many grass seeds will not flow through a standard grain drill,
some times one can get to flow with a filler, Oats sand wheat, other, the seeds are many times fluffy and bridge and will ball up on top of the seed cup,
small round seeds will flow, but the fluffy ones will not, and on some seeds one will need the attachment called a grass seeder, (alfalfa seeder).
mixing seeds usaly does not work well, as the small heaver seeds will work there way to the bottom and not stay mixed, thus one nearly needs (depending on the seed) three boxes and seed cups, one for the very small seeds like alfalfa and switch grass, some larger smooth type of seeds, in a regular grain box, and the fluffy seeds, broam, blue grama, blue stem and Indian grass, and others that are similar, need some thing different, I use a old drop fertilizer spreader, (I made a seed basket, have heard they work on with the fertilizer feed, but never tried, it, I copied the basket from the John Deere, manual that goes with mine, or a special drill with fingered seed cups and agitator mixer
I use the drop spreader in front of a grain drill with the small seed box, on it pull both at once,
