How to Fix Heavy Clay in Your Garden: Easy Tips

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As home gardeners, we often don’t get to choose our soil. Every time I have moved, I have always had clay. The worst of which is located on my current home site. I’m talking good luck with a shovel you might as well get out the pick-axe type clay. The kind that makes your back sore. I answered the question of how to fix the heavy clay soil in my garden by looking at the forested portion of my property. When I began fixing the clay soil nature’s way, I finally began to see a huge difference.

closeup of clumped together clay soil with red pea seeds planted and string lines

Determining your Soil Type and Soil Structure

The main types of soil found in home gardens are made up of either sand, clay, silt, or a combination of these three called loam. Sand, silt, and clay are identified by the size of their soil particles. The first step in improving any soil is understanding what type of soil you have.

Clay Soils

Clay soils or heavy soils have the smallest soil particles. Because of this, they can potentially hold nutrients better than sand or silt. Clay soils also drain very slowly because they become so densely packed together. Wet clay soils are very slippery and sticky. Dry clay soil often cracks and gets very hard. Hard clay is almost impossible to dig through with a shovel. Clay soil is easily compacted. Plant roots may have a hard time penetrating compacted clay soils and may develop shallow root systems that require more watering.

Funny (or sad) story: The clay at my house was so compacted that when we rented a 3,000 lb. trench compactor to compact an area for a concrete slab, the soil level did not change an inch! Hence the pick-axe reference above!

Sandy Soils

Sandy soil or light soils have larger particles and drain very quickly and are easy to cultivate. Think of your kid’s sandbox. It’s pretty easy to push a shovel into the sand. Sandy soils are usually low in plant nutrients which get washed out with rain. Sandy soils can also be very acid.

Silt Soils

Silt soils have intermediate sized soil particles. These soils are often fertile, hold water better than sandy soils, but are easily compacted.

Loam Soils

Loamy soils are a mixture of clay, sand, and silt. Count yourself lucky if you have loam soil in your home garden! Loam soils are fertile, well-drained, have good tilth, and are easily worked.

The Jar Test

One free way to determine how much clay, sand, or silt you have in your soil is to do what is commonly called “The Jar Test”.

  1. Grab a quart or pint-sized mason jar and a water-tight lid.
  2. Fill the jar 1/3 full of the soil to be tested. Make sure to remove any debris like rocks or leaves, sticks, or roots.
  3. Fill the rest of the jar with clean water. Leave a little bit of space at the top.
  4. Put the lid on the jar and shake it! You want to shake it up until it forms a uniform slurry.
  5. Set the jar on a level surface and wait for 1 minute.
  6. Place a mark on the outside of the jar, showing the coarse sand layer settled at the bottom.
  7. Leave the jar on the level spot for 2 hours.
  8. Mark the top of the next settled layer. This is the silt layer.
  9. Leave the jar in the same spot for 48 hours.
  10. Mark the top of the next settled layer. This is the clay layer.
  11. Use a ruler to measure and record the height of each layer and the total height of all three layers.
  12. You can now calculate the percentage of clay, silt, and sand in your soil.

Get a Soil Test

Getting a professional soil test is a great way to understand your soil on a deep level. I highly recommend soil testing. There are many different options for soil testing. In the United States, you can contact your local county extension service and ask about soil testing options in your area.

Another great option that I used myself is this soil test kit by Redmond Agriculture. They make it so easy. The kit comes to you in the mail with clear instructions on gathering your sample and mailing it back to them. In short order you have all your results emailed to you. It’s a great program that really helped me identify some problems with nitrogen in my garden. The chart below is from the first soil test I took before I tried to address the heavy clay soil in my garden.

As you can see from the chart above, my garden soil had pretty good levels of nutrients, and the PH was in an optimal range, but the soil was very low in nitrogen. This really helped me understand why my garden plants were just not thriving like I thought they should. It wasn’t some failing on my part, it was the soil!

My Light-Bulb Moment: How the Forest Produces Productive Soil

My house sits on 5 acres. Three of those acres are the yard, garden, and an old, abused hay field. The other 2 acres are forest. After several years of adding small amounts of compost, leaves, and grass clippings and tilling them in each spring, the clay soil in my garden was not improving much. It was frustrating.

I had learned about adding calcium sulfate to clay soil to loosen those tiny clay particles and improve structure, but I just wasn’t sold on that idea. There had to be a better way.

closeup of heavy clay soil clumped together in a row of planted potatoes

One afternoon, I was taking a walk through the forested portion of our property, and I realized that only 200 yards away from my vegetable garden, in the forest, there were the most productive, beautiful, fertile soils. My little 2 acres of forest supports 9 different commercial tree species! I realized that I had been going about it all wrong in my garden and I needed to mimic nature. The forest does not till.

closeup of a small grand fir tree with a thick mulch of pine needles and branches on the ground

So how does the forest have such productive soil only a few hundred yards away? The secret is organic matter and lots of it. Leaves, pine needles, branches, grasses, and plant matter all fall to the soil surface every year and decompose. These yearly soil amendments sit on top of the soil. This feeds the soil microbes underneath who then break down this organic matter into beautiful soil. In my garden space, I had been disturbing those microbes every year by tilling. I was trying to take nutrients from the soil without adding enough back in.

How to Fix Clay Soil: Nature’s Way

Organic Matter and No Tilling

The last few years, I have added truckloads of compost, leaves, and grass clippings to my garden. I have spread these soil amendments evenly across my garden and then planted my seeds each spring. No tilling. The results have been astounding in the best way. My heavy soil has become productive!

closeup of a watermelon growing on a vine next to a corn stalk with a thick layer of composted wood chips on the ground

The thick layer of compost and leaves has cut the number of weeds to 1/3 of what I used to have. I spend very little time weeding. I also almost never have to water my garden. The leaves hold the moisture so well, I only water in August when temperatures reach the 90’s.

When to add Leaves and How to Plant Seeds

A friend who lives in town gives me truckloads of bagged leaves every fall and I simply dump and scatter those leaves in my garden as I’m putting it to bed for the winter. The leaves start to break down over the winter months and feed the soil with fresh nutrients. They also serve to cover the soil and protect it from the elements during that time.

The following spring, I simply pull back the leaf mulch, plant my seeds in the soil below, wait for them to germinate, and then pull the leaves back around the plants. I then add a thick layer of compost to the entire garden area. If the area is particularly weedy, I put down a layer of unbleached paper under the compost before I plant my seeds. This has also really cut down on the weeds over time.

I don’t have enough raw material to produce enough compost for my large garden at home, so I don’t have a compost pile. My local garden store has bulk compost that they will load into the back of your truck with a tractor. It is mostly composted wood chips and animal waste from a local agricultural research university and is certified herbicide free which is important when buying compost for your garden.

All my plants have been more productive since switching to this method. The yields on all my vegetable crops have increased noticeably. The results didn’t take a long time to notice either. The first year I started using these methods I saw noticeable improvement. The answer on how to fix clay soil was right there in front of me on my own property. I just had to open my eyes and look around.

rows of small green tomato plants growing up through a thick mulch of leaves and pine needles

The Takeaways on How to Fix Clay Soil

Stop Tilling

The forest does not till! Tilling destroys soil structure and disturbs beneficial microbes. Tilled soil also gives room for weeds to grow. Let the earthworms mix your soil for you. If you apply a thick enough layer of compost on top of your soil in the spring, you can plant your seed directly into the compost without needing to break up the soil. I did this last year with my corn seeds and had the best corn crop ever.

Add Organic Matter

Any and all organic matter is going to help your garden. Just don’t do too much of any one kind. As long as you can pull the mulch back to plant the seeds in soil you can’t add too much organic matter. Layering compost, grass clippings, straw, leaves, leave mold, coffee grounds, or rotted manure on top of your soil will create a rich soil that will provide all the nutrients your plants need. Both water holding capacity and water movement will improve. An added benefit of organic matter is that it attracts worms!

Benefits of Earthworms in Clay Soil

Earthworms improve soil by breaking up the clay soil, creating air pockets, encouraging beneficial bacteria, and adding nutrients. The best way to attract worms to your garden is to keep the soil moist and add large amounts of organic matter. Worms don’t like overly wet soils, but they love good garden soil. Attracting more worms to your garden is always a good idea.

Tell me about fixing your clay soil!

Drop a comment below and share your clay soil story. What have you done to improve your soil? Are you just starting new garden beds and wondering if these techniques will work for you? Have you tried any of these tips and seen results? I would love to hear from you.

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Other Tips How to Fix Clay Soil

Check out these other posts about improving clay soil!

How to get grass seed to grow on hard packed dirt

Clay Soil Drainage Systems: How to Fix Waterlogged Soil

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closeup of clumped clay soil on top of image and a tree growing in a forest on the bottom of image with the words, "How to fix heavy clay soil look to the forest"

3 Comments

  1. Fantastic! Just what I needed to learn for our clay garden. Thanks! Do you think laying a layer of cardboard overtop of the clay would help with the tougher weeds? My worry is I will just make the soil better for our weed patch. Thanks.

    1. Hi Trina! I haven’t tried cardboard myself, but I have used unbleached paper. I bought a big roll of thick brown paper from amazon a few years ago and in weedy areas, I do lay down that paper before I put down compost. I’ll update the post with this info! Thanks for being here!

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