How To Till Clay Soil: A Complete Guide

Soil isn’t as simple as it seems. It’s a combination rich with sand, organic matter, moisture, and minerals. Keeping these elements in check guarantees you healthy soil that you can cultivate.

Working with clay soil isn’t very enjoyable, but it is possible. It’s not the easiest to cultivate, but using a tiller and some patience, you can reap its benefits.

What Is Clay Soil?

To define clay soil, we need to take a step back first and take a look at what soil is composed of. 

Soil is a combination of water, organic matter, mineral particles, and air. These mineral particles come from dissolved rock matter, and their relative size determines the type and texture of the soil. The ideal soil texture is called loam – a soil texture with 20% to 40% clay, and the rest made of sand, silt, and a heavy dose of organic material. 

The size of soil particles determines the texture of the soil. We’ve got sand, silt, and clay. A soil mostly made of sand is labelled as sandy, where the particles are relatively big and allow proper drainage.

On the other end of the spectrum, you’ve got clay soil.

Clay is the smallest of the three soil particles, with particles a minute 0.002-millimeter in diameter that you can’t see with the naked eye. Because of their tiny size, clay particles have almost no spacing in between them, leading to the formation of sticky soil that doesn’t drain well.

Here are some of the characteristics of clay soil:

  • Heavy to dig in
  • Holds water well
  • Slow drainage after rain
  • Warms up slowly in summer
  • Cracks like a brick when it dries up

How to Check if You Have Clay Soil

You probably already know whether you have clay soil or not.

Does your soil crack up like bricks when it dries? Does it clog? Do you find it sticky and soggy when you step in it? 

If the answer to these questions is yes, then you have soil that is packed with clay. 

Another way to test for clay-based soil is to rub a piece of it between your fingers. It’ll feel smooth and not gritty. You can also shape a scoop of clay soil into a ball without it crumbling. 

How to Improve Clay Soil

When improving clay soil, the goal is to work on the soil’s texture. We need to introduce coarse matter that can go deeper between the fine clay particles, creating space for water to drain and for air to circulate. 

Adding Sand to Clay Soil

You would need large amounts of sand and silt to dilute the effect of clay in the soil. This solution is intuitive, but it’s not necessarily the most practical. First, you need huge volumes of sand to balance the clay (460 lbs per sq yd in case of 40% clay soil). Second, adding that much grit to clay might make the soil unstable. 

Sand is expected to add volume to the soil. You should consider this if you’re working on a bed of a specific size. In this case, you might need to remove some of the clay before you start.

When you add sand to clay soil, the soil should be wet enough that it’s moist, but not soggy.

You can try this in relatively small areas or flower beds and see how it works for you. If you need to add sand to bigger areas, the best way is to do it is with a garden tiller, where you need to work it into eight to 12 inches of soil.

In heavy soil – that is, soil made up of more than 40% clay – adding sand will be more tiresome. You can certainly try it, but we recommend adding something more practical, like compost.

Adding Compost to Clay Soil

Adding compost is an excellent way to improve the texture of clay soil, where it helps in the formation of crumbs. Crumbs are structures in which the soil particles combine to form round shapes. Proper crumb formation allows for root development and good aeration and drainage. 

Compost also boosts the soil’s fertility and tilth, which is the condition of the soil. You do want your soil to be rich in compost. If you already have your compost pile, that’s great. If not, we recommend you use dry shredded leaves.

Collect as many shredded brown leaves as you can from now on. We’ll be using these as compost!

You can add compost on its own or combine it with sand if you want to. The important thing to keep in mind is that compost is different from mulch. While compost is great for growing flowers and vegetation and retaining moisture, it’s also the perfect medium for weed growth. So, you need to pay attention to that.

Adding a mulch of shredded leaves or grass clippings would be a clever solution to this situation. Besides, it decomposes over time, which improves the overall soil tilth. 

Using a Tiller in Clay Soil

To get sand and compost deep into clay soil, manual digging won’t be efficient. Not to mention that digging clay soil is a challenge in and of itself. You need to use a tiller to treat clay soil, and here’s how. 

Test the Soil Moisture

You don’t want to till soggy soil because this will result in clumpy bits, which won’t help in seed sowing. That’s why you should test the soil moisture first. Wait for the soil to be dry, scoop a handful of the soil by your hand, and try to shape it into a ball. If the ball shape holds, then it’s too wet to till. 

In this case, you need to wait for a couple of days for the soil to dry, then test moisture again. The ball shouldn’t be holding as it did. You can try a simple squeeze, and if it crumbles, then you can till.  

On the contrary, having super-dried clay soil isn’t preferable either. In this case, you’ll find the soil too dry that it might crack. If you find yourself in this situation, you need to water the soil and then wait for a couple of days to dry, so that it’s not “brick dry.”

Till with Several Shallow Passes

Clay soil doesn’t like deep aggressive tilling. The key to tilling clay soil well is to make several shallow passes over the same area so that you don’t overwork your tiller. 

Start with the shallowest setting on your tiller and work on your first pass. Then, add two inches of depth and work in a perpendicular direction. Keep on increasing depth gradually and changing direction till you get to your desired depth. 

Add Organic Matter for Better Drainage

As we discussed, the main reason for the improper drainage in clay soil is the superfine texture of clay particles. So, what can we do to improve drainage? Introduce coarse texture through organic matter.

You’ve got multiple options here; partially rotten leaves, compost, or even pine needles. To introduce the organic matter, spread it at a depth of three to four inches into your tilled bed, then rototill into a deeper depth of seven to eight inches.

Doing this once a year should yield good results and improve the soil’s overall performance and texture. 


While tilling and adding amendments can help to improve clay soil, they won’t be effective unless you ensure you’ve got ongoing maintenance to your soil. 

Choosing when to till amendments into clay soil is critical. An ideal approach is to till in autumn, giving an opportunity for soil microbes to grow over winter. This, in turn, prepares for the soil to dry out well in spring. 

Spring is an excellent opportunity to rototill your soil to improve drainage and aeration throughout summer and incorporate amendments even deeper into the soil. 

How to Test If Your Soil Is Healthy

The most straightforward test for healthy soil is the ‘crumbling ball’ test we mentioned earlier. Grab a scoop of your soil and try to shape it into a ball.

If it forms a perfect ball that doesn’t crumble, it’s clay soil that needs some amendments. If it can’t form a ball, then it’s probably too sandy.

Finally, if it forms a ball that crumbles easily, then congratulations, your soil is healthy! 


Clay soil isn’t the easiest to deal with at first, but once you know how to improve its texture, you can work wonders with it.

To conclude, we’d say that introducing sand and compost through frequent shallow tilling is key to maintaining clay soil.