Soil PH @ 7 - how do I get soil at better ph level for vege garden #744426 - Ask Extension


Soil PH @ 7 - how do I get soil at better ph level for vege garden #744426

Asked April 15, 2021, 9:12 AM EDT

This is a phone call that came into the helpline. Hello: I have a digital soil reader that indicates my soil ph is @ 7. How do I get a better ph level for my vege garden? Will compost/manure help or make it worse?

Chittenden County Vermont

Expert Response

Hi Lacy! Good for you for knowing how important soil pH is for your plants!

First:  the accuracy of digital pH meters varies.  You can get a professional soil test through our extension office for $15 -- instructions and the order form can be found on our web site. There's a link at the end of this response.  In addition to pH, the soil test results also tell you about macronutrients (phosphorus, potassium & magnesium) and the organic matter percentage of your soil.

Without that additional information and any knowledge of the plants you wish to grow, I think the best I can do is to offer you our UVM Extension "pH for the garden" fact sheet:

As noted in the document: plants have different pH ranges.  They are best able to take up nutrients and thrive in the middle of their ideal pH zone.  (So a plant that likes a pH of 6 to 7 will usually get by if your soil's pH is 7...but it will do better with soil pH closer to 6.5.   Depending upon what you want to grow in your garden: you usually try to keep your soil pH in a good range for most of the plants.  Often, we find that a pH range of 6 to 7 works pretty well for most vegetables and flowers. But look at the chart at the end of the article to see the target range for different plants.  Note that some plants need more acidic soil:  blueberries, azaleas & rhododendrons & conifers are in this category.  Also:  if you don't see a plant listed that you plan to grow: you can Google "pH of xxxx."  Don't be surprised if you see a little bit of variation from different sources.

So if your soil is at a pH of 7.0 and the plants you want to grow would be happier with a lower pH:  you can work elemental sulfur into the soil.  The fact sheet lists amounts (e.g.:  to go from 7.0 to 6.5:  1 lb of elemental sulfur per 100 square feet of garden) - but do heed the warnings about maximum applications (both amounts and timing) -- too much can burn plant roots. 

Also:  pH is on a logarithmic scale.  A pH of 6.0 is TEN times more acidic than a pH of 7.0.  (And a pH of 8.0 is ten times more alkaline than 7.0)  This is why it takes some time to shift the pH in soil and why it can make such a big difference.

Finally:  without knowing the organic matter percentage of your soil, I can't really advise you about adding compost and/or manure. Usually an annual addition of well-matured compost adds organic matter and nutrients that improve the soil.  So without knowing more about your soil, I would guess on the 'better to add' side of the equation.  Be careful with manure: first it has to be well-composted and secondly, sometimes we see high phosphorus and potassium levels in manure.  This is all guesswork without a full soil test.

I hope this helps!  Wishing you healthy soil and a joyful gardening season,

- Robilee Smith

Robilee Smith Replied April 15, 2021, 1:30 PM EDT

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