Gardening in Sandy Soil: How to Enrich your Soil?

By Julie Boudreau

It’s not given to everyone to garden in what I call cream: this beautiful loose soil, without rocks, rich in organic matter where everything grows by the simple force of the gaze. Oh no! Many gardeners struggle with clay, rocky or sandy soils. And each of these growing environments has its little challenges that you have to know how to take up with skill. For sandy soils, the key word is retention!

What is Sandy Soil?

All soils are a clever mix of three types of particles: sand, silt (which I also call loam), and clay. Easy to guess that sand is made of large particles (between 0.074 and 2 mm in diameter) and that at the other end of the spectrum, there is clay, whose particles are very, very fine (less than 0.05 mm). It is rare for a soil to consist of just one of these particles. A soil can contain 25% clay, 60% silt and 15% sand. If a soil contains more than 50% sand, it falls into the great group of sandy soils.

At home, soil composition can be easily assessed by placing a cup of soil in a 2 cup Mason jar. Fill with water, add a little dish soap (about a teaspoon) and stir as if it were a snow globe. The coarser particles will settle to the bottom first. After only one minute, the sand has already settled. After about 24 hours, you can quite easily distinguish the different layers of sand, silt and clay.

The Challenges of Sandy Soil

The dominant presence of sand particles will have two main effects. The first is drainage, which in this case will be too effective. The coarser the soil particles, the more water they let through. In other words, when we water sandy soil, the water does not stay in the surface soil, it quickly sinks to the depths. Thus, even after a good rain, the plants are quickly thirsty, because there is no water reserve in the ground.

The other impact of sandy soils is electrical in a way! Every nutrient in the soil has an electrical charge! It’s a matter of ions. For example, calcium and potassium are positively charged. These are called cations. Nitrogen and sulfur molecules are negatively charged. These are the anions. Contrary to grains of clay which are real cation magnets, grains of sand retain few nutrients. They are not attractive! It is therefore more difficult for sandy soil to store up and trap this precious plant food.

Finally, it should also be added that sandy soils are generally naturally acidic. The pH also has an impact on the absorption of nutrients. So it’s something to watch out for.

What happens to all those beautiful nutrient molecules that arrive in sandy soil? They are downright washed out, with rainwater or watering. This is why sandy soils, in general, are naturally poor. And here is the double challenge: in sandy soil, you have to water a lot so that the plants do not lack water. But the more you water, the more nutrients you leach out.

How to Improve Sandy Soils?

Reading this brief introduction to the composition of soils, one might think that the solution lies in adding clay, which is capable of retaining water and minerals. There is indeed bentonite clay, which is a powder that can be incorporated into sandy soil to improve retention. Basalt is also a mineral that will affect the texture of the ground.

Another part of the solution is organic matter. Manure, compost, green manures, biochar, and even straw or leaf compost can help improve the richness of sandy soil. Since this organic matter decomposes more quickly in sandy soil than in clay soil, it must be incorporated a lot and often. And pay special attention to nitrogen, which will often be deficient in this type of soil. All of these substances must be incorporated into the soil.

This is not a problem in the vegetable garden or in new beds. The best way to improve the structure of sandy soil is to do it before planting.

In the flowerbeds that have already been established, make small additions of compost, applied between the plants and incorporated into the surface using the hoe (the one with three prongs). And we will repeat the operation two or three times during the summer.

Of course, the use of organic mulches, which will be left to decompose on the spot, is also an interesting practice in sandy soils. In addition to enriching the soil, this type of mulch also limits the growth of weeds. And finally, the idea of leaving dead leaves and garden debris on the ground takes on its full meaning here, to the delight of lazy gardeners like us!

Irrigation, Frequent Watering…or None of the Above?

Since sandy soils do not retain water, watering becomes more important and essential. It only takes a few days of heat and strong sunshine to see all the plants start to wilt. The installation of an auxiliary irrigation system, which can be opened during heat waves, becomes interesting. The other option is to be very attentive to the fluctuations of the weather in order to provide the additional waterings.

But, in my opinion, the best solution remains to choose plants adapted to life in sandy soil. Thus, we avoid the burden of opening and closing the irrigation system each year and we spend more time reading than watering!