They do not see cattle cropping red winter grass, They do not hear Snow water going down under culverts Shallow and clear.
You know those sensory deprivation tanks where you can just float in darkness and bliss out to the sounds of silence? Well, even if you don't, our speaker seems to liken that condition to all women. They can't seem to see or hear things.
More specifically, women can't see the poetic image of cows eating ("cropping") grass in a winter field.
They also can't hear the melting snow as it runs under a drainage ditch ("culvert").
It sure seems like our speaker is faulting women for a lack of perception. She (and we're just guessing that our speaker is a "she" at this point) seems to think that they're not capable of noticing the minute beauty of the natural world.
Interestingly, our speaker doesn't say why she thinks this is the case (as in, maybe they're too busy to stand around and check out cows having lunch). All the same, we get the feeling that, to her, this is another shortcoming in women.
Some good news, however: the rhyme scheme of the poem seems to be holding up. "Form and Meter" has you covered when it comes to all that stuff.