If you ever need to fill a large hole in your garden or you want to level the slope of your garden, you’ll need extra soil. But without extra soil lying around, you have to get some fill dirt.
But what is fill dirt, and how do you use it?
Fill dirt is that part of soil used to raise the level of the ground, to fill holes in the ground, to raise garden beds, and to adjust the slope of the ground. It is usually obtained from the subsoil (soil beneath the topsoil), and it contains little or no organic matter.
So, where can you get fill dirt, and what else can you use fill dirt for? We go into the details of the answers to these questions below.
Table of Contents
Uses for Fill Dirt
Fill dirt can be used for the following purposes:
- Major Construction
- Raising Garden Beds
- Adjusting the slope/level of the ground
- Filling holes in the ground
- Repairing water drainage issues
- Holding down retaining walls
Topsoil vs. Fill Dirt vs. Compost: Differences and Similarities
Differences between Topsoil, Fill Dirt, and Compost
|Healthy topsoil usually contains organic matter.
|Contains little or no organic matter.
|Compost is organic matter. It is made from decayed animal or plant parts.
|Topsoil has varying textures. But these textures are less coarse than the texture of fill dirt.
|Fill dirt is more coarse than topsoil. It may also contain stones and tiny rocks. Also, it is harder than topsoil – it contains sand and clay.
|Compost can either be coarse or fine. Each type of compost offers a unique advantage.
|Topsoil is usually very dark because of the organic matter and mineral content.
|Since fill dirt contains little or no nutrients, it is usually lighter than topsoil.
|Compost is usually dark.
|Topsoil is essential when starting a farm or garden. You need topsoil to bury seeds, roots, tubers, or seedlings for them to grow. Then when germination starts, topsoil is the base that holds plants in place.
|The importance of fill dirt is largely structural. It would not support the growth of plants. One reason why fill dirt works well for construction is its relative lack of weed seeds compared to topsoil. The likelihood of weeds growing out of the fill dirt after construction is very low.
|Compost is usually not needed when the topsoil is rich in organic matter. But after using the topsoil repeatedly for a while, organic matter content may fall. Also, if erosion occurs, organic matter in the topsoil can be leached. In these cases, compost can be used to replenish the topsoil.
|In the soil horizon, topsoil is usually about 5 – 10 inches deep.
|The depth of the subsoil (the source of fill dirt) is well over 10 inches.
|Compost is usually applied to the surface of the soil in a thin layer. This layer is usually about 1 inch or less.
|Topsoil usually contains air.
|Fill dirt contains little or no air.
|Compost contains air.
Similarities between Topsoil and Fill Dirt
The main similarity between fill dirt and topsoil is that they both contain soil. Topsoil and fill dirt contain minerals, living organisms, and water. They also contain organic matter and gas but in varying amounts.
Similarities between Topsoil and Compost
Organic matter is the feature common to topsoil and compost. Compost is decayed organic matter, and healthy topsoil usually contains organic matter.
Shopping for Fill Dirt
Before you buy fill dirt, here are certain things you should know.
Terms You May Need to Know
Clean Fill Dirt
As the name reveals, clean fill dirt contains no contaminants or toxic substances. In other words, it is eco-friendly.
This type of fill dirt will not cause any harm to plants, animals, or humans. Clean fill dirt is sometimes treated to remove contaminants and toxic substances.
Non-Clean Fill Dirt
The existence of clean fill dirt implies the existence of non-clean fill dirt. This type of fill dirt contains contaminants.
Non-Compactable Fill Dirt
Non-compactable fill dirt is a type of fill dirt that does not become compact on applying pressure. This type of fill dirt is only good for simple uses like filling small holes in the garden and leveling the slope of your soil.
Since it does not become compact, it is not good for major construction. Hence, this type of fill dirt will not be used in building support structures.
Compactable Fill Dirt
Compactable fill dirt is great for major constructions. It becomes compact and stronger under pressure. Hence, its use in building support structures such as walkways.
This is the unit in which fill dirt is measured.
To calculate the quantity of fill dirt you need, multiply the length, width, and depth of the hole you need to fill (in feet or yards).
For instance, if the length of the hole is 1 yard, the width is 1 yard, and the depth is 1 yard. The quantity of fill dirt to get is 1 x 1 x 1 = 1 cubic yard.
If the length of the hole is 1 foot, the width is 1 foot, and the depth is 1 foot. The quantity of fill dirt to get is 1 x 1 x 1 = 1 cubic foot.
1 cubic foot = 0.037 cubic yards
1 cubic yard = 27 cubic feet
Of course, you can avoid doing these calculations yourself and use an online calculator instead.
The cost of delivery varies depending on the quantity of your order and the distance. Some sellers can deliver free of charge if you buy large quantities of fill dirt.
Where to Buy It
The Best Soil for Raised Garden Beds
If you are planning to raise your garden bed, you’ll need more than just one type of soil. The most important soil for raised garden beds is topsoil.
But to get the best soil for your raised garden bed, you have to combine topsoil, potting soil, and compost in the right proportion.
Topsoil and compost should be in the ratio of 2 to 1, and potting soil should fill the rest. In percentage, the best soil for raised garden beds contains 60% topsoil, 30% compost, and 10% potting soil.
Testing and Amending Fill Dirt
You may be able to use fill dirt as a planting medium. Normally, it does not have the right texture or have enough organic matter and air. But with soil testing and amendment, you can change that.
Soil testing involves verifying texture, pH, and drainage.
Sandy soil is coarse and cannot be molded. Clay has very fine particles, and when molded, it retains its shape.
Loamy soil particles are not as coarse as sand or as fine as clay particles. They can be molded, but if you poke them, they’ll fall apart. Loamy soil is the best for planting.
The optimal pH for soil is 6 – 7. You can check for this using a soil pH meter or a soil test kit.
To Tweak the pH
If you find that the pH of the fill dirt is above 7, you can bring it down by adding sulfur, vinegar, or aluminum sulfate. If the pH is below 6, you can raise it by adding wood ash or ground limestone.
Dig a hole with a depth of 12 inches and a width of 6 inches. Pour water into this hole until it is filled. Then wait for the water to drain completely.
After the water drains, fill the hole with water again, and monitor how long it takes to drain completely. If the drainage time exceeds 4 hours, the soil is unsuitable.
After soil testing, if you determine that the soil is not good enough, you can improve it through soil amendment. To amend fill dirt, do the following:
To Increase Organic Matter and Nutrients
Add compost to increase organic matter and nutrients in the fill dirt. Adding compost can also improve drainage and solve some other issues with fill dirt.
To Aerate Soil
The aeration of soil is improved using a device called a core aerator. This device removes clogs in the earth that prevent the percolation of water through the soil.
Alternatively, you may get an expert to amend the fill dirt for you.
Fill dirt contains little or no organic matter, so it is normally not used for planting, but for construction. However, you can optimize it for planting through soil amendment. Before you amend it, test to see the properties of the fill dirt you need to adjust.