Heavy clay soil is every gardener’s worst nightmare. It retains water longer than it should, and it’s too dense to allow the root systems of the plants to develop properly. But there’s no reason to give up on your gardening dreams just because the soil in the garden has a dense texture and heavy structure. As mother nature would say, this is not a bug, it’s a feature. So one way of working around the shortcomings of your clay soil is to change the way you look at it.
There’s no such thing as perfect soil. Even the richest and loamiest of soils lose their light texture and nutritious content the more you grow plants in them. So rather than see your clay garden as a barren waste, you can work on amending it and improving its texture and structure. Luckily there are many ways you can achieve this to render your soil more arable and plant-friendly. Read on to find out how to identify your clay soil, what you can do to improve it, and how to maintain it.
All About Clay Soil
To identify any type of soil, you need to look at its texture, structure, and tilth. So what are those three elements, and how would you use them to identify and amend clay soil?
We start with the soil texture. Usually, the texture of the soil is determined by the amounts of clay, silt, and sand particles in it. If the soil has a more prevailing element of those three, then it will determine its texture and type. More clay particles in the soil make it heavy and dense. It turns to clump easily in your hand and has higher water retention than normal. Neither of those two qualities is instrumental in healthy plant growth.
The soil structure describes how the particles are arranged. This is an innate quality of the soil that you can do little to change. In the case of predominantly clay soil, the clay particles are arranged in the form of dense horizontal layers. When the layers get stacked on top of each other, it creates compact soil that acts as an impenetrable shield. The roots of the plants find it hard to penetrate this soil and achieve their full development.
As for the soil’s tilth, it indicates how tillable the soil is. This quality is important in determining the value of the soil as a seeding bed and how easy it is for the seedlings to emerge out of the soil. Once again, clay soil has bad tilth, and germinating seeds might struggle to breach the soil surface and establish their roots below.
Clay soil usually scores badly in all of those three categories. It tends to crust, doesn’t aerate well or drain at a good rate, and readily turns into clods. And you’d want the exact opposite out of your soil if you expect your plants to grow successfully and prosper.
The Upsides and Downsides of Clay Soil
Despite that bad rap that clay soil has, it’s not exactly without merits. So before you turn up your nose in disdain at your clayish garden, remember that you can’t have a plant growing in purely sandy soil either. That type of soil doesn’t hold moisture enough for the roots to absorb it, nor doesn’t provide a solid ground to keep the plant standing upright. So let’s go through the advantages and disadvantages of clay soil to better understand how to improve it.
- High water retention that keeps the moisture long enough for the roots to absorb it in the dog days of the summer.
- Clay soil is often packed with nutrients. That’s because clay particles are negatively charged, they attract positively charged elements such as magnesium, potassium, and calcium.
- Clay is a fertile ground for good bacteria that break down organic materials in the soil for the roots of the plants.
- Clayish soil is easier to improve and maintain than sandy soil.
- Clay soil is more suitable for top-heavy trees since it provides more support to the roots.
- It drains slowly, which is the main cause of root rot for many plants.
- It freezes over in frigid conditions and stays frozen for longer than other soil types.
- Clay soil is often alkaline, and that makes it less than suitable for most of the plant species that you can grow in the garden.
- The dense horizontal layers or clay particles are easy to compact. Compact soil is poorly aerated and makes it harder for the roots to penetrate and spread out.
- When the moist clay particles freeze in the winter, they expand and lift up, which is known as soil heaving.
How to Improve Clay Soil
Now that we know what’s wrong with clayish soil, we can pick the right strategies to amend it and make it more plant-friendly. There are a few ways that you can go about improving your clayish soil. However, you need to be both consistent and patient. You won’t see the results straight away, but with persistence, you can turn your plant-free garden around. Here are a few strategies to follow.
Change Land Topography
This ambitious strategy is not as hard as it sounds. You’re not going to build hills and valleys in your clayish garden. Rather, you’ll be creating raised beds, terraces, berms, and shallow trenches or permaculture swales. The idea is to change the contours of the land to speed up the drainage in the high points and oxygenate the water in the low areas. The best time to change the physical features of the clay soil surface is in the summer when the soil is dry.
Aerate the Soil
As we have seen, heavy soil is poorly aerated thanks to the dense and tightly arranged clay particles. So to change that, you’ll need a digging fork or a plug coring aerator. Either of those two pieces of equipment will break up the compact sheets of soil, oxygenate the soil to encourage the growth of good bacteria, and improve drainage. The best time to aerate the soil is in the spring and fall each year. Always work backward and dig deep holes in the soil from one end of the garden to the other.
Amend Clay Soil
While the above strategies work on changing the structure and tilth of the clay soil, amending the texture of the soil can bring the change you need in a much faster way. The idea is simple enough. You need to introduce new materials to the clayish soil to balance out the clay particles. Here are a few recommended amendments.
- Leaf Mold: You’ll need to age your leaves for at least a couple of years before they turn into crumbly and nutritious material. They are packed with organic nutrients, and when worked into clay soil, they improve its drainage and texture.
- Worm Castings: Worm castings are an excellent material to loosen up the compact clay soil and infuse much-needed microorganisms there to make the soil more fertile. However, you’ll need great quantities of the stuff to bring about any noticeable change to the clayish garden. We recommend you use this along with other materials such as leaf mold.
- Green Manure: Some plants are grown specifically for the sole purpose of cutting them and spreading them all over the clay soil to amend it and inject it with nutrients. Some recommended plants of this type include clover, alfalfa, lupine, cowpea, mustard, radish, vetch, sunn hemp, and soybean. You can plow the cut plants or leave them to rot on the surface of the garden.
- Cattle Manure: Add as much fresh manure as you like. It changes the texture of the clay soil and enriches it with nitrogen and minerals. However, only use the manure of cattle and other livestock that are fed with organic food. That way, you’ll avoid adding herbicides to the soil, which could end up in the veggies you grow and eat.
You should apply any or all of the above amendments to already tilled soil. After you irrigate the soil, the added materials will blend in and become part of the garden soil.
Clay Soil Maintenance
Even with the above amendments strategies, there’s no guarantee that your clay soil will not revert back to its clumpy and poorly aerated old self. So you need to apply a long-term strategy of care and maintenance to make the changes more long-lasting and permanent.
Compost of all its varieties and types is by far the best material you can add to the clay soil to maintain its stability and texture in the long run. Since its nutrients are readily available to the plants, it doesn’t need breaking down. In other words, carbon, nitrogen, and the humic matter will have an immediate impact on the texture and structure of the clay soil. To avoid high concentrations of compost lying on top of the solid sheets of clay, you should break the layers of clay first. Add about 2-inch layers of compost and work them into the tilled soil. Keep repeating that digging deeper into the soil as you go. After breaking about 10 inches of clay, you will notice a change in the soil texture and tilth.
Use cover crops as a solid way to introduce organic material to the stubborn and dense soil. Any time the garden is taken a rest between crops, you should plant cover crops. Notable Leguminous cover crops that work well with clay soil include beans, lentils, alfalfa, velvet beans, and lupine. They fix the nitrogen in the soil, and the plants themselves turn into green manure after you cut them and plow them into the soil.
Do Not Disturb Clay Soil
One of the key warnings that agriculturalists keep sounding is that you shouldn’t disturb clayish soil. Don’t walk around the tilled soil unless you have to. When digging holes to aerate the soil, do that in a backward direction so as not to step on the holes you just created. Clay soil has a tendency to compact under pressure. So avoid using heavy machinery in the garden, especially when the soil is moist. That way, you’ll avoid unnecessary and excessive tillage, which tends to diminish the organic materials and nutrients in the garden.