How do I improve sandy soil that dries out?
Why sandy soil loses both water and nutrients, the materials that actually hold onto them, and the planting and feeding regime that suits it.
- Difficulty
- beginner
- Time
- 2 hr
- Read
- 3 min
Short answer
Sand cannot hold water or nutrients because the particles are large and have no charge. Bulky organic matter — compost, well-rotted manure, leaf mould — is the only thing that fixes both, applied as an annual mulch rather than dug in once. Feed little and often, because anything soluble washes straight through.
Sandy soil has real advantages: it warms early, it is workable all year, and it never becomes waterlogged. The problems are drought in summer and nutrients disappearing after rain, and both come from the same physical cause.
What you'll need
- Garden compost, well-rotted manure or leaf mould
- Mulch material
- Fork
Step by step
- Confirm it is sand.Wet a handful and rub it. Sand feels gritty and will not form a ball; silt feels silky; clay feels sticky and rolls into a sausage. Sandy soil also drains almost instantly after rain.
- Add organic matter every year, not once.Organic matter breaks down fastest in warm, well-aerated sandy soil, so it needs replenishing. A 50mm layer of compost or rotted manure annually is the whole strategy.
- Mulch rather than dig it in.Spreading it on the surface and letting worms take it down is less work and does not destroy what structure there is. Digging exposes organic matter to air and burns it off faster.
- Use the bulkiest materials you can get.Leaf mould, well-rotted manure, garden compost and composted bark all last longer than fine, quick-rotting materials. Homemade leaf mould is free and excellent for this.
- Feed little and often.A single heavy dose of soluble fertiliser washes past the roots in the next downpour. Controlled-release granules or repeated small liquid feeds hold far better.
- Keep the ground covered.Bare sandy soil dries and blows. Green manures over winter, or dense planting, or mulch — anything that stops the surface being exposed.
- Water deeply and rarely.Frequent light watering wets the top 30mm and evaporates. A long soak once or twice a week drives roots downward, which is the only lasting drought protection.
- Choose plants that suit it.Mediterranean shrubs, lavender, rosemary, cistus, alliums, bearded iris and most silver-leaved plants prefer sharp drainage. Fighting the soil for moisture-lovers is a permanent job.
- Consider a raised bed for thirsty crops.Filling a bed with an improved mix gives a deeper reservoir for vegetables than trying to change a whole plot.
Tips
- Organic matter is the answer to both problems sandy soil has, which is unusual and convenient.
- Do not add clay to sandy soil in an attempt to bind it — the quantities needed are enormous and the result is usually worse.
- Sandy soil warms weeks earlier than clay, which is a real advantage for early sowings.
Common mistakes
- Digging organic matter in deeply each year — It oxidises faster when buried and mixed with air, and digging damages the fungal networks doing the work. A surface mulch lasts longer and costs less effort.
- Feeding heavily once in spring — Soluble nutrients leach straight through sand. The plants get a brief surplus and then nothing for the rest of the season.
If it doesn't work
Plants wilt within two days of watering
Cause: No water-holding capacity — Fix: Mulch thickly, water deeply and less often, and add organic matter every autumn.
Pale, hungry-looking growth despite feeding
Cause: Nutrients leaching after rain — Fix: Switch to controlled-release feed or repeated small liquid feeds.
Water runs off rather than in
Cause: Surface has dried to the point of repelling water — Fix: Water slowly and repeatedly, or apply a wetting agent. Mulch prevents recurrence.
Improvement disappears after two years
Cause: Organic matter burned off, not replenished — Fix: Make it an annual job rather than a one-off project.
Questions people ask
Should I add clay to sandy soil?
No. The quantity needed to change the texture of a bed is measured in tonnes, and getting it wrong produces something with the faults of both. Organic matter is the practical route.
How much compost does sandy soil need?
Roughly a 50mm layer over the surface each year. It sounds like a lot; in sandy soil most of it will have gone by the following autumn.
Is sandy soil bad?
Not at all. It is workable year-round, warms early, never waterlogs and suits a huge range of plants. It just needs a different regime from clay.