...it makes targeting the watering better. Less run off. More water where I want it.
...as the seedling grows, I scope dirt back in to fill the depression, thus entrenching the plant deeper into the soil for better growth, stability, and production.
Ok, here's an example.
I started some daikon seed in trays then transplanted the seedlings out into the garden into little depressions I call bowls. Actually I scooped out the soil about the size of a soup bowl and planted the seedling down in the bottom. It's now easy to gently water it. Below, all the dark circles are the watered in seedlings.
After the initial watering, I apply a very, very light mulch.
Pictured above, two weeks later the daikon seedlings have grown. I gently fill in the bowl by hand scooping the surrounding soil back in. With the soil once again level, it's time to apply more mulch. The seedlings are large enough now not to get lost in the mulch.
Well, not completely lost, but hard to see. But now they will grow quite rapidly. Within a week they will be well above the mulch.
Sometimes I will make a long furrow running the length of a bed (about 20' long). I tend to do this for potatoes and sweet potatoes more so than other crops. These get planted at the bottom of the furrow, then over the course of a couple weeks I fill the furrow in by scoping in the surrounding soil. Then the next step is applying a thick mulch.