Most herbicides, roundup being the notable exception, are broad leaf herbicides and would thus kill alfalfa. They might be spraying the ditches or fallow fields with something to kill weeds. I really doubt anything would still be active by the time you use it.

I don't fertilize my lawn, but there is no reason not to dump them directly in the garden, they make an excellent mulch, in fact, thats all I use.

Alfalfa pellets are the only fertilizer I've used on what little grass I have left. Also it does get a top dressing of compost now and then.

I'm not sure what kind of fertilizer you're using on the grass but if you're using the mowed grass as a mulch then it's probably not an issue. As long as you wait a few days after application to mow then it should be fine.

many thanks!

Personally I wouldn't worry. Here all spraying if they do any is in the late winter and early spring before they start watering. I know a few that do spray after the weeds start. But they always water at least once or twice before they lay it down for hay. I don't feel you will see any damage but I have learned not to say you never will. I use loose alfalfa from the hay lot for mulch every year and have yet to see any problems. I do know how my growers handle their fields also and that helps. Fertilizing wouldn't concern me as long as it doesn't have a weed killer in it which you say yours don't. I used to get grass clippings from a local rec dept. I asked that they mow once after they sprayed. I never saw any problems till a new director took over and would spray and not tell me. So I just quit taking the clippings. Jay