Is sand good for compost?

QUESTION: Is sand good for compost?

ANSWER: Using sand as one of the ingredients in your compost will add bulk to your compost pile to fill it out, along with injecting the mixture with trace minerals from the sand. In any type of soil, a bit of sand will increase drainage, and its fine particles will help break up any clods or clumps. Adding some sand will also aerate the soil to increase the circulation of oxygen, encouraging stronger, healthier root systems in your plants. 

However, you don’t want to add just any kind of sand to your compost, as some types of sand contain more lime or sodium than is good for plants. These varieties of sand can have a detrimental effect on your garden. You’ll want to opt for a horticultural quality sand, which you can find at a nursery or garden center. Sand from the great outdoors should be avoided unless you are certain of its mineral content and know the sand is safe to use in your garden. 

Some gardeners recycle sand they procure from foundries—sand from brass or bronze foundries should not be put to use in the garden because it contains hazardous chemicals. Instead, if you choose to recycle sand from a foundry by using it in the garden, opt for sand that comes from an aluminum, iron, or steel foundry.

As an alternative to adding sand to your compost pile as one of its ingredients, you can also mix sand with mature compost to create your own potting soil blend. You’ll want to use a blend of half compost and half sand in your homemade potting soil.

You can either mix your compost and potting soil together in a wheelbarrow or on a plastic tarp, or you can alternate one-inch layers of compost and sand in your plant containers, then mix the layers well to create a uniform soil blend. In addition to using this mixture as potting soil, you can also add a three-inch layer of the compost and sand over the surface of your garden beds, then mix it down into the soil to a depth of six to 12 inches, just as you would when amending your soil with compost alone.

If you’re considering using sand and compost as a potting soil, you may be interested in this video from California Gardening, which puts a sand and compost potting soil blend to the test with several different plant species to see how they will perform growing in it.

A compost that includes sand, or a soil amendment blend made up of half compost and half sand,  is particularly useful for gardeners who want to loosen up a heavy, clay-based soil when they mix in their compost, because the addition of sand will improve the texture of clay soils, making them lighter and more similar to loam.

Whereas clay soils tend to hold tight to the moisture they receive, becoming sludgy and oversaturated, a sand and compost amendment will correct this issue and allow water to drain more freely through the soil. To amend clay soil with compost and sand, begin by mixing one part sand in per 10 parts of your clay soil. Then add in your compost, also at a ratio of one part compost to 10 parts soil/sand mixture. Mix well until the components are thoroughly combined.