Wow! That IS a long baby blanket! :teehee: Very pretty combination of yarn and stitch pattern, though.
You could use a process that is known as 'steeking' to secure the stitches on two adjacent columns of stitches (I'd pick the two center knit columns) and cut between them. After that was done you could knit on an edging, or if you wanted it to match the other exactly, you could knit a long garter strip and sew it on.
There are many tutorials on steeking out there, (including one here that I made a long time ago that isn't really what you need) so I won't try to explain what the many visuals show better, but it should be very straightforward since you have a nice, straight line of easily visible stitches to work with.
The main concern would be to make sure your stitches are very secure since it (they) will get a lot of wash and wear.
Good luck with it!