is the rhizosphere and top soil the same thing

No, they are not the same. Topsoil refers to the uppermost soil layer (approx. top 5–30 cm), containing organic matter and nutrients. The rhizosphere is a microscopic zone within the topsoil, surrounding plant roots and directly influenced by them. All rhizosphere is within topsoil, but not all topsoil is rhizospheric. Their properties differ due to root activities and microbial concentration.