Simple DIY Garden Soil Analysis and Testing

Closeup on garden soil and neem granules

Our new home garden is actually a very old garden that has been both loved and neglected over its many years of cultivation. When we arrived, many of the plants were dead or on the brink of dying. With a lot of hard work (and a little specialist help pruning, felling, and chipping), we cleared back to a healthy skeleton. Then we set about a year-long effort of nurturing the soil to be ready for planting the following winter/spring. We did our own basic soil analysis using simple DIY soil testing methods. Here’s the dirt on how to check your own garden soil.

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On the subject of new/old gardens, we’ve moved yet again since this post was first written and shared. We now have a completely different garden location, type, condition, and soil. But the same soil assessment principals below still stand and they’ve been helpful in understanding and working to improve our heavy clay soil. Wish us luck! It’s a garden battle…

Assessing Soil Structure

Sometimes you can judge a garden’s soil just by looking at it. Crackled dry clay is a classic, and an unwanted classic at that for most gardeners! In many cases, it’s tricky to judge soil from the surface, especially if the ground is covered with plants or mulch. For a deeper look (literally), dig a clean-sided hole approximately 30cm deep and check the soil structure. 

  • If your soil is mostly subsoil or low-quality fill then you need to consider augmenting/replacing soil or using raised beds. This is a common issue around new building constructions.
  • If there is a reddish-brown borderline running under your topsoil, this is called hardpan or ouklip. It’s not a bad thing, just a sign that the garden might benefit from a little help. Hardpan is a layer of deposited material and/or compacted soil, and will need to be broken up as part of prepping your soil to ensure that water and fine roots can all work their way through the ground as your garden gets established. 
  • If you have thick clinging muck (wet) or rock-hard impossible to dig (dry) ground, you might have the misfortune of heavy clay. Bummer. Yeah, we feel your pain. See below for info on checking soil type and drainage. We have a full post on clay, too.
  • If you have really loose and sandy soil, adding some organic matter like compost can help improve the soil quality for better nutrient access and growing conditions. 
  • If you have good looking workable topsoil, great!

Sniffing Out Trouble

While you’re out there digging, be alert for unusual smells. Unhealthy soil can have a definite stink about it! Normal fresh soil smells, well, earthy. Sour or rotten smells are a sign that something is off-balance, and can indicate that your soil is anaerobic (lacking oxygen). This is common in heavy soils, like clay, that are oversaturated. 

Cracked muddy clay soil

Checking Soil Type

Squeeze and roll a damp handful of soil in your hand. If it forms a solid sausage-like shape and holds form when you touch it, the soil is clay. If it is gritty and crumbly, it is sandy. If it holds, but then quickly crumbles to the touch, you have loam.

You can supplement this check by dropping your handful of soil into a glass or jar of water. Mix thoroughly, then leave it to settle for an hour or so.  Stones and sand will quickly settle. Fine particles like clay and silt cloud the water and will take a long time to settle. Organic materials will often float.

Analysing Soil pH

You can easily test your soil pH with an inexpensive kit (litmus style testing) or tester from your local gardening supplier or online. I opted for a simple soil pH tester (affiliate link for example products), which allows me to quickly and easily test multiple locations of the garden periodically. Knowing the pH allows you to either select plants for your soil type or adjust the soil to suit your plants.

I was surprised to discover that we have neutral soil – in our area, most soils are slightly acidic. Our used coffee grounds having been making their way to our acid loving plants ever since, but this is a minor influence at best. I find it does help keep neighbourhood cats from leaving “presents” though! We will need to make special pH adjustment provisions for acid-lovers like our big old camellias and parts of the new berry patch.

DIY soil pH tester in a garden bed

Looking for Signs of Life

Take a look around you garden for signs of life. This might require channelling you inner child (or get the kids to help!) as most ground insects prefer dark areas. Look under leaf-litter, stones, etc or dig a small shallow hole, and ensure that you have a thriving insect community. The creepy crawlies, along with less visible fungi and bacteria, help to break down organic reside, reduce the risk of pests and disease, and make nutrients available to your plants. 

You can also do a quick earth work check by digging up a shovelful of soil and looking through it for worms. A healthy worm population is a sign that your soil has good organic matter on which to feed.

Testing Soil Drainage

Before you refill that hole from your initial soil assessment, make sure its around 30cm deep and 15cm wide, and then fill it with water. Allow it to drain and rest overnight to ensure that the soil isn’t unusually thirsty when you do your test. If it hasn’t drained overnight and rain isn’t to blame, either you have very wet ground or very heavy clay. Hopefully not the case!

The next day, refill it with water and measure the rate of drainage on an hourly basis. Drainage of around 5cm/hr is ideal. If your hole drains very rapidly or very slowly, you may want to make adjustments to the soil or planting selection, or build a raised bed.

Testing Soil Absorption

In our garden, we had the additional problem of having some water-repellent (hydrophobic) areas.  Adding a lot of extra soil, compost, and/or soil wetters were not suitable for our soil type and location, and it would have cost a lot to buy enough to work through all of those garden areas. So instead we set about the long slow process of using a cover crop through the winter and working to increase microbial activity before getting on with replanting the new garden.

If you’re concerned about your soil’s absorption, you can observe how long it takes a water drop to absorb. It’s a quick and easy DIY soil test.

  • If it immediately absorbs (less than 1 second), great! 
  • If it takes less than a minute, your soil is still absorbing moisture at a reasonable rate. If it’s at the upper limit, you might still want to proactively work on the soil condition. Adding some compost or using mulches can help.  
  • If it takes over a minute, then consider working to improve your soil’s absorbency.  
  • If it still hasn’t absorbed after a few minutes, consider treating for hydrophobia. 

We didn’t need an absorbency test. Our problem was readily apparent. Water (rain or applied) on problem areas would simply bead on the soil, roll around in little dirt coated droplets to the lowest point, and then just sit on the surface.  Not good at all! 

Absorbtion in Pots and Planters

In pots and plants, absorbency can be trickier to spot. When you water your plants, the water might not be sitting on the surface, but instead of soaking into the soil, it’s just running straight through and out the sides and/or drainage holes. A few classic signs of trouble to watch out for are rapid run-through, plants that always seem thirsty even if they’ve been watered or it’s just rained, and pots that don’t seem to get heavier when the soil should be full of water weight. 

Other Garden Soil Testing Considerations

Soil Contamination

In some locations, particularly (but not limited to) older sites or long-established areas, soil may carry trace contamination from old metal roofing, lead paints, and any number of legacy factors. If this is your situation, as a precautionary measure, you may want to research additional testing options in your local area before planting an in-ground edible garden.

Soil Nutrients

If you need a more comprehensive understanding of your soil, check for local laboratory testing services. They take a drop-off and/or mailed soil sample and provide you with a detailed break-down.

Simple DIY Garden Soil Analysis and Testing

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