How to Turn Bad Soil into Good Soil

If the crops in your vegetable garden fail to thrive, it may be that you have a soil problem. It could be too dry, too sticky, too compacted, or lacking nutrients. Fortunately, it can be easily corrected using a simple organic gardening technique. Becky Searle, author of Grow a New Garden, shares how to turn bad soil into good soil so that your garden can become a lush and bountiful growing space.

At the very center of everything we do in our vegetable gardens is the soil. It’s the foundation from which everything grows and is the main difference between a healthy garden and one that is constantly struggling. Most of us know instinctively if we have poor soil. The first clue is that our plants don’t grow very well. If you’re confident that you have the right plant in the right place and have given it what it needs, but it still fails to thrive, the problem is most likely with the soil.

But what is the difference between poor garden soil and good? Can we change what we have, or must we learn to live with it? I have some good news to share, and whether you are growing a new garden or improving your existing space, it all starts with what’s under your feet.

What’s Your Soil Type?

For generations, gardeners have been taught that their soil is either sand, silt, clay, or somewhere along the spectrum between these. The most hallowed of all soil types is loam, which is approximately 20% clay, 40% sand, and 40% silt. We can tell what soil we have by doing a simple soil test.

It involves rolling a ball of moist garden soil taken from an inch or so down. If the ball stays together well but crumbles when you pinch it between your fingers, it’s probably towards the sandier side. If it stays together well and doesn’t crumble when pinched, you have clay.

Another way to tell is how the soil looks in different conditions. If it’s sticky and slippery in winter and dry, hard, and cracked in summer, it’s clay. If it’s dusty and light and digging into it is a breeze, you likely have something sandy or silty. If the latter is gritty, it’s probably sandy; if it feels light and floury, it’s probably more comprised of silt.

Knowing what type of soil you have is important, but only so you can make good choices on what to grow. Some plants will not thrive in some soil types, and whilst all soil can be improved, you cannot fundamentally change its consistency. So put away the bag of sand for your clay soil—it won’t make a difference. But fear not, because I’m here to tell you what will.

Achieving Moist, Well-Aerated Soil

Read almost any plant label, and it will tell you it wants moist, well-aerated soil. Or rich, moist soil. Or moist, well-drained soil. It’s all the same story. Drainage and moisture retention seem to be two things on opposite sides of the spectrum, so achieving both might feel a bit of a feat. But I can assure you it’s much easier than you think. All it takes is an understanding of how soil structure works.

The ground beneath our feet is not one solid chunk of dirt. It’s a complex and living structure built by the extraordinary community of organisms living within the soil. Most notably, bacteria and fungi. They turn dead leaves, wood, and other materials from plants (sugars and carbohydrates) into sticky organic glues. These glues bind sand, silt, and clay particles together.

You may think that sticking them together is the last thing you want, especially if you have experience growing on clay. However, when the particles bind with these organic glues, they form irregular shapes called aggregates. Then, things like earthworms tunneling within the soil open spaces between these aggregates called pores.

The aggregates act as tiny subterranean sponges, holding onto water. At the same time, the pores help water to travel down through layers of the soil, and as it does, it creates a vacuum, pulling air in. That’s how we can get moist, well-aerated soil.

Soil Life Creates Healthy Soil

Life in the soil consists of a dazzling array of creatures. Worms, of course, but most of the hardworking little organisms in the soil are hidden from the naked eye. There are bacteria, arthropods, mollusks, nematodes, protozoa, fungi, and much more living in the ground beneath your feet.

They pull dead organic matter or humus from the surface down into the soil, which is how autumn leaves seemingly disappear before spring. This action feeds soil life, along with carbohydrates and sugars pumped out of plant roots. They access them through root exudates, which are formulated by plants to feed life in the soil.

In exchange for dead plant matter and nutrients from living plants, soil life creates good soil structure, releases nutrients to our plants without the need for fertilizers, and acts as a first line of defense against pests and pathogens.

Why? Because the life in the soil relies on our plants to survive. Soil actively wants plants to thrive so that they can thrive, too. Plus, the organisms in the soil will also thrive in a moist, well-drained environment.

How to Turn Bad Soil into Good Soil

There is one key ingredient that turns bad soil into good soil, and that is organic matter. In nature, the soil is fed annually by leaves falling to the ground in autumn. They are broken down and incorporated over the winter. During the summer, organisms feed on nutrients taken from plant roots.

The trouble is that we often clear away dead plant matter to keep our gardens tidy or take away vegetables from our gardens to eat them. So, to ensure that the soil organisms can go about their valuable work of creating healthy soil, we must feed them.

How to Feed the Soil

To do this, we only need to add back organic matter. However, if we throw a load of grass clippings, sawdust, straw, dead leaves, or vegetable debris over our garden, we will likely encounter pest problems—things like slugs, woodlice, and possibly even vermin.

So, to keep it tidy and pest-free whilst still feeding the soil, we use compost or manure. The best way to add it is to spread it over the soil’s surface as a mulch. Organisms can then naturally come up to feed and bring nutrients down into the ground.

The Best Type of Organic Mulch

The best mulch to use in your garden is whatever you have available and can afford. However, if you have a choice and want to improve your soil, some can be better than others.

If you have heavy clay soil, you might opt for a woody compost, rotted wood chips, or a standard multi-purpose compost. A soil improver or well-rotted animal manure would be the better choice if you have sandy soil. Woody compost will help aerate your soils while soil improvers and manure add nutrients.

Homemade compost is an excellent resource if you have or can make it. The wonderful thing about homemade compost is that it will contain the exact balance of nutrients your plants needed last year—nitrogen, potassium, phosphorus, and even calcium. So, you can recycle this back into the soil, like a personalized nutrition plan.

Consequences of Traditional Digging

Traditional gardening wisdom tells us to dig, or even double dig, our soils to loosen, aerate, and incorporate organic matter. However, the debate about whether to dig or not has been one of the most discussed topics in horticulture in recent years.

From what you have just learned about how soil works, you may already have an idea about the preferred option from a scientific point of view. But what actually happens if we do dig? We are, of course, talking about digging over soil, not simply digging a hole to plant into.

When we dig over our garden beds, it creates a burst of nutrients and loosens the surface of the soil for planting. That’s how digging became popular in the first place.

However, the burst of nutrients comes from many of the microorganisms in the soil dying as they’re exposed to UV light. Light also causes the glues in the soil to break down, releasing back into the atmosphere as carbon dioxide. This means that the structure will be back to where you started by the end of the season. Ironically, digging can even lead to compaction over time by creating a hard pan.

How to Practice No-Dig Gardening

So, if you want to build the long-term health of your soil and, in turn, your plants, practice no-dig gardening. The basic premise is simple, and all you need to do is:

• Spread compost or aged manure on your soil as a mulch. Do this once a year if possible, or every few years if not. Don’t use more than a few inches (7 cm) at a time to avoid nutrients leaching out. It’s best to do this at the start or end of the growing season.
• Try not to disturb your soil. Dig when you need to plant into it or remove large weeds, but otherwise, try to leave it to do its own thing.
• Make your own compost. Recycling the plants in your garden is the best way to ensure you have plenty of mulch and grow happy plants.
• Plant a diverse range of plants, each of which will help to build a diverse community of soil life. Crop rotation with no-dig gardening isn’t necessary, but it will help to prevent the build-up of pests and diseases.
• Keep the soil covered with plants as much as possible. Using green manures and cover crops over the winter can help with this.

Grow A New Garden

If you want to learn more about soil or how your garden works as an ecosystem, my book Grow a New Garden covers this in detail, turning you into your very own gardening expert.

• How to Design a Vegetable Garden Layout
• 70+ Perennial Vegetables to Plant Once and Harvest for Years
• Grow a Container Vegetable Garden