Question

Fertile soil has lots of humus .give reason

Answer 1

Fertile soil contains lots of microorganisms which decompose the complex dead bodies of plants and animals into a simple substance called Humus.  This is so because humus contains remains of dead plants and animals which in turn contain carbon and nitrogen which when decomposed by microorganisms gives carbon dioxide and complex nitrogen compounds are used by plants as soluble compounds.

Answer 2

more the humus the  soil contains it is more fertile . fertile soil also contains lot of decayed microorganisms . which is called humus