How-to Guide
How to Improve Sandy Soil
The short answer
Sandy soil drains fast and loses water and nutrients quickly because its particles are large with big gaps between them. The fix is organic matter: spread 2-4 inches of finished compost or aged manure and work it into the top 6-8 inches. The fine, spongy organic particles fill the gaps and let sandy soil hold moisture and nutrients like a sponge.
Keep adding organic matter each year, and use mulch and cover crops to build it up over time. One caution from extension research: don't push organic matter above about 10% — beyond that, drainage can get too slow and invite root disease.
Why organic matter is the answer
Sand can't hold water or nutrients because there's nothing for them to cling to. Compost, leaf mold, and aged manure add fine, absorbent material that fills the pore spaces, so water and dissolved nutrients stay in the root zone instead of draining straight through. Over time this also improves aeration and structure.
How to do it
- 1Add compost or aged manure — Spread 2-4 inches of well-decomposed compost or aged manure over the bed.
- 2Work it in — Incorporate it into the top 6-8 inches of soil.
- 3Mulch and repeat — Keep the surface mulched, and add organic matter again each season — sandy soil burns through it faster than clay.
✔ Cover crops (green manures) grown and turned under are a low-cost way to keep building organic matter in sandy beds.
When this doesn't apply
→ Don't chase ever-higher organic matter — Rutgers Extension notes capping around 10%; past that, drainage slows too much and root diseases increase.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Colorado State University Extension — Choosing a Soil Amendment — Well-decomposed organic amendments (compost, aged manure) improve the water- and nutrient-holding capacity of sandy soils; incorporate into the top several inches.
- Oregon State University Extension — Add organic matter to improve most garden soils — Organic matter improves aeration, water infiltration, and water- and nutrient-holding capacity of soils, including sandy soils.
- Rutgers NJAES — Mulches / soil organic matter guidance — Excessively high soil organic matter can slow drainage and raise root-disease risk; aim to build, not overload.