, too alkaline or neutral. You might not be able to get the right range of pH, but it will be sufficient for determining if you need the amend the soil. You can use baking soda and vinegar to determine if your soil is too acidic or too alkaline. Start with the baking soda instructions and move on to the vinegar portion if you do not yield results.
Collect Soil Sample
You'll need to collect one cup of garden soil. You want to sample the soil that is about 4"-5" below ground level. Once you have the sampling, you need to clean the soil, so it is free of leaves, sticks, roots, and any other material, including insects.
- 1 cup of garden soil
- Measuring spoon, tablespoon size
- ½ cup distilled water
- ½ cup distilled vinegar
- ½ cup baking soda
- 2 bowls
Baking Soda Instructions
- Place ½ cup of distilled water into one of the empty bowls.
- Place 2 or more tablespoons of soil into the bowl and mix until it is muddy.
- Add ½ cup of baking soda and stir to mix with the muddy mixture.
- If the baking soda reacts by foaming or fizzing, the soil is acidic.
- The pH level with this type of test typically ranges between 5-6.
Test With Vinegar if Baking Soda Is Inert
If there's no reaction to the baking soda, then you need to test a new batch of garden soil using vinegar. This will require using the second empty bowl.
- Measure 2 tablespoons of soil and place in the bowl.
- Add ½ cup of vinegar to soil.
- If the vinegar begins to bubble and fizz, the soil is alkaline. This usually means the pH level is between 7-8.
No Reaction to Baking Soda and Vinegar Tests
If there's no reaction to either the baking soda or vinegar test, you can assume your soil pH is 7 - neutral. You don't need to do anything to amend the soil.
High Acidic Soil pH Level
If the soil is too acidic, the plants won't be able to absorb needed nutrients, such as vital minerals. The plants will weaken, leaves will turn yellow and eventually disease and pests will overpower the plants. The plants may develop an iron deficiency and die if the pH level isn't corrected.
Remedy for High Acidic Soil
You can add amendments to the soil to neutralize the acidic soil with limestone. The University of Massachusetts Amherst recommends 70 pounds of limestone for every 1,000 sq ft of garden soil. The application should be mixed at a 4" depth.
Adjusting Limestone Amounts
The ballpark figure for adding limestone can be more or less when you take into account the type of soil, such as clay and those with a lot of organic material may require more limestone as well as calcium and magnesium. Other factors that may require more than one limestone application include how well the soil drains. For example, sandy soils usually require more than one application since the soil doesn't retain nutrients as well as clay soils.
High Alkaline Soil pH Level
If the pH test reveals alkaline soil, you can add amendments to lower it to a neutral pH 7. Iowa State University advises to use sphagnum peat, aluminum sulfate, elemental sulfur, acidifying nitrogen, iron sulfate, or organic mulches.
Remedy High Alkaline pH
The best way to lower alkaline levels is simply mix sphagnum peat into the garden soil. The university suggests for small home gardens to work a layer of 1"-2" of sphagnum peat into the first 8"-12" prior to planting.
Other Amendments Require Frequent Applications
If you wish to add other amendments, such sulfates and nitrogen you'll need to repeat these applications frequently. For this reason, many people opt for simply adding peat to their garden beds. You'll need more accurate and detailed testing before adding sulfates.
Choose Type of Test to Determine Soil pH
You can choose any of the available commercial tests or conduct a DIY test to determine the soil pH of your garden. A commercial test kit will provide a more accurate reading of your soil pH, so you amend the soil more precisely for better results.