Thanks for clarifying. I do feel a bit of lower back strain after doing barbell rows, so what about those barbell rows you do lying on your chest on a bench? Much different from standing free?
If you take the lower back/core supporting factor out, you'll definitely find that it's easier on the lower back for strain. T-Bar supported rows are good for that, they never really feel "right" to me when I do them, but they don't tax my lower back at all, which is a nice change.
Also, with barbel rows, you'll find less strain if you do them with the torso at about 45 degrees vs. parallel to the floor and by keeping the bar as close to the body as possible. It will activate the upper back muscles slightly differently than a wider grip pulling to the middle chest (more latissimus activation vs. other middle back/rear deltoid work), but is still a useful way to row and tends to be less stressful on the lower back.