How to Amend Sandy Soil

by Matt Gibson

If you’ve ever gardened in sandy soil, you’ve probably already discovered that raising a garden of thriving plants in dry, fine sand can be quite a challenge. The trick is to address the problem at the source, treating your sandy soil to make it more hospitable for your flowers, vegetables, and herbs. We’ve put together this guide to help you identify sandy soil and to walk you through exactly what to do to amend the sandy soil in your garden.

Water trickles through sand quicker than through other types of soil. Sand is coarser than clay or loam—it’s actually composed of small, irregular bits of rock. Because sandy soil allows the water you diligently supply your plants to pass quickly and freely into deeper layers of earth, most of the minerals and nutrients disappear with the liquid. That means lots of the best plant food in water simply washes away before plants have time to absorb what they crave. To solve this problem, gardening experts recommend treating any dry, sandy soil where you intend to plant before the growing season begins.

Learn more. These plants grow well in sandy soil

How Can I Tell If I Have Sandy Soil?

Sandy soil can be identified by the way it feels: gritty and loose, even when the ground is wet. If you pick up a handful of sandy soil and squeeze it in your fist, it easily falls back apart as soon as you release your grip. That is because while the grains of sand are tiny, they’re also solid, with no air pockets inside. More porous soils (clay or loam) have space for water to settle, so it stays longer on the surface, where plants send out their roots. Though some plants perform best in sandy soil, like succulents and cacti, most things you’ll want to grow need a steady supply of more moisture and nutrients than sandy soil can possibly provide them.

What Are the Advantages of Sandy Soil?

If you’ll be growing many different types of plants, you may want to keep some sandy soil as-is without adding too much organic matter to the mix, as there are a handful of plants that enjoy a sandy soil base. Root vegetables, such as carrots, radishes, and beets, tend to be much happier in sandy soils than they are in clay soils. Many garden herbs require excellent drainage, and therefore also tend to perform well in sandy soils. You’ll reduce the likelihood of encountering problems with root rot and other garden maladies that result from overwatering, as the excellent drainage of sandy soils make oversaturation pretty much impossible.

Another thing to consider before you’ve amended every square inch of your sandy soil garden is the ease of the treatment process in comparison to the trouble it takes to reverse it. While turning sandy soil into a water-retentive, nutrient-rich base is a breezy chore for a lazy afternoon, you’ll need substantially more time and elbow grease to turn clay soils into sandy soil. Be sure that you know what you will plant in each bed before you amend your soil so that you alter each area exactly as needed to suit its purpose in your garden.

What Are the Disadvantages of Sandy Soil?

If you’re not cultivating root vegetables and herbs this season—or other plants that demand excellent drainage—amending your soil will most likely be necessary to give your plants the moisture and nutrients they need for success. Luckily, sandy soil can easily be altered and amended to fit your needs.

How to Amend Sandy Soil

The best sandy soil amendments are ingredients proven to increase your soil’s ability to retain water and nutrients. Adding in a healthy dose of well-rotted manure or compost is the quickest way to transform sandy soil into proper garden soil, but a lot of other factors also come into play when amending.

One of the most important things to take into account is the salt level of your soil. Sandy soils from places near the ocean tend to contain high levels of salt. While compost and manure are perfect for amending sandy soil to increase water and nutrient retention capability, both of these treatments are also high in salt. You will want to carefully monitor your garden’s salt level throughout the course of your soil’s transformation. If salt levels get too high, your plants can pay the price.

To encourage moisture retention without a heavy dose of salts, try using sphagnum peat, or a plant-only compost, both of which will contain much lower salt levels than manure or compost. Vermiculite or peat are often used as sandy soil amendments as well, though these should be paired with a good fertilizer to provide nutrients for your crops. While vermiculite and peat are great for water and nutrient retention, they lack the nutrients that your garden gains when you add organic matter, such as manure or compost. 

Method 1: Creating a Microbial Habitat

In order to amend the soil properly, you will want to increase the amount of organic matter in the soil, making it stickier. (Remember the test to find out whether soil is sandy? Sandy soil doesn’t stay stuck together at all. You can repeat this test as you amend to track your progress.)

The more organic content you incorporate with your soil, the higher its water retention capacity will be. Combining sandy soil with organic matter creates a serviceable habitat for microbial life, so fungi and bacteria can multiply, creating a nutrient-rich base for your garden beds.

Think of the soil amendments as a glue or binding compound that will help your porous, sandy soil to soften and transform into soil that’s optimized to offer the perfect mix of nutrients and the appropriate amount of drainage. What types of organic matter should you use to amend your sandy soil? We suggest compost, biochar, and coir.

Compost:

Compost is the best form of organic matter to add when you’re amending sandy soil. A good garden compost contains diverse populations of bacteria, both active and dormant, as well as beneficial fungi that will help bind the sandy soil base and improve its water and nutrient retention capabilities. Compost can be added in to make up as much as 40 percent of the finished material you’ll use to plant in.

You may be wondering—if amending with compost is the wisest choice, why are there two more options listed? Well, using compost is the best route for amending sandy soil to make your garden more productive for future use, but the process is labor intensive, and the transformation of your soil can take several growing seasons. For gardeners looking to expedite the process, biochar and coir can be used with compost to speed things up, getting your garden beds ready to go in no time.

Biochar:

Biochar is made up of organic matter, most often coconut husks or wood, that has been burned at a low temperature in a low-oxygen environment. The result is a char, which is then ground into shavings that can be added into garden soil to improve water retention and shorten the binding process that converts a sandy soil into a sticky one that can support healthy plant growth. Biochar only needs to be applied once, and it lasts for decades once applied. The compound also functions to isolate carbon in the soil, helping keep pH levels in the neutral range, where it’s just right to support a variety of healthy plant life.

Coir:

Coir is made up of dried, compressed coconut hull, which can retain up to five times its weight in water. This quality makes it a great amendment for sandy soil, especially if you need a slightly acidic soil base. Subtly acidic soils are great for growing most fruits and vegetables. So, if you are gardening to harvest lots of produce, coir is an excellent choice as a soil amendment.

In spots where you’ll grow shrubs, trees, and perennial herbs, amend the soil with 20 percent coir by applying a two-inch layer to the surface and blending it with the soil. For fruit and vegetable beds, apply a one- to two-inch layer to the ground’s surface, using a mix of coir and compost, then mix into the soil before planting your crops. 

Method 2: Mulching

Another method of amending sandy soil is to add layers of mulch, which will also help you to increase the organic content of your soil. A good layer of a high-quality mulch will reduce evaporation of water from the surface of the soil as well as keeping soil cool to the touch, which helps immensely in creating a healthy microbial environment. When the soil stays at a cool temperature, microbial life can thrive at greater depths in your garden beds, multiplying the benefits for your plants along with the bacteria and fungi.

Add a three- to four-inch layer of mulch to beds containing shrubs or trees, or a one to two inch layer for fruit and vegetable beds. Unlike with the previous treatments, don’t mix the mulch into the soil—let it rest on the surface of the ground.

Videos About Amending Sandy Soil?

If you want to skip the amendments and focus on plants that grow best in sandy soils, this is the resource for you. This lengthy video gives you a guide to gardening in well-draining soils, including the tools you will need, amendments you can make, and techniques that you can use to successfully grow shrubs, trees, and other plants that prefer to make their homes in rapidly draining soils:

This in-depth tutorial shows you how to amend the soil of your organic garden. Whether you have a clay-based soil or a sandy one, this how-to video will teach you how to alter it to better fit your needs:

Want to know which plants can thrive in sandy soil? Check out this short list, which features eight plants that are perfect for growing in sandy soils:

Don’t want to put in the work to amend your sandy soil by hand? This video teaches you how to use weeds to amend your sandy soil naturally in just a few growing seasons:

Want to Learn More About Amending Sandy Soil?

Gardener’s Supply Company covers Building Healthy Soil

Gardening Know How covers Amending Sandy Soil

Grow It Organically covers Gardening in Sandy Soil

SFGate Homeguides covers Amend Dry Sandy Soil

Permaculture Research Institute covers How to Improve Sandy Soil