"single field" is correct and usable in written English and can be used in a variety of contexts.
For example, "The farmer cultivated a single field of corn to ensure a bountiful harvest."
"This is beyond the expertise of a single individual, a single lab, a single field".
He will probably never be able to pick a single field.
For those who like design and engineering, there isn't a single field Apple hasn't entered – or at least influenced.
Lately, it's not enough for a man to master a single job, or even a single field of endeavor.
Kickers who missed even a single field goal have been sent directly to the airport with a ticket home.
In reality, it can take over 10 years to master a single field; and that's even if you're supremely intelligent.
Over the course of a year, he photographed a single field in Northampton, Massachusetts, nearly every day.
Not a single field study on moderation or online harassment has ever been replicated in 40 years of research.
The proposed merger could not overcome the market's preference for companies that deal only in a single field, Sulzer said.
