A plant that I had for years thought was a species of clover. Anyway, was
wondering if it is nitrogen fixing as real clover or alfalfa or trefoil.

No, dear. Only legumes & certain other plants harbor nitrogen fixing bacteria.
Oxalis weeds have no redeeming features.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)