Question

why is subsoil not suitable for growing crops?

Answer 1

Sub soil is not suitable for growing crops because its soil particles are not much fertile. It contains less humus. It does not have as nutrients as top soil have. Etc.
Hope it helps...!!!

Answer 2

The subsoil is not as suitable for growing crops as top soil because it contains very less humus.  

EXPLANATION:

The humus is the organic matter that is formed by the falling leaves and remains of a plant. These organic matters provide a good assistance for the growth of plants as they are rich in nitrogen and other nutrient content.

Though the sub-soil does not contain humus it contains mineral salts that help in plant growth and development, some farmers do mix top and sub soil for better yield.