Hey John,
Do you have weed seed issues with hay? Straw is typically harvested from a single season grain mono-crop; hay-fields can be worked for many years (seven for alfalfa rings a bell), which makes for a cumulative accumulation of many perennial weeds.
I'm just flashing back to some of the crap hay we brought in during high school that was loaded with Canada thistle, and I sure wouldn't want to try explain to some client where all the noxious weeds came from.
But I don't seed many lawns, so maybe it isn't a problem...
