How to Improve Clay Soil

Good garden soil is typically a good mix of clay, sand, organic material, and mineral particles. Heavy clay soil, on the other hand, does not have a good mix of these materials and can be very difficult to deal with as a gardener.

While some trees and shrubs can do very well with dense soil varieties, most vegetables and flowers cannot thrive, or often even survive, in these difficult growing conditions.

Our first garden bed on our current property was a challenge to start. The soil was very dense, very nutrient deficient, and very slow draining. We even considered raised beds at one point as our main garden instead of in the ground.

But, even though we struggled with clay soil for the first couple of years, it can be improved.

What is clay soil?

Unlike good garden soil, clay soil is composed of tiny, very fine soil particles that compact and have the tendency to become a hard, solid mass that doesn’t drain well and is incredibly difficult to work with.

This soil type is pretty common across the United States, so if you live in the states, you’re probably dealing with it. One sure fire way to know you are, though, is when you see water puddling on top of the dirt or really struggle digging into the soil.

But, on that note, there are actually several types of clay soil and you can’t really know which type you have without performing a soil test. This test can be incredibly beneficial when working towards improving your soil and knowing exactly what your garden produce will need to thrive.

Advantages of Clay Soil

Clay soils do have a few advantages, believe it or not. One of the top advantages is the fact that these soils hold on to nutrients and are typically very fertile.

Another is they hold on to moisture very well, which can be beneficial when you’re struggling with the ground drying out too quickly.

These soils are also great at helping trees, shrubs and a few other perennials and annuals establish strong root systems and stay insulated from temperature extremes. The high density of the soil results in very little heaving (pushing plants out of the ground) which makes it easier for them to stay put.

Overall, clay soil gives you the advantage of less watering, higher nutrient density, and a place to establish strong roots. Not sounding so bad now, huh?

Disadvantages of Clay Soil

Of course, there are disadvantages to clay soil. These seem to be what most of us gardeners focus on the most.

It can be very difficult to break the soil to shovel or till. It compacts very easily which makes both of these tasks difficult to accomplish.

Since this soil type retains moisture, which has its advantages, it becomes sticky. Many times I’ve wound up with mud caked to my boots trying to walk out in the garden after heavy rain.

This type of soil has all the properties it needs to hold on to all of the nutrients you want, but it also holds onto things you don’t want, like salts. The density of the soil mixed with high salt levels can make it very difficult to alter the pH of your soil.

Improving Clay Soil

It doesn’t take a lot to make clay soil into amazing garden soil where your crops can flourish. The more of these steps you take, the more incredible your soil will be.

Improve the Entire Bed At Once

I’ve heard of people saying that they only amend each hole they dig to plant in. Well, that works in theory. You add the soil/compost mixture once you backfill. But, the roots of the plant you just planted are going to have an incredibly difficult time breaking through the clay that surrounds them. 

That being said, it is best to prepare your garden bed and begin improving it all at one time. So, pick your spot and get started so we don’t have a bunch of root-bound plants in a month or two. 

Tilling & Aerating

Aerating your clay soil is essential to break it up and improve drainage. We aerate our soil twice a year. We till in organic matter in the fall with a rototiller and simply use a broad fork to poke holes and move the soil a little in the spring before adding more well-aged compost to the top and planting. 

There is a strong pull to no-till gardening and it can be incredibly beneficial. Over-tilling is a concern and can lead to further compaction and more problems than any gardener wants. But, we do gently till every fall. If you don’t want to till it, you don’t have to. Simply take a broad fork or similar tool to poke holes and then add your organic material on top. It will work itself over time through the aeration holes you created. 

Organic Material

Adding organic material to any garden is essential to soil health, but it significantly improves clay soil almost immediately. I’m always amazed when we throw a nice, thick layer of compost over the compacted soil we always begin with how different the composition is when we are finished. It’s workable, well-drained, nice, loamy soil that I can dig into with my hands and not feel like I need a chainsaw to break the surface. 

Organic material needs to be added in copious amounts in the beginning. Around 6″ of material should be added as soon as the soil is aerated so it can wash down into the newly created holes and work its magic to soften the soil. 

The following organic materials all work really well to help improve your soil. 

Compost

Your own compost is a fantastic addition to improve clay soil. Make sure it is well-aged and if you composted it yourself… even better. If you’re applying composted manure, it is essential that you ask questions and insure that the animal never ate anything that was sprayed. If the hay they consumed was sprayed, don’t put it in your garden. You’re just asking for headaches and dead plants. 

Manure

You can put manure directly on your garden bed and allow it to work into the soil as long as you have at least 3 months before you are planting anything. The same thing, you’ll want to make sure that the animal never consumed anything that was sprayed. Or… well, you’ll probably end up with a lackluster gardening season. 

Make sure that the soil isn’t drenched when applying manure and make sure there isn’t any heavy rain in the forecast. This helps decrease runoff so that the nutrients say in your soil and out of waterways and other places we don’t want the manure to wind up. 

Worm Castings 

Worms are pretty amazing and their castings are a great addition to your garden. They are high in minerals and nitrogen and the richest fertilizer we are aware of. You can create your own with vermicomposting, or you can purchase them in bags. 

Leaf Mold

If you’ve never heard of leaf mold, you aren’t alone. I had never heard the term used until a couple of years ago. What it is is leaves that have been left to decompose over a few years time. The result is some amazing black gold for you to add to your garden. 

We actually picked up several tons of leaf mold this year because we certainly didn’t have enough compost to add on our own and I’m leery of adding compost from elsewhere. This stuff worked amazingly well and transformed our expansion into workable, beautiful, loamy soil in a matter of the couple of hours it took to put it on. 

Utilize A Cover Crop

Cover crops are great to help amend your clay soil. They’re pretty simple to utilize, too. You generally just spread them down like you’re planting grass and wait. 

Cover crops work to enrich your soil by helping incorporate the amendments you add when they’re rooting in. They also help add nutrients and prevent weeds and erosion. There are several crops to choose from, depending on your climate and what you’re looking for. 

Adding cover crops in the fall is what most typically do, but you can add summer cover crops, especially in bare places, as well. We planted a cover crop and were amazed at how much healthier our soil was afterward. They really do an amazing job at improving soil structure. 

Mulch

If you’re not going to put down a cover crop, you should add a good layer of mulch to help improve the soil and protect it from erosion. Leaving the soil bare will just cause it to compact again. There are lots of different materials you can utilize to mulch your garden. And in the fall some are completely free.

Shredded leaves make an amazing mulch for your garden, so if you have some, add some. They work just the same way in the forest as they will for your garden. To shred them, simply run them over with a lawn mower. 

Straw is another great mulch and is our go-to because we don’t have a ton of leaves available (yet). However, use straw with caution. You need to make sure it hasn’t been sprayed (just like the food the livestock ate). A lot of grass crops are sprayed now and they will wreak havoc on your garden. So, the moral of the story is… know your farmer and ask questions. 

You’ll want to mulch lightly before the wet conditions of winter but a little heavier if it’s dry and hot. 

What Not to Do

Now you know what to do. However, there are some things you’re going to want to avoid. I’ve laid them out for you here. 

Walk On It

I find it best to make permanent pathways in your garden. This helps avoid walking in areas you should be planting plants. To make permanent pathways, you’ll want to select the paths of least resistance knowing full well that everyone is going to take the short distance whether it’s where your intended path is or not. You can line them with stone, lay mulch down, or do whatever you need to do. 

Walking in the garden will quickly compact it back into the compacted clay that you just spent all of that time improving. So, lay out some paths and try not to make your planting beds too large (2-3 feet wide) so you can reach all the way. 

Add Sand

There is a common misconception that adding sand to clay soil will improve it. This will not work. Instead of improving it, you’ll probably wind up with a bed of concrete-like material. Worms won’t be able to live in it and neither will any plant life. So, steer clear of the sand and utilize some of the additions I mentioned above. 

Improving hard clay soil will pay off in multiple ways when you’re able to pick that fresh produce straight out of the garden and place it on your dinner plate. The feeling of pride it gives, the sense of accomplishment… it makes it all worthwhile.

Each year you’ll want to aerate, add a fresh layer of organic material and add some mulch, but every year it will get easier and easier and seem like it requires less and less work. 

Other Posts You’ll Love:

• How to Start an Organic Vegetable Garden
• Protect Your Soil With Cover Crops

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