Question

explain why fertile soil has a lot of humus?

Answer 1

As the soil contains dead matters like decaying plants etc, and some microorganisms too. And both provide nutrients to the soil by which soil gets fertile.
So if the soil contains more humus than it is more fertile as due to microorganisms and the dead decaying plants and animals.

HOPE it helps u dear.

Answer 2

The fertile soil are rich and consists of lots of microorganisms which decompose the dead organic matter or the complex dead bodies of organisms into humus which provides minerals, absorbs water and makes soil porous.