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How to Use a Soil Test Kit For Your Home Garden

We know that a lot of you have a garden or are planning on starting one in the future.

Last year we started a garden at our new house, but before we started planting we wanted to know what kind of soil we were working with. We decided to try using a soil test kit that you can do at home. It felt like a fun little science experiment and we wanted to share with other gardeners how we did it in case they wanted to try this home kit as well.

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What’s the Making of Healthy Soil?

Before we tell you how to use a soil test kit, we want to first tell you what an ideal garden soil will look like. Your soil should have a few important things:

  • Neutral pH level
  • Nitrogen
  • Phosphorus
  • Potassium (potash)

What are pH levels? 

The pH level of your soil ranges from acidic to alkaline. This range is measured in numbers from 1-14 and is referred to as the pH. Soil that is lower than 7 is considered acidic and anything above 7 is considered alkaline.

Depending on what you’re growing, you may want your soil to be more alkaline or more acidic. For instance, blueberries do well in acidic soil, lavender prefers alkaline soil. Most plants grow best in a neutral range of about 6.2 to 7.0.

Why are Nitrogen, Phosphorus, and Potassium Important?

  • Nitrogen may be the most important nutrient found in soil. It helps give plants their healthy green color and energy to grow and produce fruit.
  • Potassium is a nutrient that helps with photosynthesis and other physiological processes of plants.
  • Phosphorus helps plants grow roots, seeds, fruits, and flowers. Phosphorus also contributes to a plant’s ability to fight disease.

What You Need to Test Your Soil With a Soil Test Kit

You only need a few items to test your soil. Those items are:

  1. Soil Test Kit. We used a Rapitest soil tester that you can get at a local gardening store or online at Amazon. 
  2. Distilled water
  3. Soil from your garden
  4. Jar

How to Test Your Soil’s pH Level

We’re testing for four things, but the first thing to check is the pH level. Here’s how:

Step 1: Fill to the Soil Line in the pH Vial

The first step is to put a little sample of your soil in the vial. Fill until it reaches the “fill” line.

Step 2: Add the Powder

The next step is to open the green capsule and put the contents into the vial. It’ll look like this:

Step 3: Add Distilled Water

Using a medicine dropper (or we used a teaspoon measuring spoon) pour water until it reaches the fill line. Distilled water is best.

In this picture, Ned is using all of his power of focus. He will not spill a drop:

Step 4: Shake That Thing

Put the green lid back on the vial and shake it up. Shake shake shake. You can put on some Taylor Swift for motivation.

Step 5: Let the Soil Settle

The next step requires some minimal patience as you let the soil settle and reveal the color.

Step 6: Compare The Color of Your Soil Sample to the Soil Test Kit Chart

Compare the color of your soil. Ours revealed that our soil was neutral which is ideal for the largest variety of plants. Hooray!

How to Test Nitrogen, Phosphorus, and Potash

The next three nutrients in the soil are tested the same way, so I won’t share a separate section for each one. Here’s how to test:

Step 1: Mix the Soil With Water

Mix one part soil with five parts water. We mixed ours up in a little jar, but the directions say you can mix as much as one cup of soil with five cups of water.

Step 2: Shake it Up

Go ahead and bust out the Taylor Swift again because you’re about to shake up the dirt and water mixture. Shake until it’s somewhat combined and then allow it to settle. You’re interested in the murky dirt water that will appear on top.

Step 3: Add Your Dirt Mix

The next step is to get your vial and add the dirt mix solution. You’re only adding the watery portion of the mix. Don’t put the actual dirt in the vials. Add water to the appropriate fill line.

Step 4: Add the Appropriate Capsules

Add the appropriate capsules to each of the vials. The capsule will match the color of the lid. Once added, replace the lid and shake it all up again. Allow the vials to rest for 10 minutes. Don’t let it sit out longer or it may distort the results of the test.

Step 5: Compare Results With Soil Test Kit Chart

Here were the results of our test. Our potassium (potash) was in good order, if not a little high. The pH level was great. However, phosphorus and nitrogen were low which meant they needed to be added to our soil before we could produce healthy plants.

How to Balance Your pH Levels

If the results of the test show that your pH levels are too alkaline or too acidic to grow the plants you’re interested in growing, there are some things you can do.

For soil that is too alkaline, there are a few things you can do. It’s best to make these adjustments in the fall, but you can add things to your soil other times of the year.

  • Sulfur. You can add sulfur to your soil to lower pH levels, but the results will not be immediate. Try adding it in the fall after your last harvest and waiting until the spring to test your soil again. Sulfur lasts longer than some other options so you may want to try this one first.
  • Iron sulfate. This is a fast working solution but doesn’t last as long as sulfur. It can also be damaging to plants if overused.
  • Sphagnum peat moss. You can add this peat moss to your soil and till it in. The bonus of this option is it will also add organic material to your garden. You can also use it as a mulch around your plants if you’re able to work it a couple of inches into the soil.

If your soil is too acidic, you can try:

  • Limestone. This is by far the most common way to raise the pH level of your soil. Don’t use too much limestone as it can harm your plants. It’s best to add this in the fall and till in or work into the soil up to 8 inches. How much limestone you use will be determined by how acidic your soil is.
  • Wood ash. Wood ash can temporarily raise the pH level of your soil. This is fast-acting but will need to be repeated. Don’t use wood ashes from wood that has been chemically treated.

How to Increase Nitrogen in Your Garden

If your garden is low in nitrogen, there are a variety of things you can try.

  • Composted manure. Manure that has been composted can be a great way to raise the nitrogen level in your garden. We use chicken manure on ours with great results. Keep in mind that you’ll need to wait a period of time before adding chicken manure to your garden. If you go from henhouse to garden you run the risk of burning your plants because the nitrogen levels are too high before they’re properly composted.
  • Compost material. Regular composted fruits and vegetables can also add nitrogen back into your soil.
  • Add plants to your garden that add nitrogen. Some plants such as beans and peas will naturally add nitrogen to your soil.
  • Plant cover crops (also known as green manures). These plants are added to the garden not to be harvested but rather to provide rich nutrients back into the soil. You can plant these in the off season of your garden and they’re intended to be tilled back into the soil during the regular planting season. The added bonus is they also help keep the weeds out and reduces the risk of erosion. Examples of cover crops that raise nitrogen include:
    • Vetch
    • Beans
    • Peas
    • Clover
  • Use chemical fertilizers. Chemical fertilizers are fast-acting but their effects are short-lived. Many organic farmers argue that over time will actually harm your garden. They’re also not considered the most environmentally-friendly option.

How to Increase Phosphorus in Your Garden

Here’s how to increase phosphorus in your soil:

  • Bone meal. Bone meal is a fast-acting way to increase phosphorus when it’s added to your soil.
  • Organic compost. Your compost pile is a good source of phosphorus.
  • Manure compost.  Composted manure can raise phosphorus in the garden.
  • Chemical fertilizers. Chemical fertilizers can be used to raise phosphorus levels.

How to Increase Potassium in Your Garden

To increase potassium (potash) to your garden, you can add:

  • Muriate of potash or sulfate of potash. These are natural minerals that you can use on your garden. Sulfate of potash is a bit more pricey, but may be a better option since muriate of potash is sometimes known to harm soil microbes because of its chlorine content.
  • Wood ash. In addition to raising the pH level of your garden, wood ash can also raise potassium.
  • Kelp or seaweed. Kelp or seaweed can be a good way to raise potassium in the garden.
  • Compost. Your compost can help raise potassium in your soil. Composted banana peals can be a good boost for potassium.
  • Chemical fertilizers. Chemical fertilizers can be used to raise potassium levels.

What if Nutrients are too High in Your Soil?

You can also have the opposite problem with certain nutrients being too high. If that’s the case, there are a few things you can do.

When nitrogen is too high, you can stop fertilizing and add mulch to your soil. As the mulch breaks down it will absorb some of the nitrogen in your garden. Watering your garden regularly will also help decrease nitrogen in the soil.

To decrease phosphorus stop using fertilizers (such as composted materials). This is the main way to decrease phosphorus. If you need to add in other nutrients, such as nitrogen, try other methods that won’t increase phosphorus. For example, you can grow peas and beans to raise nitrogen without raising phosphorus.

When your soil has too much potassium, loosen the soil and water deeply. This can wash out some of the potassium from the garden. Removing rocks from the garden can also reduce potassium as minerals from certain rocks may cause the levels to rise. Avoid using fertilizers with potassium.

Are You Ready to Try Your Soil Test Kit?

This little DIY test kit is easy to use and actually pretty fun. Once you learn the results of your test you’re better equipped to plant a garden overflowing with fruits and vegetables. I’m really glad that we chose to take this extra step to learn more about our garden soil.

If you’re a new gardener or you’ve been gardening for awhile but having some problems, check out our guide Worst Gardening Mistakes and How to Avoid Them. In the guide, we include information on gardening soil and a WHOLE lot more.

As always, we love to hear from you. If you have any gardening advice or experience with a soil test kit, let us know in the comments below.










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