Taking a soil survey of your garden sounds a little intimidating, but it is an essential part of the planning and maintenance of your garden.
Your soil type will help you choose the best plants suited for your garden, and once you know what you have under your feet, you can plan what you need to do to improve your soil.
Identifying and improving your soil will not only increase your garden’s health, but you will be doing the planet a favour too.
Plus, this simple process is a fun exercise, like being back in primary school science! It is not expensive, no ph tests or trace minerals kits are required. Nevertheless, this simple soil survey will deliver insightful information that will help you decide what to grow where.
How to do a Simple Soil Survey
You will need
- Large clean jars with a lid. I’m using recycled 680ml passata jars.
I am going to survey a patch of soil that has been largely ignored, and the soil I have in my raised garden beds.
Move aside any mulch and scoop about a cup’s worth of soil into your jar.
Fill the jar with water, secure the lid and shake it. Already, you can see the sandy soil quickly settling on the left. My amended garden soil from my raised garden beds is on the right.
Place it on a bench and leave it for a few hours.
While we wait for our soil survey results, let’s have a chat about soil types.
The Five Main Soil Types
There are five main soil types, sandy, clay, peaty, chalky and loamy.
If you have sandy soil, you will see heavy particles sinking and forming a layer on the bottom of the jar almost instantly. The water will also appear fairly clear. Sandy soil is typically alkaline, free-draining, and as a consequence, is almost always nutrient-deficient.
Sandy soil type can be amended by applying clay and incorporating compost. Be especially cautious using soluble fertilisers on sandy soil. Often, there is very little uptake by the plants (as the nutrients drain away too quickly) and the soluble fertilizer can pollute groundwater.
If you have clay soil you have likely had a clue when gathering your sample! Clay soil can become compacted and be difficult to dig.
You have clay soil if your sample contains cloudy water with only a thin layer of dirt particles on the bottom. The water stays cloudy as tiny clay particles take longer to settle. Silty soils behave in a similar way. Clay soil does not drain well and may cause problems with waterlogged plant roots or stunted root growth.
Clay soil type can be amended by digging through gypsum and incorporating compost. Introducing earthworms into the soil will help to break up the soil.
If you live near a marshy or swampy area, you will likely have peaty soil.
Your soil sample will have a bit of debris floating on the surface with only a small amount of sediment on the bottom. The water may be brown and murky. Peaty soil is almost entirely organic, acidic and is prone to waterlogging. Frankly, peaty soil can smell a bit funky too.
Peaty soil can be amended with the addition of clay to soak up some of the moisture and give structure to the soil.
Chalky or limey soil will leave a layer of white gritty bits at the bottom of the jar. The water will be cloudy and pale as well. Like sandy soil, chalky soil type is alkaline, free draining and offers very little nutrient to plants.
You can amend chalky soil with the addition of a little clay, and compost.
If your soil sample has clearish water with a layered sentiment of sand on the bottom with settled clay particles on top, then congratulations, you have hit the soil jackpot! Loamy soil type is an equal, balanced blend of sand, clay and organic matter.
Plants will thrive in loamy soil as it is highly nutritious, retains water well, yet is friable enough to allow healthy root development.
BONUS 6th Soil Type – Hydrophobic Soil
Hydrophobic soil is downright bad news. Hydrophobic soils repel water. All kinds of soil can suffer from hydrophobic soils, even so-called free-draining soils like sandy and chalky soils.
Perhaps ironically, when soils dry out, they can become hydrophobic and difficult to re-wet. You will recognise hydrophobic soil the minute you try and water. The water will pool on the surface without soaking through, or drain away quickly.
As you can see in my own garden above, this soil is hydrophobic. Despite it being a rainy day, the water has only penetrated a few millimetres below the soil surface and the soil underneath is dry.
Hydrophobia can be especially evident in pots, when water just drains out of the pot as fast as you pour it in.
To amend hydrophobic soil, you may need to apply a soap-based surfactant that will temporarily dissolve the repellant bonds between particles.
But the best way to treat hydrophobic soils is to prevent the soil from drying out. Mulch soil well, although avoid using pine or eucalyptus based mulch, the oils in these mulches can sometimes contribute to the problem.
The Truth About Soil Health
Now you know what kind of soil you have, you can work with it. Blueberries love acid soils, where carrots and capers can handle sandy and chalky soils.
Plants are an essential part of creating healthy soil, but it is a catch 22 situation.
Healthy soil needs healthy plants and healthy plants need healthy soil.
Soil amendment takes time, years even, but is well worth prioritizing in your garden. I work this soil survey into my garden care routine every season to ensure I am constantly improving the soil and to identify my problem areas.
One of the best amendments you can make is the addition of compost and worm castings that add beneficial nutrients and microorganisms to your soil. So if you arent already composting or worm farming, now would be the perfect time to start!
Healthy soil is the very foundation of a healthy, sustainable garden. You simply can not raise healthy plants in unhealthy soil.
So what were your soil survey results?
My soil is indeed sandy. The sample on the left is raw soil from my garden, the one on the right from my raised beds that is regularly amended with worm castings, clay, rock minerals and well mulched with lupin mulch. Look at the difference!