I noticed a similar phrase recurring twice in the conversation between Effi's parents in Chapter V of Theodor Fontane's Effi Briest, which I'm reading online:
Miss Hulda had clinked her glass too hard against Lieutenant Nienkerk's.
"Of course, half asleep and always has been, and lying under the elder tree has obviously not improved matters. A silly person, and I don't understand Nienkerk."
"I understand him perfectly."
"But he can't marry her."
"His purpose, then?"
"A wide field, Luise."
"So now you admit it. In talking with me you have always denied, yes, always denied that the wife is in a condition of restraint."
"Yes, Luise, I have. But what is the use of discussing that now? It is really too wide a field."
In the first of these passages, the meaning of "A wide field" seems clear to me: their conversation suggests that Nienkerk was flirting with Hulda although he knew that he wouldn't commit to a married relationship with her; the "wide field" means he wanted to keep his romantic options open.
In the second passage, which occurs at the very end of Chapter V, the meaning of "too wide a field" is more obscure to me. What field, in this context, is too wide?
Is there any significance in this phrase being repeated twice in quick succession? Does it foreshadow later events in the story, or is it a well-known proverb in German with some meaning that I'm missing from reading a translation?