make good his ground

This needs more context. Fortunately it is easy to find the original. As far as I can tell, "makes good his ground" is part of a metaphorical idea and means something like "ensures that the students are properly and thoroughly instructed". To me, "holds his ground" doesn't seem right. Where did you see this annotation? Does it seem to be from a reliable source?

rpshThe annotation says that it means 'hold his ground'. Do you think it's correct?

No.
It means to establish a sound platform as a basis for further argument or development of a theory.

It stems from a famous magazine about English in China. And the annotation is made by some experts, I think, at least recognized by the editor...

Could I consider the writer likens the teacher as a farmer here? He makes his field good, then the field can be a better place to bear fruit, namely, can cultivate more better students?

rpshCould I consider the writer likens the teacher as a farmer here? He makes his field good, then the field can be a better place to bear fruit, namely, can cultivate more better students?

No, he is likened to a preacher or missionary.

It is the place where the professor becomes eloquent, and is a missionary and a preacher, displaying his science

So vivid! Thank you!