Oh strong-ridged and deeply hollowed
Nose of mine! what will you not be smelling?
What tactless asses we are, you and I, boney nose
Always indiscriminate, always unashamed
And now it is the souring flowers of the bedraggled
Poplars: a festering pulp on the wet earth
Beneath them. With what deep thirst
We quicken our desires
To that rank odor of a passing springtime!
Can you not be decent? Can you not reserve your ardors
For something less unlovely? What girl will care
For us, do you think, if we continue in these ways?
William Carlos Williams is saying that he has a strong, bold nose. The person is looking for anything. Dogs famously live with their nose, and generally their low to the ground. Here, he is operating in the Whitman tradition of his willingness to go low with his senses. 
 (Source:  Coursera – Modern Poetry  )
Smell