Most of us grow plants of one sort or another in our yards and garden spaces. This means we need soil that is suitable for whatever we decide to grow. The issue is that there are different types of soil with various pH levels that indicate how alkaline or acid the soil is. The nutrients in different types of garden soil also vary enormously.
Garden soil provides structural stability for plants as well as vital nutrients. It also needs to retain enough water for growth without causing roots to rot. Sand drains well but doesn’t retain moisture. Clay doesn’t drain well and will become waterlogged in wet weather. But adding sand to clay isn’t the solution.
Is sand good for the garden soil?
Before you add anything to your garden soil or sand garden, you need to assess what you are dealing with.
One way to categorize garden soil is by the size of the rock particles found in it. For instance, sand soil has large particles, clay soil has small particles, and silty soil has medium-sized particles.
Clay doesn’t contain much air and water drains very slowly. Sand has great aeration and drainage, but it erodes easily and doesn’t hold nutrients or water well. Silt has properties between the two.
Loam is the ideal soil for most plants. The soil structure of loam contains equal amounts of the three types, so it drains well and holds sufficient moisture. It also allows sufficient air to reach the roots.
Once you know what sort of soil you have in your garden you can decide what, if anything, you need to do to improve it. Sand can sometimes be used to improve the properties of garden soil, but its usefulness is limited.
Also, there isn’t 100% agreement by those in the horticultural and agricultural industries about when and how sand should be added to garden soil. For this reason, we have sourced a variety of recommendations. In most instances, the approach suggested is based on the type of soil typically found in the areas where various experts are based.
Should you add sand to clay soil?
There is a common misconception that adding sand to clay soil will solve the problem of drainage through clay. If the soil is very heavy, the sand may help to lighten it, but more importantly, you need to loosen the soil and add organic matter.
Rosie Lerner from Purdue University’s Extension Service for Home Gardeners advises adding “a good amount” of organic matter to heavy, compacted soil, including clay. This may be in the form of animal manure, compost, organic mulch, or cover crops.
She maintains that adding some sand with the organic matter is okay, but doesn’t advise adding sand on its own. This is simply because sand doesn’t have the nutrient- and water-holding capabilities that compost and other organic matter offer.
Extension professors from The University of Maine recommend amending heavy clay soil by adding organic matter and not sand. This is because as it decomposes, the organic matter becomes humus that literally glues the soil particles together into aggregates. The humus improves drainage.
Similarly, organic matter – not clay – will increase the ability of sandy soil to hold nutrients and water.
Ashley Troth of the North Carolina Cooperative Extension in Durham County warns that peat moss and sand aren’t recommended for improving clay soil. He also warns against trying to improve garden soil with commercial topsoil.
It’s interesting to note that the typical soils in Troth’s part of the world are known as Ultisols. They are a result of heavy rain leaching out many of the nutrients in the soil combined with warm weather that prevents organic matter from being naturally accumulated.
When should I use sand in my garden soil?
Joseph Masabni from the Texas A&M AgriLife Extension recommends adding gypsum to heavy clay soil to loosen it and make it easier to work. However, he also says you can add a mixture of sand and organic matter to clay soil to make it more workable.
When should I avoid using sand in my garden soil?
If you have highly sandy soil you certainly don’t want to use additional sand in your garden. Even if you have a mix of sand-clay soil, don’t add more sand.
What these two soil types (sand-clay) have in common is an inability to hold nutrients and water in the proportions needed for healthy plant growth. Sandy soil doesn’t hold enough water and clay soil holds too much water.
Forget the sand and add at least two inches of organic matter over the top of sandy soil and/or clay soil. Then loosen the soil and dig the organic, manure, or mulch into your garden soil.
How to add sand to garden soil?
Joseph Masabni, mentioned above, suggests mixing 2 inches of clean sand with 3 inches of organic like leaves into garden soil. Do this in winter when most plants are dormant.
You can also add sand to compost and then dig this into your garden soil. This approach works best when you have clay soil.
What kind of sand do you mix with soil?
The University of Florida Institute of Food and Agricultural Sciences has an interesting post about the homemade potting mix.
Even though it’s intended for use when growing seedlings, transplants, and a wide range of container plants, there is no reason why you shouldn’t use it in raised planters. You can also add it to garden beds that need a bit of a boost.
One of the most important factors they highlight is the need for good quality potting soil to retain moisture while allowing for water flow and air exchange. These are elements we have already highlighted.
What we want to highlight here is their suggestion that coarse sand, including builder’s sand “is best.” They say to avoid plaster sand and other fine sands because they tend to create a dense mix.
The extension professors from The University of Maine make comments and recommendations about garden soil. For instance, beach sand has many large pores, which are the spaces between the sand particles, that allow water to drain much too quickly for growing most plants.
Of course, beach sand also has some salt content that isn’t beneficial to plants.
To add sand or not add sand to your garden soil will be a decision relating to your personal soil improvement program. Whatever your approach, improving your soil will be an ongoing task.