tomato care tips
Organic Gardening

7 Facts About Soil pH for Tomatoes and How to Raise and Lower It

best soil pH for tomatoes

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Tomatoes are one of my favorite crops to grow and the one I’ve grown the longest. They’re an easy crop to start out with and a garden favorite to many. Soil pH is important not only for tomato plants to thrive, but it affects the taste as well. Tomatoes are an acidic loving plant. To learn more about tomato care tips, read on!

This post is all about soil pH for tomatoes.

[RELATED POST: How Long Does It Take to Grow Tomatoes From Seed?]

Review of Soil pH

Before diving into soil pH for tomatoes, let’s review the basics about soil pH. pH stands for ‘potential hydrogen’ and is an indication of soil reactivity. It indicates whether something (in this case soil) is alkaline, neutral, or acidic. The pH scale ranges from 0 to 14, with 7 being a neutral point. As the amount of hydrogen ions increases, the soil becomes alkaline. When the hydrogen ions decrease, soil becomes more acidic. pH affects nutrients, minerals, and the growth of plants.

The most accurate way to measure soil pH is with a pH meter. Another way to measure it is by using certain indicators or dyes. This second method isn’t as accurate.

Best Soil pH for Tomatoes

The ideal soil pH for tomatoes ranges between 6.0 to 6.8. Although tomatoes love acidic soil, they don’t like soil that’s too acidic. As mentioned previously, pH affects nutrients, minerals, and the growth of plants. At a pH level between 6 and 7, nutrients are the most readily available. As the pH levels vary in soil, so too does the availability of certain nutrients. For example phosphorus is never readily soluble but is available to plants when the soil acidity reads pH 6.5. When nutrients aren’t soluble because of the pH, they can’t be used by plants.

Can soil be too acidic for tomatoes

The best soil pH for tomatoes ranges between 6.0 to 6.8, but they can still do well down to a pH of 5.5. Having the soil too low though inhibits the absorption of calcium, magnesium, nitrogen, phosphorus, potassium, sulfur, and other nutrients as they become less available. The inability to absorb the nutrients the plant needs leads to all kinds of health issues like stunted growth, reduced or no fruit production, and different diseases.

How to Test Your Garden Soil

There are a couple of ways to test your garden soil. The most accurate way to measure soil pH is with a pH meter. Another way to measure it is by using certain indicators or dyes. Soil tests are readily available at garden centers. However I think it’s always best to get a full comprehensive report of the soil in the garden. There are plenty of testing kits on the market that you can get through websites like Amazon, or check out your local university’s cooperative extension.

It’s good practice to test your soil before proceeding with any amendments. A comprehensive test will tell you exactly what your soil has and what it’s lacking so you can make the appropriate adjustments.

test soil

How to Increase Soil pH, or Lower Acidity

Now that we have a basic understanding of what pH levels are, what the best soil pH for tomatoes is, and how to test your garden soil, we can now talk about adjusting soil acidity.

How to Raise pH in Soil Naturally

Here are a few recommendations as to how to raise pH in soil naturally:

  1. Compost is a great resource in the garden. The nutrients it contains lack acidity and thus won’t increase the soil pH.
  2. Wood ash has so many different nutrients for the soil. It’s composed of up to 20%+ calcium, potassium (or potash), magnesium, phosphorus, and sulfur. There are also trace amounts of boron, iron, aluminum, manganese, zinc, and more. 

*** Be careful using wood ash. If you use Duraflames, don’t use the wood ash from your fireplace. Duraflame logs are prefabricated and contain lots of chemicals.

  1. Garden lime is one of my favorite additions to use for soil amendments. It’s something I’ve used since I began gardening and it’s an easy application. I buy a bag of the pulverized garden lime, which is a very fine, white powder.
  2. Bone Meal is a fertilizer that’s made from steamed animal bones. It’s not the best smelling product but it’s an organic way to help the soil pH. It adds calcium into the soil and over time raises the pH.

How to Lower Soil pH for Tomatoes, or Make it More Acidic

  1. Add lime (aka limestone).  It’s one of the most commonly used materials to help raise pH levels naturally. It can be found in many garden centers, including big box stores. I’ve had a lot of success by adding in lime and this is usually what I use to make it more acidic.
  2. Sulfur: This amendment needs to be added well in advance since it takes a long time to lower the pH of the soil. Apply sulfur the year before you plant.
  3. Iron sulfate requires a large volume to lower the soil pH. Check your soil analysis before you start adding in iron. Iron sulfate is used to treat iron deficiencies too, and provides quicker results in comparison to sulfur.
  4. Sphagnum Peat Moss: this amendment requires a large amount added to the soil as well. Adding it to the soil only slightly affects the acidity, but it adds more organic material. Add in the peat moss will help lower the soil pH for 2 years.
  5. Acid fertilizer: there are many acid fertilizers on the market. Try fertilizers like: Burpee Organic Tomato & Vegetable Granular Plant Food. This Burpee product is organic and it releases over a 3 month period.
  6. ****Aluminum sulfate is another amendment that is popular. There are recent concerns about the use of aluminum in the garden. Not only can it be hazardous to our health, but it contaminates drinking water and groundwater. I’ve included this in the list since it can help with soil, but including this warning to steer clear of it.
  7. Ammonium sulfate is used around the base of plants to increase the amount of sulfur in the soil. Pay close attention to how much is used since ammonium can burn plants.
  8. Compost is always a great option in the garden. Check out my other posts on compost to help you choose the right one.

[RELATED POST: All About Mushroom Compost for the Vegetable Garden]


•Tomatoes are an acidic loving plant, and the ideal soil pH for them is between 6.0 to 6.8.

• The most accurate way to measure soil pH is with a pH meter.

• Low acidity can the absorption of nutrients by plants. Malabsorption leads to stunted growth, reduced or no fruit production, and an increased chance of disease.

• To raise the soil’s pH naturally, add compost, wood ash, garden lime, or bone meal.

• Lowering the acidity involves adding lime (limestone), sulfur, iron sulfate sphagnum peat moss or an organic fertilizer like Burpee Tomato & Vegetable Granular Plant Food. Aluminum sulfate can be used but should be avoided due caution of health concerns.

This post was all about soil pH for tomatoes.

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