Plants can consume ammonia, nitrites and nitrates. In fact they need them. If you were to take an aquarium and plant it wall to wall and put .5 inches of fish per gallon (within reason) you would not have to cycle at all.
The fact that you are starting to see nitrates means you are getting close to the finish.
:thm:
Less than that. Moderately planted tanks often (IME) do not really need any bacterial filtration as it's all taken up by the plants. I never see nitrate in mine, so at some point in the nitrogen cycle the plants are taking it all up.
I don't think inches of fish mean anything, though - we live in a universe where volume increases with the cube of length.