Trees, shrubs, perennials and annuals are all affected by the pH of the soil. Our guide explains how to do a home soil test with an analyzer or with a cabbage.
Check the pH and nutrient content of the soil before planting trees, shrubs, perennials or annuals. Species that thrive in the soil’s natural pH are more likely to be well represented, especially trees. However, the pH can be adapted to a particular plant.
Some plants thrive in acidic soils with a pH of 6.9 or less, others prefer neutral soils with a pH close to 7 and others like alkaline soils with a pH of 7.1 or higher. If trees, shrubs, and plants grow in soils of incorrect pH, they may not be able to absorb the necessary nutrients, even if the nutrients are present in the soil. It is possible to adjust the pH to a particular plant, but you must first determine the natural pH of the soil. Soil test kits are available to home gardeners. They are usually sold in garden centers. An easier way that costs less, before you spend money on an analyzer kit, is to do a home soil test with a cabbage.
Do a home soil test with a cabbage if your plants are getting diseases
If the plants are already growing and have developed chlorosis or yellow foliage, the pH should be promptly checked and adjusted.
Check your pH for chlorosis.
Chlorosis can be caused by a variety of things, including too little or too much direct sunlight, herbicides, insect infestation and unusually extreme temperatures, but is most often caused by a lack of iron. Even if there is enough iron in the soil, which is usually the case, the plant can not absorb it if the pH is too high.
Chlorosis is indicated by bright green or yellow leaves. If the pH is not immediately adjusted, the foliage will die, branches will wither, and flowering plants may not bloom.
1. Do a home soil test with a cabbage
To determine if the soil is acidic, neutral or alkaline, a quick test can be performed before purchasing a soil pH test kit. WARNING: This only works with red cabbages.
- Take 1 tablespoon of soil out of the garden and let it dry.
- Bring 1 cup of distilled water in a pan with lid to a boil.
- Add 2 cups of chopped red cabbage to the boiling water, cover the pan and continue to boil until the water turns dark violet.
- Pour the purple water through a strainer into a bowl to remove the charcoal pieces.
- Allow water to cool.
- Put 2 tablespoons of the purple water with 1/8 teaspoon of baking powder in a white saucer.
- Stir the baking powder into the water until it changes color.
- Note the new color. It should be blue or green, indicating that the water is alkaline.
- Use a dropper to add clear vinegar to the water until the water changes color again. It should be red to indicate that the water is acidic.
- Put half a teaspoon of the dry earth in a clean white saucer.
- Use the pipette to add enough purple cabbage water to thoroughly moisten the soil. Tilt the saucer back and forth for a minute. Keep the saucer at an angle so that the water runs to the side of the floor and pay attention to the color of the water.
- Blue or green, the same color as the test pattern after adding baking soda, means that the soil is too alkaline for most plants.
- Red, the color of the specimen after adding vinegar, means that the soil is too acidic.
- If the color of the water drained from the ground is purple or purple-blue, it means that the pH of the soil is neutral to slightly acidic, which is ideal for most plants.
Dig to get your soil sample
The soil sample taken for testing with the when you do a home soil test with a cabbage or with a pH test kit should not be taken from the top as the roots of most plants are at least 2 to 4 inches below the surface. The pH above may be slightly different, so the sample should be taken where the roots of the plant absorb moisture and nutrients. Soil samples from areas where grass and annuals grow should be taken at a depth of 2 to 3 inches. Soil samples for shrubs, trees and perennial plants should be taken from a depth of 5 cm.
TIP: Wear gloves: Human hands can change the pH of the soil sample. Use a hand trowel or a shovel to dig up the top 2 to 4 inches of the floor. Collect 1 to 2 tablespoons of test soil, remove any pebbles or debris and place the soil in a clean bowl overnight to dry.
After drying, crush the sample by hand or with a spoonful until it is loosely and finely structured.
Take samples from different areas if the garden or yard is large. If the pH needs to be checked in various gardens in the garden, take a sample from each garden. The pH may be different in one part of the yard than in another. This is especially true for floors along a house foundation where lime tends to get out of the concrete into the ground and increase the pH.
- Place the soil sample in the test chamber contained in the test kit. Only fill it up to the bottom line indicated on the test chamber.
- Pour the test powder over the ground. Use a dropper to add distilled water to the test chamber. Only fill it up to the water fill line indicated on the test chamber.
- Put the cap on the test chamber. Make sure it is tightly closed.
- Shake the test chamber vigorously to thoroughly mix soil, powder and water. Stop the test chamber and wait one or two minutes for the floor to settle on the floor again and the watercolor change.
- Hold the pH chart included in the kit next to the test chamber to determine the soil pH.
- Perform the comparison in bright indirect light for the most accurate measurement. Direct sunlight can make the solution appear a little brighter.
- Collect nutrient content samples at the same depth as the pH. You should, however, collect 1 whole cup instead of a few tablespoons. Let the soil dry and shred. Pour the bottom into a large, clean container with a tight-fitting lid.
- Pour 5 cups of distilled water into the container with the soil.
- Shake vigorously for at least one minute or stir. Allow the soil-water mixture to stand undisturbed for up to 24 hours until the soil settles.
- Use a pipette to fill the test chambers and reference chambers in the container supplied with the kit with the test sample water.
- Only fill it up to the water filling line in the chamber.
- Use only the water without disturbing the bottom of the container.
- Put the test chemical in the water. There will be another chemical for nitrogen, phosphorus and potash. For example, the chemical used to test for nitrogen may be purple, the chemical for phosphorus may be blue and the chemical for potash may be orange.
- Close the test chamber firmly and shake it vigorously.
- Leave on for 10 minutes to allow the color to develop. Check it using the table in bright indirect sunlight to determine the nutrient content.
Carry out separate tests for nitrogen, phosphorus and potash
Wash and rinse the test chamber thoroughly between tests. If the test indicates that any of these nutrients are high or already at acceptable levels, use a fertilizer that does not contain this nutrient.
Choose your fertilizer
Fertilizers indicate the nutrient ratio as nitrogen-phosphorus-potassium or NPK. If the nitrogen content in the soil is acceptable, use a fertilizer with a ratio of 0-10-10 or something similar.
When plants receive excessive nitrogen, either too many stems and leaves grow or the roots can be burned.
If it is a flowering plant, it will plant lush new foliage, but may not flower. If the nitrogen content is low but the phosphorus and potash contents are acceptable or high, use fertilizers with a ratio of 10-0-0. Phosphorus helps plants to flower and potash helps them develop strong stems and improves their ability to absorb and use sunlight.
2. Do a home soil test: digital soil analyzer
Digital soil analyzers make it easier to test your soil. They are available in garden centers and online.
- Remove the top 5 cm of soil at the test site with a shovel.
- Using a shovel, loosen the next 5 inches of soil and remove any hard lumps of soil, rocks, sticks, or other debris.
- Pour distilled water over the ground until it is muddy and pack it by hand to remove any trapped air.
- Wear rubber gloves to keep the pH of the soil from changing with your skin.
- Polish the analysis probe with the supplied polishing cloth. Run the cloth from the tip to the meter and then wipe it with a cotton ball to remove dirt or debris.
- Do not buff or wipe the probe tip.
- Turn on the analyzer.
- Use the arrow key on the analyzer to select “pH” or “Fertility” depending on the test. Insert the probe 4 to 5 inches deep into the moist soil. If it does not slip in easily, pull it out and put it in another place.
- Do not force it into the ground as this could damage the probe.
- Turn the probe back and forth in the mud a few times to ensure good ground contact.
- Wait 60 seconds, pull the probe out of the ground and check the digital readout on the meter.
- If the reading is 7 or higher, wipe the bottom off the probe with a cotton ball and repeat the test. Insert the probe elsewhere in the mud and let it in for 30 seconds.
- If the initial reading is below 7, wipe the floor and repeat the test, leaving the probe to work for 60 seconds. The digital readout from the second test is the actual pH or fertility of the soil.