I have never planted anything 1/8" to 1/4". My broccoli seedlings, carrots, all the teeny stuff, get planted about 1/2", just because that's how I've always planted them.

I get 90-100% germination on everything.

Here is a link that might be useful: loribees garden blog

I like your raised beds! 1/2" sounds sensible. 1" seems pretty deep for a tiny seed. I think I'll keep it simple, and maybe apply row covers after the next sowing if I'm losing too many seeds to the elements.

Small seeds can be covered a bit deeper in raised beds with loose soil. For soils that might crust, they can be covered with damp peat moss that is tamped down. Of course, burlap, boards, and weed barriers can be useful to keep the soil moist until the seedlings emerge.

The problem with burying seeds too deep: the seed contains the nutrition that the seed needs until it sprouts, forms leaves and developing chlorophyll/photosynthesis; if the tiny plant has to struggle too much to get to the light, it can expend the available nutrition and exhaust itself.

As is commonly referred to with weed seeds, the ones that sprout are the ones in the top 1/4 to 1/2" of soil, the others stay dormant until better conditions are provided.

Good to know. The ones I recently planted at 1/4" to 1/2" seem to have survived a couple of heavy rainstorms, so I think I'll stick with the shallower depths.

I'll econd Wayne's recommendation on using a moisture holding ground cover. I use straw or row cover fabric to accomplish the same purpose.

Planting anything deep is a risky venture b/c seeds can rot if too wet or may never penetrate through dry, hard soil. As a rule-of-thumb you are better to get seedlings emerged ASAP and then you can hill soil around then later.