I’ve never tried putting fert in with the seed, and no, the new drill doesn’t have a separate fert box (I don’t think i’d Spec one if it was available tbh). I have mixed slug pellets with seed on occasion (where Glastir wouldn’t let me apply on the surface after drilling), and they seemed to stay mixed OK. I suspect fert would be the same? Where I have wanted to put fert in the seedbed, i’ve Run over it quickly with the fert spreader beforehand, then the drill has mixed it into the seeding zone anyway. I don’t really see a need unless P index is on the floor (as it was when I arrived here), as N is surely mobile enough to move down from surface spreading anyway.