How to: Get the right soil pH to grow the perfect vegetables!

‘Growing your own’ is an increasingly popular pastime. Many of us are shunning mass-produced produce in favour of something ‘more natural’. But what are the secrets of the perfect crop? Gardeners often hear people talk about soil pH, but most mere mortals haven’t got a clue what it means, how to test it, and what to do if it ‘isn’t right’. This excellent article from Heather Taddonio explains how to do it at home, and without any posh equipment…

So, growing season is well and truly upon us. If your garden plot isn’t starting to yield the bounty you planned, could the soil be to blame? You should test the pH of your soil to make sure it’s prepared for planting vegetables and fruit – but who seriously knows how to do that? What make a good soil for planting, anyway?

Understanding pH – in 30 seconds

reading pHThink back to 7th grade science class…remember learning about pH? I know, it’s probably a distant memory, so I’ll help you out. Potential Hydrogen (pH) is a measure of how acidic or basic/alkaline aqueous solutions are. It’s a logarithmic function of the hydrogen-ion concentration, which I won’t go into in further detail (you’re welcome). PH is measured on a scale of 1-14—a pH of 7.0 is considered neutral, while anything higher is alkaline and anything lower is acidic. In the classic science-textbook illustration of a pH test strip, milk and pure water sit at the center of the spectrum with a pH of 7.0. Battery acid has an acidity of about 1.5, while lye sits on opposite end of the strip with an alkalinity of about 13.5. Is it coming back to you now?

Your soil’s pH level determines nutrient availability for your plants as well as the absorption rates of those nutrients. In other words, taking the time to make sure your soil is in the correct pH range means happier plants and a hardier, more bountiful, and tastier harvest. Most fruits and vegetables grow best in more neutral soil with a pH of about 6.2-7.2, so if you’re within that range, you’re probably all set. Be sure to check the specifications for your particular plants, though, as some prefer soils outside of this range (blueberries, for example, thrive in more acidic soil with a lower pH). Check out the table that follows to find out the best pH for what you’re growing.

What changes a soil’s pH?

Soil is made up of crushed up parent rock, and the composition of this parent rock plays a role in determining the resultant soil’s pH. If the parent rock was a calcium carbonate-rich material, like limestone, the soil will likely be alkaline. Soils made up of silica-rich material tend to be more acidic. Rainfall helps leach basic (alkaline) materials like calcium from the soil, so areas prone to heavy rainfall tend to have more acidic soils. Rainwater itself tends to be a bit on the acid side, which is another contributing factor to acidic soils. If you live in an arid climate, it’s likely your soil is on the alkaline side since rain doesn’t have a chance to leach any of the basic materials out. All this goes someway to explain the regional differences in crops grown in different parts of the same country.

How to Test your Soil’s pH the easy way

The best pH for growing different vegetables
Table of ideal soil pH for different vegetables (click to open as pdf)

It’s suggested that you test your soil every 2-3 years for sandy soils or 3-4 years for clay-rich soils. But, if your garden is growing happily with no problems, you probably don’t need to worry too much. If you seem to have inexplicably lost your green thumb, it could be time for a pH test.

There’s a few options for measuring your soil’s pH. For the most accurate measurements and precise advice on how to amend your soil, send samples from your garden to a soil testing laboratory for analysis. They’ll send you back information on your soil’s pH level and advice on how much lime or sulfur should be used to properly amend your soil. A fancy store-bought at-home test kit or an even fancier electronic soil meter from your local garden store will yield less reliable results and no amendment advice, but will give you a good place to start.
Alternatively, you could do a quick-and-dirty (literally) at-home science experiment that will give you a rough estimate of your soil’s condition: Scoop a soil sample from your garden into a cup. Add some vinegar. If it fizzes, it’s alkaline (basic). If it doesn’t, scoop some fresh soil into another cup. This time, add a mixture of water and baking soda. If it fizzes, your soil’s acidic. If your soil doesn’t react in either case, the pH is already balanced and ready for planting and you’re all set. Adding soil amendments – how to change your soil pH

If you find your soil is too basic or too acidic, you may have to add soil amendments to get a healthy harvest. Adding lime to acidic soil or sulfur to alkaline soil will balance the pH, but it takes time for the amendments to be thoroughly mixed in, so be sure to test your soil about three months prior to planting.

Good luck!


Front slider image: Parisienne Carrots by Chiot’s Run, on Flickr

Article by Heather Taddonio

June 19, 2012

Heather trained at Bryn Mawr College, gaining a Majors in Geology. When not getting her fingers green, she works as a tour guide and social media expert.

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One thought on “How to: Get the right soil pH to grow the perfect vegetables!”

  1. Add sulphur to raise pH.

    Does that mean sulphur as in flowers of sulphur or as a sulphate?

    If a sulphate is that calcium sulphate or sodium sulphate or what?

    Or does everyone know (except me) what is meant by sulphate?



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