Testing Your Soil pH Levels

Soil pHYour soil’s pH is a term that’s thrown around a lot in the gardening world. For a beginner gardener, it can be a little intimidating as you have flashbacks of your chemistry class in high school. And unless you became a forensic scientist like my friend did, it was overwhelming! Luckily, this isn’t anywhere near as complex. This post will cover what your soil’s pH is and why it matters, vegetable pH needs, how to test soil pH levels, and how to adjust it if need be.

Soil pH & Why it Matters

Soil pH is a measure of the acidity and alkalinity in soil. pH levels range from 0 to 14. 7 is neutral. Below 7 is acidic. Above 7 is alkaline. At a more technical level that you don’t need to remember.. pH stands for potential of hydrogen. Acidic substances have a higher concentration of hydrogen ions. Alkaline substances have a higher concentration of hydroxide ions. Whew, OK, done with that now. 😉

The pH of the soil plays a significant role when it comes to growing because it affects nutrient availability for your plants. Nutrients could exist in your soil, but without the right pH level, your plants won’t be able to absorb them. For nutrients to be available they need to be soluble. And pH levels affect that solubility. So having the optimal pH for your plants will allow for optimal plant production – healthy, nutritional, and yummy!

Soil pH also affects soil-dwelling organisms, which in turn affect the soils conditions and plant health. Slightly acidic conditions are enjoyed by most plants, along with earthworms J

pH levels for plants should usually be between 6.0 and 7.0, but we’ll get more into that later. Soil pH is a result of multiple factors, including rain, fertilizers, and plants growing.

Rainfall contributes to a soil’s acidity. There’s some magic that happens and hydrogen ions replace calcium ions. So calcium is leeched from the soil and the soil becomes more acidic. This is why southeastern soils are typically more acidic than soil in the Midwest and west. Nitrogen Fertilizers contain or form ammonium. This increases soil acidity. The more nitrogen fertilization, the more the soil will become acidic. Legumes also release more hydrogen ions from their roots which cause the soil to be more acidic.

When pH levels are out of whack it can prevent plants from absorbing the nutrients they need, and also release other nutrients in such high levels that it basically poisons the plant. Yikes!

Vegetable Soil pH Needs

As mentioned earlier, pH levels for plants should usually be between 6.0 and 7.0. Some plants prefer more acidic soil, and others prefer more alkaline levels. Common exceptions include blueberries and potatoes that need more acidic soil to thrive. Below is a more detailed list for vegetables.

CroppH Soil
Beans6.0-6.8
Beets6.0-6.8
Broccoli6.0-6.5
Brussels Sprouts6.0-6.5
Cabbage6.0 - 7.5
Carrots5.5-7.0
Cauliflower5.5-7.5
Celery6.0-7.0
Chinese cabbage6.0-7.5
Collards6.0-6.5
Cucumbers5.5-7.5
Eggplant5.5-6.0
Endive/ Escarole6.0-6.8
Kale6.0-7.5
Kohlrabi6.0-7.5
Lettuce6.0-7.5
Melon6.0-6.5
Mustard6.0-7.5
Okra6.5-7.5
Onions, Bulbing6-6.5
Onions, Bunching6-6.5
Peas6.0-7.5
Peas, southern5.5-6.5
Peppers5.5-6.0
Potatoes, Irish4.5-6.0
Potatoes, sweet5.6-6.5
Radish6.0-7.0
Spinach6.0-7.5
Squash, Summer5.5-6.8
Squash, Winter5.5-6.8
Swiss Chard6.0-7.0
Tomatoes6.0-6.8
Turnips5.5-7.0

Testing Your Soil’s pH

Testing your soil’s pH is pretty easy with a pH meter. pH meters can vary in accuracy, but they give a good gauge. I use a Rapitest Soil pH Meter, but there are many out there that you can purchase. This one seems to get a lot of reviews on Amazon and is inexpensive: pH Meter. It’s basically a probe that you’ll stick into your soil. I usually do this in a few different spots to see what the average is. The meter will then hover over the pH level.

Adjust your Soil’s pH

Now that you know what your soil’s pH is, and what your vegetables need, you can adjust the pH of your soil as needed. If you need to adjust you’ll either raise or lower your soil’s pH level. Here are a few examples to do each.

Lowing your Soil pH

To lower the pH of your soil, or make your soil more acidic, you have a few options. Personally, I tend to use Blood Meal. You can also use sulfur or coffee grounds.

  • Blood meal is an organic nitrogen fertilizer that you can add to your garden. Adding blood meal to the garden soil will help raise the level of nitrogen and will help plants to grow more lush and green. The nitrogen will also lower your soil’s pH. Check out Painting your Garden Green with Blood Meal for Gardening to learn more.
  • Sulfur is also well known as a way to lower soil pH levels. You can find this in a powder form.
  • Coffee grounds are another way to lower soil pH levels. Keep in mind that only fresh, unused coffee grounds are acidic. Used coffee grounds are more neutral (about 6.5). But they’re still good to use as organic matter to improve drainage. Earthworms also like them 🙂

Raising your Soil pH

To raise the pH of your soil, or make your soil more alkaline, you have a few options. Here are a few that are natural and organic: bone meal, limestone, and eggshells. Personally, I tend to use Bone Meal.

  • Bone meal is a good source of calcium and can help raise your soil’s pH over time. It’s a slow release method and is best used for soils that are only slightly acidic. Check out Prevent Blossom End Rot with Bone Meal.
  • Limestone Adding pulverized limestone or dolomite limestone (which has magnesium & calcium) is one of the fastest ways to increase your soil’s pH.
  • Egg shells are also a source of calcium that can raise your soil’s pH over time. I’ve tried this method and haven’t had as much luck as bone meal, but I’ve read the best way for your soil to absorb it is if you crush it down to a powder, instead of just pieces like I have done. If you have a sledgehammer or maybe a coffee grinder you could try it out.

Keep in mind that once your soil reaches the pH level that is optimal, you’ll need to continually check it with your pH meter. As you continue to grow plants and there’s rain, your pH level will change. You’ll want to check about once a month to see if any more adjustments need to be made.

Do you check your soil’s pH? Comment below.

Happy gardening! 🙂

Soil pH

 

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