There is something about the way Laertes says this that expresses his love for his sister. It has a softness, an affection for both her and the earth. It is a beautiful way to say this.
The priest, who is an asshole who would rather throne stones on her, would say “Throw her in the ground” “Toss her into the grave” “get the body in the dirt.”
But Laertes finds a way to express the moment to bury his sister with care and gentleness.