How can I improve clay or sandy allotment soil?

By the Tilthwick team

Sources awaiting check

Add mature organic matter regularly and protect the soil surface. Garden compost can improve structure and aeration, help sandy soil retain moisture and help heavy clay soil drain more effectively.

Work with the existing soil

First observe drainage, texture and how quickly beds dry. Avoid working saturated clay because foot traffic and cultivation can compact it. On sandy soil, mulch helps slow summer evaporation. In either case, repeated modest additions are more useful than trying to replace the soil wholesale.

The RHS says home-made compost adds organic matter and supports soil structure and biodiversity. No-dig management places that material on the surface, where soil organisms gradually incorporate it; light forking is another option where appropriate.

Keep inputs known and suitable

Use mature compost or other well-rotted organic matter. Ask what delivered material contains and do not accept unknown waste as “topsoil”. A pH test can inform planting choices, but pH and texture are different properties: adding lime does not turn clay into another soil type.

Sources

  • RHS: Making and using garden compost on a plot checked 14 Nov 2026
  • RHS: RHS no-dig: a new bed can be planted once made when its organic mulch is well rotted and sufficiently deep; minimise traffic on saturated beds and use planks to spread weight when needed awaiting check