i started this years crops in compost and soil left over from my last weed grow.

i use a smallish tray fill too around 3/4 full. then layout seeds. after i take compost and rub between my hands too break it up and leave a nice fine covering over seedlings.

i have used compost, potting soil, hanging basket mulch, good old garden dirt. all worked fairly well.

personaly if it is all you have too hand use it.