Topsoil: What It Is and How Much You Need

Loading Garden

Topsoil vs. Compost vs. Fill Dirt

These three get mixed up at the garden center constantly, and choosing wrong is the difference between a bed that grows and a bed that sulks. The short version: topsoil is the growing medium, compost is the fertility booster you blend into it, and fill dirt is structural material you use to build up grade, not to plant in.

Material	What it is	Best use
Topsoil	Mineral soil (sand/silt/clay) plus organic matter and microbes	Bulk growing medium for lawns and beds
Compost	Fully decomposed organic matter, roughly 1-1-1 NPK	Fertility and structure amendment, blended in
Fill dirt	Subsoil with little or no organic matter, often unscreened	Grading, leveling, filling deep low spots

Compost is richer in nutrients than topsoil but too intense to plant directly into at full strength; it is a supplement, not a base. Fill dirt is cheap and stable, which makes it right for raising a low corner of the yard or backfilling, but it will not feed a plant. When someone tells me their new bed "just won't grow," the answer is usually that they planted into fill dirt.

Topsoil: What It Is and How Much You Need

Topsoil

What Topsoil Actually Is

Topsoil vs. Compost vs. Fill Dirt

How Much Topsoil You Need

Building a Bed: My 50/50 Mix

Common Topsoil Questions