Some usable pairings that come to mind:mimi2 said:"The .........in the south of VietNam is very rich and fertile."
a. ground (ground tends to be used when a destination (on the ground) or an electrical termination, or when discussing firmness, stability, or territory in dispute).
b. soil (soil tends to be used most when describing growing things)
c. land (land tends to describe boundaries and scenery)
d. earth possible 2nd choice (earth can be used to discuss growing things, but is usually used when referring to the entire planet)