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Soil

Soil types and what they hold

Soil texture — the ratio of sand, silt and clay — sets the environment roots live in, deciding how much water is available and how fast it drains. Available water capacity (AWC) puts a number on it.

Key figures

Sandy AWC

0.04 – 0.08 cm/cm

Loam AWC

0.12 – 0.16 cm/cm

Clay AWC

0.16 – 0.20 cm/cm

Peat / organic AWC

over 0.25 cm/cm

Sandy suits

Carrots, strawberries

Loam suits

Tomatoes, zucchini, most crops

Clay suits

Lettuce, if compaction is managed

Peat suits

Container blends, seed starting

How to grow it

  1. 1

    Sandy soil drains fast and warms early, but water and nutrients leach away.

  2. 2

    Clay holds the most water but is slow to warm and prone to compaction.

  3. 3

    Loam is the reference soil: enough clay to hold water, enough sand to drain.

  4. 4

    Peat and other organic soils hold the most water and tend to be acidic.

  5. 5

    Adding organic matter raises water-holding capacity in any texture.

Sources

Every figure above comes from these pages.