I need a spray to kill the grass in our asparagus.  I was going to spray the the patch with round up before the asparagus came up but had a medical problem after which I'm restricted to lifting nor more than 10 pounds.  Backpack sprayer with roundup weighs more than I'm supposed to lift.

In a few weeks I can spray something on the asparagus if there's something that won't kill the asparagus but will kill the grass.

What, if anything can I use?