When starting a new farm, you may realize that small rocks, gravel, and pebbles impact the properties of your soil in ways that may be unfavorable. In some cases, like when building specialty garden beds or making a soil mix for starting seeds, you may decide to remove small rocks to improve your soil quality. In other cases, like when farming large areas of land, removing them may be unnecessary or too labor-intensive.
Read on to learn more on how to remove small rocks from soil + watch some informative Youtube videos below for a visual guide!
What You'll Learn Today
- Small Rocks Affect Soil Quality
- How Important Is It To Remove Small Rocks?
- Removing Small Rocks With A Soil Sifter
- What To Do With Small Rocks
- Improving Soil With Excessive Amounts of Small Rocks
Small Rocks Affect Soil Quality
Rocks don’t directly contribute to your soil fertility since they hold little nutrients and are largely void of life. While they don’t usually cause issues directly, they do take up valuable space that could otherwise be filled with finer biologically active sediments.
Thus if you have a high percentage of rocks in your soil (15% or more) you may choose to remove them to provide more space for better soil.
Impact Of Small Rocks On Soil Quality:
- Reduced water retention
- Reduces nutrient holding capacity
- Can be cumbersome
- Biologically inactive
- Can affect the growth of root crops
Small Rocks Increase Drainage
One of the biggest impacts small rocks can have on your soil is greatly increasing drainage. If you live in a climate with excessive rain this could be beneficial, but if you have a significant dry season then it’s unlikely to serve in your favor.
How Important Is It To Remove Small Rocks?
For most gardening and agricultural projects removing small rocks is not very important and is too labor expensive. Alternatively, if you want to make high-quality soil for whatever reason then you may want to remove them.
Reasons To Remove Small Rocks:
- Soil for starting seeds
- Soil for bio-intensive beds
- Soil for container gardening
- Planting of certain root crops
- When rock content exceeds 25%
- To reduce drainage in dry climates
Reasons To Leave Small Rocks:
- Working with larger scale agriculture
- To increase drainage in wet climates
- When rock content is less than 15%
- When removing rocks seems too labor intensive
Removing Small Rocks With A Soil Sifter
The best tool to remove small rocks is a Soil Sifter. This tool usually consists of a rectangular or square frame that has a metal mesh with 1/2” or 1/4” holes attached to the bottom. Sometimes they have handles that allow you to move the sifter with two people.
Using A Soil Sifter With Two People
One of the quickest ways to use a soil sifter is by placing your soil on the mesh and then shaking it back and forth with the help of another person. Preferably you will sift the soil onto a tarp to avoid mixing it with unsifted soil. Place the small rocks aside and fill again.
Using A Soil Sifter Alone
There are two main ways to use a soil sifter without the help of another person. The first is done by placing your filter on top of a wheelbarrow or container and moving the soil around by hand, allowing the fiber sediments to pass through.
Otherwise, if you have a larger rectangular sifter you can place it at a 40-degree angle and throw shovel-fulls of soil at the soil sifter. Finer sediments will pass through to the bottom while small rocks will gently roll down the sifter.
In some cases you may be able to separate a large quantity of rocks just using a rake. Circular “washing machine” like soil sitters known as Soil Tremblers are another good option if you plan to sift a lot of soil.
What To Do With Small Rocks
After having separated small rocks from your soil you may be wondering what you can do with them. Thankfully they can be a great material.
Common Uses For Small Rocks:
- Soil for a succulent or dry garden
- To improve drainage
- Slow water in drainage ways
- As filler material
- Can act as a natural mulch
- As a construction material
- As decoration in the garden
- As a thermal mass
Improving Soil With Excessive Amounts of Small Rocks
First, you’ll want to remove as many of the rocks as you have the motivation to do so. Any soils with more than 20% small rocks will be difficult to cultivate so aim below this number.
You will then want to amend your soil with compost, biochar, and other natural soil amendments. Mix these into your soil and then lay a thick layer of plant-based mulch on your soil surface. With this and other regenerative agricultural practices, you can mitigate any negative impacts that small rocks may have on your soil.