Fertile soil is most commonly called loam , or loamy soil.

What “fertile soil” means

Fertile soil is soil that can supply plants with enough nutrients, water, and air to support strong, healthy growth and good yields.

It usually contains plenty of organic matter (humus), a good structure, and a balanced pH that most plants can tolerate.

Why it’s often called loam

  • Loam is a mix of sand, silt, and clay in fairly balanced proportions.
  • This mix makes the soil crumbly, well‑drained but moisture‑retentive, and rich in nutrients, so it is considered the ideal, naturally fertile garden soil.

TL;DR: When people ask “what is fertile soil called?”, the usual one-word answer is loam (or loamy soil), because this soil type naturally has the properties associated with high fertility.