Soil that’s too acidic or too alkaline can create a challenging environment for crops to grow. Here’s the easiest way to test soil pH and amend it organically.
One of the last things you might think about in your edible garden is testing soil pH. Generally measured on a scale from 3 to 10, soil pH, or ‘Potential of Hydrogen’, tells you how acidic or alkaline it is. The reason that you should keep an eye on it, is that if the soil’s pH is unbalanced, then there’s a strong chance that your plants will struggle.
Fortunately, I’ve found the easiest way to test soil pH and can recommend things that you can do to make the soil more hospitable to garden crops. You can test soil pH at any time of the year but autumn can be the best time. It will give you over the winter to correct your soil’s pH before the new growing season begins.
The easiest way to test soil pH
Over the years I’ve hauled in and added a lot of manure and compost to my garden soil. Both help to improve my clay soil’s drainage and structure and help create a nurturing medium for soil organisms and plants to grow in. Still, I wondered if the manure had made my soil more acidic over time so I invested in a new pH meter. It’s so easy to use! You literally push the prongs down into the ground and the display at the front tells you the soil’s pH. Fortunately, mine was a neutral 7 so I won’t have to amend with garden lime as I’ve done in the past.
Traditional Soil pH Kit
When I started my first allotment garden over seven years ago it was a blank slate — literally a rectangle of grass outlined by blue baling twine. The first thing I wanted to do was slice into that turf and make the ground ready for immediate planting. Visions of sweet corn, artichokes, and strawberries spurred me on.
It was only about halfway into digging it over that I decided to test the soil’s acidity. It was clay which generally means acidic but I didn’t know by how much. To find out, I bought a traditional pH kit which includes test tubes and a chemical solution to mix with the soil. After fiddling with it out in the field I managed to get the soil inside the tube along with the liquid and powder. The end result was a pH of 5.5. Acidic, but not overly so and simple amendments could sweeten it up relatively quickly.
Unbalanced soil = Nutrient Deficiency
The issue with soil that has a pH of 3-5 is that it makes it difficult for plants to absorb nutrients. The more acidic the soil, the more plants struggle to get the nitrogen, phosphorus, and potassium that they need. It can be there in the soil, but the pH affects how easily plants can absorb it. If they can’t absorb it, they can weaken and even die from nutrient deficiency. The same can go for soil that’s too alkaline (pH 8.5-10). You’ll find it’s mainly chalky soils that fall into this category.
Organic Soil Amendments
Vegetable gardeners aim for their soil to be between pH 6 and 7. If it’s not in that Goldilocks zone, changing the pH can be done organically by adding garden lime, wood ash, or mushroom compost to increase the pH — all three make it more alkaline. You can also add sulfur to lower the pH and make your soil more acidic. If manure isn’t completely composted, it can also acidify garden soil, but it can be too inhospitable for young plants to grow in. Fresh manure contains types of salts that are broken down in the composting process. Without being composted (aged) first, manure can burn young plants.
Keep in mind that it’s a lot easier to ‘sweeten’ the soil than to acidify it. The most common way of raising the pH is to add handfuls of garden lime to your soil in the autumn. Over winter it breaks down and gradually your soil’s pH will increase. You can also add garden compost and well-rotted manure to acid soil to help break it up and stabilize the pH. No matter your soil type, it’s always a good idea to mulch at least once a year with compost.
Finely ground sulfur is used to make alkaline soil more acidic. The way it works is that soil organisms convert the original sulfur into sulphuric acid, thus lowering the pH. It sounds a bit eyebrow-raising, but this method is the least harmful to plants according to the RHS.
Sulfur can take weeks to see initial results and is actually part of a longer-term solution. All the while, the limestone in naturally alkaline soil will continually break down and make the soil alkaline. This means that you’ll have constant work in adding amendments to keep it from tipping back to alkaline. Amendments include sulfur, but also garden compost and well-rotted manure.
Grow Acid-loving or Acid-hating plants
The other option you have is to grow plants that love your soil as it is. Blueberries and cranberries love acidic soil as do raspberries and potatoes. If you have alkaline soil there are veggies for you too. Asparagus, cucumbers, and alpine strawberries will all thrive in soil that other edible plants won’t like. There’s a great table of garden veg that love acid or alkaline soil over here for you to continue your research.