Clay soil is soil that gets comprised of excellent mineral particles and not much organic material. The resulting soil is quite sticky. Since there is not much space between the mineral particles, it does not drain well.
When you wrestle with heavy, compacted clay in your lawn and garden, your body and your plants can show the strain. But do not despair. Clay soil offers many benefits, but it can need a hand to reach its potential. Healthy, well-maintained clay soil translates to less work for you and less stress on your lawn and garden. With these insights and a little effort, you can fix your heavy clay soil and reap its rewards:
Nutrient Retention
The denseness of clay soil makes it great for storing nutrients. Other soils such as sand will allow nutrients to leach away. Clay soil holds onto applied fertilizers and organic matter. It results in improved nutrition for plants. The reason for this is that the particles that makeup clay soil get negatively charged. Meaning they attract and hold positively charged particles, such as calcium, potassium, and magnesium.
Moisture Retention
Clay soil is dense and compact. This attribute makes it hold water better than sandy soil. As a result, water does not flow away as quickly, and some plants can benefit from moisture retention.
Less fertilizer
Clay soil is rich in a variety of minerals and nutrients that are beneficial to the growth of plants. Clay will often contain calcium, potassium, and iron in their natural forms. In addition to the genuine mineral content, the soils’ ability to store elements can need less fertilizer.
Physical Plant Support
Clay soil provides a density that enables plants to stand stronger. Other soil types, like sand that have a looser texture, do not offer the stability of clay and can allow plants to keel over and collapse due to lack of support.
Disadvantages of Clay Soil.
Poor Drainage
Because of the lack of air pockets, clay restricts water movement and drainage. Clay gets commonly used to line the bottom of holding ponds for this reason. However, this water retention can drown plants and rot roots during times of rain. This poor drainage can also result in shallow moisture that is susceptible to evaporation.
Hinder Root Growth
In addition to poor drainage, this dense clay structure will also hinder root growth. It is not uncommon for plants growing in heavy clay soil to never grow outside of the hole they were initially being planted in—stunting their growth both below the ground and above. As a result, they become root-bound, just like plants growing in a container pot. In addition, because the roots have a hard time penetrating the clay, plants will likely have shallow roots and need to get watered more frequently.
Hard to work
When clay soil is wet, it becomes a heavy, sloppy mess that sticks to tools and your shoes. It becomes challenging when it dries out and sometimes feels like you are breaking up concrete when you try to work it. If that wasn’t enough, the fine soil particles could become airborne when clay dries out, creating dust that settles just about everywhere.
Amplifies any negative soil conditions
Clay soil is very good at storing soil elements, both good and bad. For example, if your soil tends to be acidic, then the clay will amplify the problem. The same is true for areas with higher levels of alkalinity. On the other hand, clay soil is also very good at collecting and storing destructive salts and salinity, destroying your plants.
Lacking beneficial bacteria, microorganisms, and organic matter
Heavy clay soil usually lacks healthy soil bacteria, microorganisms, and worms—the things that help plants grow and flourish.
Yard drainage problems can wreak havoc on a garden or lawn, especially after heavy rain.
Improving Clay soil drainage:
Aerate Clay Soil
Injecting air pockets into clay soil is essential for improving drainage, breaking up compaction, and inviting soil microorganisms. When clay soil gets appropriately prepared, one can find a sheet of clay underneath a layer of loosened/amended soil.
Here are three tools that get used for this work:
- Broadfork
- Digging fork
- Plug coring aerator
Use your tool of choice to aerate garden soil twice a year — in the fall as the season ends and in the spring before planting. Fall aeration is vital because it counters any acts of gravity/compaction throughout the season.
To use these tools, simply start at one end of the garden and work backward (so you do not step on loosened soil), poking holes throughout as deep as you can.
Or let clay-busting plants do the work for you.
A Note on Tilling: Are you wondering about tilling to improve clay soil? In many cases, tilling can contribute to more compaction.
However, as long as the soil is moist (but not waterlogged), a one-time tilling can be a decent aerator.
Add Soil Amendments to Clay Soil
Add soil amendments immediately following aeration so that the rain can wash them into the holes and soften the clay. You’ll need lots of organic matter at first to change the structure of the soil.
The following types of organic matter attract microorganisms that speed up soil improvement.
Compost
Homemade compost is an excellent soil conditioner that improves drainage. Place the compost on the flower bed that you want to improve the soil of and dig it in with either a shovel or a tiller. Make sure you work in some of the existing soil into the compost, as it will help any flowers you plant acclimate to the surrounding soil both on the side and below the bed.
If you have more time (and you want to do less work), you can simply lay the compost on top of the soil and let it sit for a season or two.
It works best to place the compost on the clay soil early in fall and let it sit through to spring. The compost will work its way into the top few inches (8 cm.) of the clay and will give your bed a good start.
Green manure
Cut green plant matter from other garden areas and spread it evenly over the soil for a nutrient-rich amendment. You can use herbs of all kinds, but comfrey is ideal. Herbal compost teas can also get used.
Livestock Manures
All kinds of garden-approved, composted manures are excellent soil conditioners. The only modern challenge is the potential for it to get contaminated with herbicide. Learn more about herbicides in manure.
A Note on Manure Application Etiquette: Do not spread manure on frozen or waterlogged soil before heavy rain. It will help to keep your local waterways clean and ensure valuable nutrients don’t wash away.
Worm Castings
It is one of my favorite homemade sources of organic matter, which is high in minerals, nitrogen, and humus.
Leaf Mold.
Leaves that have decomposed for a year or two are considered leaf mold, a rich and crumbly “black gold” for garden soil.
Herringbone Drainage
This system gets constructed by creating smaller parallel trenches in your yard that run to an enormous trench that carries water away to a soakaway. The smaller trenches get filled with gravel, and the large canal has a drainage pipe that allows it to move the water without hitting your soil. Your soakaway can be just dug into the soil for dispersion or lined with concrete for retention.
- Start by digging the main drainage trench—two to three feet deep in a straight line across your garden. Be mindful of the slopes of your garden when positioning the canal ground ditch. You want to have the canal at a downward slope.
- Dig trenches that will feed into the main channel in a herringbone fashion.
- Cover the surface of the trenches with gravel or small stones.
- Lay piping in each trench and interconnect them. Use special drainage piping with drainage holes across the top to collect the water.
- Angle the pipes so that water will flow into the main pipe.
- Build a soakaway—a deep, circular hole with sloping sides—at the end of the main pipe. The soakaway should be at least 6 feet deep and filled with rubble to collect the water.
- Position it well away from the house.
- Cover your soakaway with thick plastic sheeting.
- In areas of poor rainfall, you may want to build a concrete soakaway to store water for gardening during drier times.
French Drain
A cousin of the herringbone drainage, the french drain is a little less complicated to construct. Instead of multiple trenches, you need only one, with gravel and along drainage pipe. This system is a little more complex as you need specific ratios and angles for it to work at its best. It can shoot water to a soakaway or just away from home.
Underground Drain Pipe
The most straightforward system of them all, an underground drainage pipe, is just what it sounds like: a pipe designed and installed to allow water to pour down it and away. These take water from the lowest point of your yard and disperse it accordingly.
Plant a Cover Crop
Cover crops help incorporate soil amendments deeper into clay soil by rooting thickly and downward. As a result, they reduce erosion and enrich the soil. You can plant either fall or summer cover crops.
There are a lot of cover crops to choose from, and which is right for you will depend on your climate. For example, cold winter temperatures kill some cover crops so that you can plant in the spring without a lot of prep work. Other cover crops require tilling or cutting before planting crops.
Plant fall cover crops in late summer or early fall. They’ll provide overwintering habitat for beneficial insects.
Plant summer cover crops in late spring. They’ll fill empty spaces in the garden and provide flowers for pollinators.
Chop cover crops back about three weeks before planting if they haven’t died back on their own. Then, a few days after cutting, use one of the aerating tools mentioned above to poke holes into the root mass to incorporate some of the plant matter.
Soakaway
Think of a soakaway as a garden wall that acts in reverse; instead of retaining water, this installation will remove excess levels of hydration from the perimeter of your property. Digging a soakaway will allow rainwater to gradually seep into the ground rather than remaining on the surface, where it will slowly begin to redistribute itself into the soil before it can become polluted. It not only helps your garden turf last much longer, but it’s also one of the most environmentally-friendly solutions available to heavy rainfall.
Gypsum for Clay Soil
Gypsum is another name for calcium sulfate, a substance that sometimes gets recommended as a soil amendment for clay soils. This chemical compound disperses the high levels of sodium present in some clay soils, which makes the soil more permeable to water. So if your soil develops a white crust when it’s dry, it may be high in sodium.
Apply gypsum to your soil when the surface has dried out somewhat and is workable with a garden fork. Spread 1 pound of gypsum per 5 square feet and lightly mix it into the top 2 or 3 inches of soil. Rainfall and irrigation gradually wash gypsum out of the ground, so the effects are temporary. Supplement gypsum applications with other methods of cultural management to improve drainage in clay soil.