Clay soil is usually poorly aerated. Some grass types such as tall fescue grow well in clay soil, but some may struggle because of poor drainage. Most grass types require well-aerated soil to grow faster and healthy. So, how do you improve the drainage of clay soil?
The best way to improve clay soil for your lawn is to mix and till with compost, gypsum, or pine bark. These clay soil amendments will help loosen up the structure of clay soil and improve porosity, aeration, and drainage. Another option is to aerate the lawn with a plug aerator every spring to improve aeration.
Be it St. Augustine grass, bermudagrass or any other grass type, you may want to amend a yard that has clay soil before laying down your sod or seed. Some simple steps can help aerate the soil, and that’s what I’m going to show you.
How to know your lawn has clay soil?
Clay soils have fine particles that define their structure and texture. This kind of soil aerates poorly and as such will hold a lot of water and remain wet and cold throughout winter and dry out in summer.
To test for clay soil in your yard:
- Dig up a sample in your yard and scoop some of it in your hand.
- Add a little water to make it damp.
- Squeeze the sample in your hand and release.
Clay soil will remain clamped in shape as opposed to loam or silt samples that would crack and break.
This test is a simple DIY one, but to get accurate results, you may want to do a professional soil test to get a comprehensive analysis that may include pH and nutrient levels.
A professional soil test will determine how much silt, clay, sand, and organic material is present in your soil mix to help you determine the right type of grass to plant in your lawn.
Why is clay soil bad for your lawn?
Clay soil is not suitable for growing a healthy lawn because the soil particles are heavy and compact easily. The soil holds too much water and can make the ground soggy or waterlogged especially if excess watering is done.
Here are the reasons why clay soil is not good for your lawn:
- Compaction: clay soils have poor drainage and can lead to waterlogging. The grass will turn yellow and start to die if there aren’t breathing spaces in the soil.
- Shallow roots: grass roots suffocate in heavy clay soil and may develop poorly.
- Soggy yard after watering: You might find yourself with a yard that’s always muddy because clay soil does not drain easily if not amended.
You can successfully establish a lawn on heavy soil but you will first need to break up the clay soil to improve drainage and aeration.
I’ve discussed below the best fixes and ways to improve clay soil and establish a lawn with healthy grass.
How to Improve Clay Soil for Lawns
To break up heavy clay soil in your lawn, you’ll depend a lot on organic material and other practices that will improve aeration and drainage. Tilling and using amendments are the best options before establishing a lawn, but even for existing lawns, there are solutions for breaking up clay soil.
Here’s how to improve clay soil for lawns:
Till and break up clay with manure
Clay soil can be hard to till especially when dry. You’ll need to soften it up a little with some water to make it damp and moist. Spread 2 inches of manure on top of the clay soil and till it in to mix properly. This will help improve drainage and texture of the soil.
Pro tip: Try not to till clay soil when wet or dry. Too much water will create a mud paddle while tilling when dry will create too much dust in your yard. Fine dust can worsen the clay soil situation because it holds too much water easily.
Add gypsum to the clay soil
Gypsum is naturally occurring calcium sulfate that you can use to break up heavily compacted clay soil in your lawn. When added to the soil, gypsum improves the texture by making the fine particles come together to make larger particles with improved drainage and aeration.
To improve clay soil using gypsum, apply 1 kilogram of gypsum per square meter of your yard and dig it well into the top 15 centimeters. Mix it well so that the soluble calcium can enhance the porosity and aggregation of the clay soils and improve air and water infiltration.
Pro tip: Clay soils are highly nutritious. If you opt to use gypsum to improve the soil for your lawn, avoid applying too much of it. Too much gypsum can eliminate essential nutrients including aluminum, manganese, and iron.
One of the best ways to improve the drainage in a clay soil lawn is by adding compost. Rotted leaves and manure are a great amendment you can add to your yard with clay soil to improve it.
Before planting new grass, add about 1-3 inches of compost onto the clay soil and till it in thoroughly to improve the texture and porosity. The organic matter in the composted leaves will also attract worms and and other microorganisms that improve the fertility of the soil in your lawn.
As the organic matter is broken down, it builds the tilth of the soil by coating the soil particles to separate them and improve aggregation. Aggregated soil is much better in terms of reduced crusting, improved water infiltration, and reduced erosion in your lawn.
Amend clay soil with humic acid
Humic acid is one of the highly recommended amendments for compacted clay soils in any yard. But how does it work? It generates and activates microbial activity that helps restructure compacted soil.
You should, however, not expect humic acid to break down clay soil that is heavily compacted. For this problem, you may want to use other organic methods such as tilling and adding compost to the soil.
Other great clay soil amendments similar to humic acid include Aerify Plus Liquid Soil Aerator and Soil Conditioner that can help break down compacted clay soil in the lawn.
Topdress with sand
A little topdressing with sand can help improve compaction in clay soils, but it is not the best fix for the problem. In fact, I wouldn’t recommend this option unless it is the only one you have available.
If you must, add a little sand to help loosen soil and open it up for better aeration. It would be an option if you’re growing grass types that grow in sandy soils. Keep in mind that this will not improve the soil structure of clay soils. Instead, opt for more organic solutions such as compost, pine barks, etc.
According to the Oregon State University, “No amount of sand can be added to clay soil to change its texture. The large sand particles provide a surface onto which the tiny clay particles adhere. The result can be a more difficult soil to manage…”
Aerate the lawn
If your lawn is too compacted because of being established on clay soil, it might be time to aerate. Lawn aeration is the process of perforating the soil by removing plugs of soil to allow air, water and nutrients to penetrate for easy access by grass roots.
You can aerate your lawn using a spike aerator or plug aerator. The tines of your aerator will poke holes or remove the plugs of soil and thatch create the needed spaces for improved aeration of clay soil.
Pro tip: plug aeration is the best way to improve the core of clay soil as opposed to spike aeration. The results will last longer because the spaces are much bigger than those of spike aeration – which are usually small from soil being pushed sideways.
Can you amend clay soil in existing lawns?
Adding compost, gypsum, and pine bark can help amend clay soil before establishing a lawn, but you might want to use other options to break down and loosen clay soil in an existing lawn.
The best way to amend clay soil in an existing lawn is by aerating and dethatching. A plug aerator can remove plugs of soil to loosen up soil and create spaces for air, water and nutrient penetration in the soil.
Allowing thatch buldup on a lawn with clay soil can worsen it because the layer of dead matter can worsen compaction and aeration problems. Therefore, dethatching is a great way to help grass thrive well on lawns built on clay soils.
What grass grows in clay soil?
If breaking up clay soil is not a working solution for you, you may want to think and opt for a turfgrass that grows in clay soil. Zoysia, bufallo grass, tall fescue and Bermuda grass are great grass types to grow on clayey turfs depending on the climate of the region.
To help your grass survive and thrive in clay soils, it is important to ensure a deeper root system that’s extensive enough to absorb nutrients and water in poorly aerated soils.