Simple DIY Garden Soil Analysis and Testing

Closeup on garden soil and neem granules

Our new old garden has been both loved and neglected over its many years of cultivation. When we arrived, many of the plans 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 (now in our hemisphere). We did our own basic soil analysis using simple DIY soil testing methods. Here’s the dirt on how to check your own garden!

Mini update: We’ve moved yet again. 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 often 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 fill then you will 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 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 work their way through the ground.
  • If you have thick clinging muck (wet) or rock-hard impossible to dig (dry) ground, you might have the misfortune of heavy clay. Bummer.  See below for checking soil type and drainage.
  • If you have good looking workable topsoil, great!

While you are 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. 

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 pets 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 clay and/or soil wetters were not suitable for our soil-type and location, so we instead set about the long slow process of using a cover crop and working to increase microbial activity.

If you are concerned about your soil’s absorption, you can observe how long it takes a water drop to absorb.

  • If it immediately absorbs (less than 1 second), great! 
  • If it takes less than a minute, you soil is still absorbing moisture at a reasonable rate.
  • 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 sit.  Not good at all! 

Other Garden Soil 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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