Use a pH Probe for Testing Soil pH the Easy Way

Hi, I’m Stephen of Alberta Urban Garden dot CA. The pH of your garden soil is an important factor that can often be overlooked. The pH in your garden soil can impact the availability of nutrients within that soil and your plants ability to take them up. If you’re growing in a soil that’s not optimal for the plant often you can sacrifice all of your harvests or if your plant does produce it’s going to look very stressed and produce significantly less.

On today’s joint episode between the Testing Garden Assumption series and the Urban Gardening Series I’m going to take a look at the impact the pH can have on your garden, how you can easily measure it yourself and how you can amend it over time.

If need be pH is measured on a fourteen point scale with zero being the most acidic seven neutral and fourteen the most basic. Most common garden plants prefer a slightly acidic or neutral soil. There is a link in the description to the University of Vermont’s reference page outlining the optimal pH for a number of common crops.

There are two common ways that you can measure the pH of your garden soil. The most accurate way to learn the pH of your soil is to run a sample through a lab like Maxim Analytics or a university extensions office. You can measure the pH of your garden soil yourself, however this method is far less accurate but it should give you a good indication if you’re roughly in the right range or not.

Use a pH Probe to Test pH

In order to measure the pH of your garden soil at home you’ll need two things. The first is a pH meter, I got this one for under $20 and it should be accurate enough for my purposes. The second is deionized or distilled water. You can pick this up in most drug stores and it has a neutral pH whereas your rainwater may be a little acidic and your tap water is a little basic which can throw off your results.

The pH of your garden soil will shift throughout the year and from spot to spot. This meter is not nearly as accurate as the ones that they have in the lab. However, if you increase the number of sampling points you take you should increase the reliability of the results you get.

For this roughly 1 meter by 1 meter bed, or 3 by 3 foot, I’ve selected four spots that are representative of the bed. The more sampling locations you measure the more accurate your numbers will be. Pull back the mulch and the top two to three centimeters or one inch of the soil. Most roots are below this initial area and the mulch that I use to cover it over the course of this season can temporarily impact the soils pH. Mix the soil in the hole down to six inches or 15 centimeters making sure that it’s as close as possible to a consistent mixture or homogeneous. Flood the area with your deionized water this will help the meter get a proper reading of the soils pH. Turn on the meter and make sure that the probes are clean. Insert it and wait for one minute until you take your reading.

Record the reading and repeat at your other sampling locations. Once you have finished up, average the readings. That is the most representative pH of your soil. If your pH reading is within the range for that particular crop you can rest assure that the pH won’t cause any issues for your crop and is unlikely to change significantly.

Over time, one of the most common mistakes that new gardeners make is to apply a store-bought fertilizer to try to fix a nutrient deficiency without knowing if that’s actually the issue. As I mentioned earlier the pH can affect the availability of the nutrients within the soil and the ability of the plant to take it up. This may be when you need to take a look at the pH of your soil and if you need to amend it over time. If the pH of your soil is very low and you need to raise it, gypsum or lime can be added to bring that pH back up.

If the pH of your soil is too high and you need to lower it, you can add elemental sulfur or flowers of sulfur or simply mix in peat into your garden soil. Compost that is made with a higher carbon content such as leaf mold does have a lower pH however it is not as effective as peat or elemental sulfur for lowering the pH of your soil but it does make up a good base that maintains an initially lower pH.

There are quite a few myths related to lowering the pH of your soil. Amendments such as cold coffee and pine needles themselves are acidic, however, too weak or neutralized before they can transfer any acidity to your soil. If you do need to amend the pH of your garden soil in order to bring it into the correct range you’ll likely need to continue to do this over time as the soil will return to its original pH if left alone. This is through what’s called the buffering capacity of soil. Essentially chemical reactions in the soil will eventually return it to that original ph if left alone.

Quick pH changes of over one point can have a devastating effect on the plants that you’re growing. Quick shifts in pH can destroy the microorganisms that run the nutrient cycle in your garden. If you do shock the organisms in the soil that run the nutrient cycle, your plants may struggle to take up any nutrients especially if that quick shift in pH has burned the plant’s roots. If you are going to amend the pH of your soil make sure to take it slow. I usually recommend doing one treatment a month during the growing season and measuring the pH before and after each treatment.

Starting with the garden soil that has a pH that’s already within the optimal range for the plants that I’m going to grow is one of the main reasons why I chose to grow in raised beds. It helps me control the pH from day one and this allows me to avoid the cost of testing and amending the soils pH over time.

I started most of my garden beds with a soil that contained a high component of compost. And where I knew that I would have acid loving crops like my lingo berries and blueberries I add mix peat into it to keep the initial pH much lower.

Peat is a non-renewable resource and I like many of you like to avoid using store-bought products within my garden. However, I did need a soil that had a lower pH for a number of my crops. So I weighed my options. I could either use peat which is a waste product here in Alberta or I could use elemental sulfur which is also non renewable but shipped here from other places and continue to use it for the life of those plants. I do however recommend if you are going to make these decisions you do your research and you make your own decision. Don’t take my word on it, please.

If you’d like to learn how to grow more food at home or learn about other garden myths check out the links on screen now and make sure to subscribe to get all the future episodes in these two series.