The best gardens have the best soil for the plants growing in them; soil is the foundation for a thriving garden. It's also where your plants will get the majority of their nutrients, housing the young seedling and providing the starting point for growth. Make sure that your soil is up to the task before you start gardening by checking your soil’s health.
Should You Test Your Soil?
Good soil can be the difference between your lush, productive garden and your neighbor’s sad and wilty one.
It’s a good practice to routinely test your soil. Growing plants will take up nutrients from the soil and unless you’re replacing them, the soil won’t just generate these nutrients on their own. You’ll need to monitor the soil’s health and add fertilizers or amendments as the soil is depleted.
Avoid nutrient deficiencies by amending the soil regularly. For vegetable gardens, test the soil at the end of a growing season. This will give you time to amend the soil and add nutrients back before you replant.
You can also test bagged soil that you plan on filling containers with. Most bagged soil is healthy, but it’s always reassuring to double check.
If you’re making major amendments, test the soil again before you plant to prevent burning the roots of your plants.
What are You Testing For?
There are several things that you can test your soil for. The most common nutrients that you’ll test for include the primary macronutrients: nitrogen, phosphorus and potassium. Without these nutrients, most plants won’t survive long.
If you want a complete analysis of your soil, you’ll have to have your soil professionally tested. This can be costly and usually isn’t necessary to grow gorgeous flowerbeds or productive vegetable gardens.
You can also test the soil’s pH level. The pH level tells you how acidic or basic the soil is. The pH is rated on a scale from 1-12. 7 is considered neutral. Anything below 7 (0-6.99) is considered acidic. Anything above 7 (7.01-12) is considered basic or alkaline. Most vegetable plants grow best at a slightly acidic soil. Most flowering and landscape plants grow best in soil that is between slightly acidic-neutral.
The pH is important because it determines how available the nutrients are in your soil. If the pH isn’t right, your plants won’t be able to absorb nutrients, even if the nutrient levels are high.
If you’re using a digital soil analyzer, you’ll be able to test the soil’s temperature also. This isn’t necessary, but it’s a good feature to know if you’re planting seeds in the ground.
Seeds can’t germinate if the soil isn’t warm enough. The temperature needed for seed germination will vary depending on the type of plant.
Using a Soil Test Kit
A soil test kit is one of the easiest ways to get an idea of your soil’s health.
You may think that the darker your soil is, the healthier it is. While this is a good general rule, it’s not always true. Looks can definitely be deceiving! Test your soil to get a true analysis of your soil.
I’m going to walk you through how to use a soil test kit. It may seem complicated, but it’s really not! It’s pretty simple and won’t take long at all.
All soil test kits are slightly different but they test for the same things. I’m going to walk you through using a professional soil test kit by Environmental Concepts. In order to test your soil, you’ll need a soil sample.
It’s a good idea to take several soil samples since the soil can vary greatly from one location to another. If you’re testing the soil for vegetable gardens, take the sample from about 4” deep. The same is true for perennials that will develop deeper root systems. For lawns, annuals and houseplants, take the soil sample from 2-3” below the surface since these plants tend to have shallower roots.
Don’t touch the soil with your hands.
Put the soil into a clean container where it can dry out. The drier your soil sample is, the easier it is to test. When your soil sample is dry, remove any small rocks, sticks, mulch, pieces of grass or other organic material. Crumble the soil up into a fine consistency and mix it up.
Testing for pH
Get out one of the clean test tubes. You’ll notice that it’s marked in milliliters. Using the small scoop in the test kit, fill the test tube up to 1 mL with your soil. Wipe the scoop clean.
Add one scoop of barium sulfate to the soil sample. The barium sulfate will help the sample to settle so that you can look at your pH results. Wipe the scoop clean again.
Next, get out the bottle labeled ‘pH Test Solution’. Slowly start adding the solution to the test tube with the soil sample and barium sulfate. Fill the tube with pH solution up to the 2.5 mL mark.
Put the top on the test tube. Shake the test tube vigorously for about 30 seconds. Set the test tube to the side and allow it to settle for 5 minutes.
After five minutes, the soil should be settled enough for you to read the results. Compare the liquid above the soil to the chart included with the test kit. If the soil hasn’t settled into a different layer at the bottom of the tube, add another scoop of barium sulfate, shake it up again and wait another five minutes.
Testing for Nitrogen(N), Phosphorus(P) and Potassium(K)
Before you can test for N, P and K, you’ll need to get the filtering device ready.
Start by removing the green cap on the filtering device. Take the plunger out. You’ll see one end of the plunger has several small holes in it. Get out one of the filter papers and place it into the end of the plunger.
Use the scoop to press the paper down tightly into the end of the plunger. Now you can fill the barrel of the test tube with your soil.
To test all three nutrients, you’ll need to prepare a sample in the filtering device for each nutrient you want to test.
For nitrogen, fill the barrel up to the 1 mL mark with soil. Then, get out the bottle labeled N1 Nitrate Extractant Solution. Fill the barrel up to the 2.5 mL mark. Place the plunger back into the filtering device just enough to keep it in. Shake the filtering device gently for 30 seconds. Press the plunger down gently until the tip of the plunger just touches the soil solution in the barrel.
Screw the cap back onto the filtering device. Screw it down slowly. This will cause the plunger to press down into the solution. Continue screwing the cap down until there is adequate solution in the plunger. Don’t tilt the filtering device. The cap has a hole in it and you’ll spill the solution if you’re not careful.
Remove the cap and pour the solution from the plunger into a clean test tube. If you’ve done it properly, you should have a test tube with solution that is free of debris or soil.
Fill the test tube to the 1mL mark. Add one scoop of the N2 Nitrate Reactant Powder to the test tube. Place the cap on it and shake it for 10 seconds. Let the test tube sit upright for 5 minutes.
Compare the solution’s color to the chart included in the test kit. To test for phosphorus and potassium, clean out the filtering device and test tubes with soap and water. This will prevent contamination between tests that could affect your results. Place a new filtering disc in the filtering device.
For phosphorus, fill the barrel of the filtering device with .5 mL of soil. Then add the P1 Phosphorus Extractant Solution to the barrel until it reaches the 2 mL mark. Shake it for 30 seconds and then filter out 1 mL of solution using the same methods that you used for the nitrogen test.
Once your test tube has 1 mL of solution in it, add ½ of a scoop of the P2 Phosphorus Reactant Powder. Place a cap on the test tube and shake it gently for 5 minutes. Immediately remove the cap and compare the color of the solution to the chart included in the test kit. Clean the filtering device and test tubes with soap and water before testing for potassium.
For potassium, fill the barrel of the filtering device with .5 mL of soil. Then add the K1 Potassium Extractant Solution to the barrel up to the 2 mL mark. Shake it for 20 seconds and then filter out 1 mL of solution using the same methods that you used for the nitrogen and phosphorus tests.
Once your test tube has 1 mL of solution in it, add 0.5 mL of the K2 Potassium Reactant Solution. Don’t shake it up. Let the solution stand for 5 minutes. You’ll notice that the solution is cloudy. The degree of cloudiness indicates how much potassium is present. Place the test tube in the circle next to the potassium reading chart. Place it on the surplus reading first and move it down the chart until one of the boxes is just visible. That is the reading for your sample.