The fertilizer will wash down through the soil horizons by the spring time?
Depends on the fertilizer you use, and where you live.
If you use fast acting fertilizer, and have a winter ground cover there are 2 effects.......the ground cover will utilize 'some' of the fertilizer, but leave fertilizer of it's own behind, if it's tilled under in early spring.
If no ground cover, and not tilled under.....fertilizer can be destroyed before spring arrives.
As far as 'washing out" I haven't experience that, but in a 'flood prone area' it probably will happen.
Most of the fertilizer I've seen(whether it be manure or store bought), seems to work the best in my area in the second year.
I've read that a lot of the fertilizer needs to 'work' for a while before it can actually be utilized by plants for food.
I know I'm not using the correct terminoligy for what I'm describing, but the philosophy is the same. If you don't have major run-off problems, the second year is best for fertility.
So I fertilize in the fall, and don't allow anything to grow. In my soil here, it seems to work well.
Don't get me wrong, I still fertilize in the spring, but the fall fertilizing and the addition of lime(slow acting), seems to work well.
Although, I have been thinking of sowing a crop of winter wheat or something, then tilling it under in the spring to see what happens.
I will have 2 gardens growing next year, one at my house, and the other at my BIL's place in Maryland that we've had going for 6 or 7 years now.