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The Importance of Garden Soil: Understanding Your Soil Type and Its Health

First of all, what is soil, exactly? Soil is the loose surface material that covers most land. It consists of inorganic particles and organic matter. Specifically, 45% of soil is made up of clay, sand, and silt minerals; 25% is air; 25% is water, and 5% is organic matter (like dead and decaying plants and insects, as well as manure).

Every soil composition is different and depends on location, weather, geology, and what the soil is being used for, among other things. Some soils have more clay or sand and more or less water, for example. The ratio of the materials makes a big difference in the quality and makeup of the soil. All plants are different, but most gardens love “loamy soil.” This is 40% sand, 40% silt, and 20% clay.

The sides of the triangle are the percentages of sand, silt, and clay. Clay percentages are read from left to right across the triangle. Silt is read from the upper right to lower left.

The essential role of your garden soil 

What does soil do in your garden? What’s it’s purpose?

1. Soil provides structure and a growing medium for plants.

Soil allows roots to anchor themselves within the soil’s structure so that plants can grow up strong, tall, and healthy without falling over. It is possible to grow plants out of the soil, but they need some kind of structure in which to be supported.

2. Soil regulates water and oxygen supplies within your garden.

Soil regulates water and oxygen using micro- and macro-pores. For instance, sand offers more macropores, allowing water and air to flow right through it. While clay offers more micropores, essentially holding water and air in place. Each has its benefits and downsides.

3. Soil is a natural recycler of organic matter

Decomposition in the soil breaks down dead and decaying plant and animal matter into useful nutrients, like nitrogen, phosphorus, and potassium. All of these are vital macronutrients for plant health.

4. Soil provides a habitat for organisms and insects

There is so much biodiversity in the soil, from the insects you can see to microscopic organisms, such as mycelium, that play a vital role in balancing the ecosystem beneath our feet.

Understanding your garden’s soil type: Test time!

How do you know what kind of soil you have in your garden? There are a few simple (and fun!) tests you can try at home. Here are a few:

Mold test:

Grab a handful of dirt and squeeze it in your hand. If it holds a shape when you let go then it has a good amount of clay. Drop it on the ground. If it breaks apart, then that’s a good balance of sand to clay. However, if it bounces and holds its shape, then you have high amounts of clay.

Fingertips test:

Rub your soil between your fingertips. How does it feel? A grainy feel means sand, a silky smooth texture means silt and a sticky feel means clay.

Colour test:

What colour is your soil? If it is grey/light brown, then it means low levels of organic matter. When you dig in if it is grey and even blueish, then you have high clay, and very compacted soil, and no oxygen is flowing. The goal is for dark brown/black soil, which means there is lots of organic matter present. 

Smell test:

Does your soil smell earthy? Perfect! If you smell eggs when you dig, then that is compaction which means that oxygen hasn’t been able to flow through the soil.

Organisms:

Do you see insects in your soil? If you do, that’s great. This means there is organic matter and microorganisms working and living in your soil. If there is nothing, then your organic material levels are low, as there is nothing for the organisms to feed on. (Time to add mulch and compost!)

What are the most common soil issues in a garden?

1. Compaction

Heavy rain, winter freezing and snow, and lots of foot traffic all add to your garden’s soil compaction. If you (or your gardener) are working in your garden beds a lot, then your weight is compacting the soil beneath you. This reduces the pore space between your soil’s particles. Compaction causes poor water and oxygen flow, which means that roots can suffocate and struggle to get the nutrients and air that they need to thrive.

2. Depletion

Fallen debris and organic matter on top of your soil break down into the soil. But if you remove that organic material and you aren’t replacing it with mulch at least once a year, then your soil is slowly depleting. Your plants use the nutrients from the soil to thrive. Over time, the nutrients become depleted, especially if there is no organic matter breaking down to replenish the soil.

3. Poor soil to begin with

Sometimes, garden beds are built with poor soil or just a thin layer of topsoil, to begin with. This sometimes happens during construction when the dug soil from underneath the foundation is merely dumped into the garden. This means that the soil lacks nutrients and structure right from the get-go and will be an uphill battle thereafter.

Signs and symptoms of poor soil health in your garden

What are some of the signs that your soil needs replacing or help to improve?

Stunted growth or dead/dying plants

Lack of movement of nutrients, water, and oxygen in the soil can lead to a lack of growth in plants, and even death, as they are starved of what they need to grow. Diseases like root rot and vascular wilt are common in poor soils.

Excessive weeds

Weeds like to show up in some unlikely spots, and this is because they can handle poor conditions that most plants cannot. Have you ever wondered why dandelions show up in a path through your lawn that you walk regularly, but the grass struggles to take in that same path?

Cracking soil

Moisture in the soil causes the layers to expand. But when the moisture is gone, the soil literally cracks, like a dry desert. This highlights poor moisture levels within the soil, and it is due to the structure not being suitable, therefore the plants won’t get the moisture they need.

Poor tilth

If digging in or tilling your soil is really difficult and the surface is crusty and hard, then you have a soil tilth problem. You may notice that the soil is compacted and dry, and the color is grayish-light brown as you dig deeper. If you are struggling to get a shovel through the soil, then how is a plant supposed to send roots out in search of nutrients and water?

What you can do about poor soil health

Mulch, mulch, mulch! If you have read any of our other gardening blog articles, you will see that we talk a lot about mulch. That’s because it is super important. Mulching your garden beds is the best way to improve your soil’s health. It takes a few seasons of adding mulch and allowing it to break down naturally over time to restructure and rebalance your soil completely.

Here is how mulch helps improve your soil health:

1. Boosts soil structure: The mulch breaks down into the soil, giving feed to the organisms, which work in the soil and burrow through amending the structure of the soil as they work.
2. Adds nutrients: The organisms eating the organic material in the mulch, then defecate and the nutrients in this new form are able to be absorbed by the plants.
3. Protects your soil: Mulch helps protect the soil from compaction, as all the factors causing compaction impact the mulch layer, and reduce the impact on the soil below.
4. Retains water: By shading the soil, it helps to retain soil moisture, reducing the amount you have to water by as much as two-thirds
5. Maintains soil temperature: Similar to water retention, the mulch shades the soil during the hot months, but also keeps the soil warm during the colder months.
6. Looks great!

Other ways to improve your garden’s poor soil health

Replacing the soil as a whole is always an option. It is a laborious task to remove large amounts of fill, but if you’re wanting to refurbish your garden and are in need of a quick remedy, dig it out and bring in better topsoil for start a fresh.

Planting more plants is another option. This route still requires mulching, though, and planting the right plants in the right places. The more big open spaces you have in your garden beds, the more issues you may have. Here’s why.

Think of your garden as a habitat and mini ecosystem

More plants mean more organic material, protection, and shelter for smaller, important insects and bugs. More flowers and pollen brings more helpful pollinators. Plants catch, absorb, and hold more rainfall too. They shelter the soil below from harsh elements like too much sun or heavy rain. Plant roots improve your soil’s structure and invite other organisms into the soil regeneration cycle.

What are the different types of mulches available?

Mulch is a material applied as a layer over the surface of the soil, for the function of one or more of the following: weed suppression, moisture retention, temperature regulation, nutrient supply, and/ soil structure support. Mulches are mainly organic, but there are non-organic mulches that can be used, and serve a purpose in certain circumstances.

Still unsure about your garden’s soil health? We can help!

Bring in a professional gardening company, like our expert gardeners at Costa Verde in Victoria, BC. We’re here and happy to help! We can analyze your soil, investigate why your plants aren’t doing well, and make suggestions of steps to improve the health of your garden.

Learn more about Costa Verde gardening—and book a free garden visit.