Tools and Materials
Materials
- Organic Compost and Manure
- Mulch
Rye or Clover
- Lime
- Sulfur
Product costs, availability and item numbers may vary online or by market.
What Is Clay Soil and Why Should You Amend it?
Clay soil is a type of soil that’s difficult to cultivate. Its particles are dense and tightly packed, leaving very little space for roots to grow. Drainage is an issue with clay soil. The dense structure of clay soil makes it difficult for air and water to move and makes it difficult for plants to get the nutrients they need. Amending clay soil lets you grow healthier plants by improving drainage and aeration and by allowing better root development.
The change of seasons can affect the quality of clay soil, so these are the times of year that you need to pay special attention to the soil.
Testing the Soil
If you want to amend clay soil, you’ll first need to test its condition. This is a quick and simple test that will tell you if your soil needs amending or improving.
While wearing a pair of garden gloves, grab a clump of moist soil in your hand and try to crumble it. If it doesn’t crumble but instead forms into a sticky ball like potter’s clay, it means the soil needs to be amended. If, however, the soil crumbles, then it’s in good condition and doesn’t need to be amended.
Another test you should do is to measure the soil’s pH. This can easily be done with a soil test kit. Clay soil is naturally alkaline, so the pH should fall between 6.5 and 7.5.
Other signs that your soil may need amending include yellow or dried out plant leaves or visible roots. Stunted plant growth and poor soil drainage might also indicate poor soil.
How to Amend Clay Soil and Improve Its Structure
There are many benefits to amending clay soil, including providing nutrients to plants, improving root depth and increasing the soil’s porosity. Below are various things you can do to improve the soil structure and grow healthier plants.
Aeration and Tilling
Aeration and tilling are two of the most basic methods to use to improve clay soil for lawns.
Aeration creates holes in the soil that allow water, air and nutrients to reach plant roots. You can do this by using a common garden fork or a lawn aerator.
Tilling helps break up the soil, allowing air and water to flow easily. It’s best to till when the soil is a little damp and not completely dry. Continue tilling until there are no visible soil clumps left.
Organic Matter
Adding organic matter helps improve the soil’s structure, drainage and aeration. It also helps to keep the soil at the right temperature, promoting new plant growth. Organic matter includes leaf mold, grass clippings, compost, earthworm castings, biochar and manure.
When adding manure, start by loosening the topsoil to prepare it for the manure. Incorporate the manure with a manure fork into the top 8 to 12 inches of soil. This is where most roots grow so make sure to distribute it evenly. This method works best when you add the manure in late fall, just before winter as it has a chance to decompose throughout the season.
The addition of organic matter creates aggregates of the soil particles, physically separating them and allowing for better drainage, which gives a crumbly effect. This manure can also be used as mulch.
Adding organic matter also serves as food for earthworms and beneficial soil microorganisms that convert organic matter into nutrients. This process essentially creates fertilizer for the plants.
Never use sand as an addition to the soil. It will only make it worse, as it has low water retention capacity and it will not hold any nutrients.
Raising the Beds
Another way to improve clay soil drainage is by creating a raised flower bed. Our guide, DIY Raised Garden Bed Instructions and Ideas, will give you step-by-step instructions on how to build a raised flower bed.
Once the bed is raised, fill it with properly amended soil. By creating good drainage, the water can drain out of the garden rather than puddle in the planted area.
Cover Crops
To improve the fertility of your clay soil, never leave your garden unplanted. Cover crops, like clover and rye, protect the soil from erosion, improve its structure and add organic matter.
Maintenance
To keep your clay soil performing, follow these simple tips:
- Check the density of the soil from time to time by repeating the clump test.
- Periodically check the pH of the soil by using a soil test kit. Add lime to raise the pH and sulfur to lower it.
- Consider plants with deep roots, like asters and coneflowers, that can help break up the soil further.
- To reduce air pockets in the soil, be careful not to over-compact the soil. Roots have difficulty penetrating compacted soil.
- Regularly add organic matter to maintain the improved soil structure.