Try mushroom compost .
It should be spread on site for a month before planting .
It works like magic down here .

Being you have a large garden, think about composting this year, with that size garden you will have plenty of leftovers for the compost pile. I would also find some sawdust if possible and leaves work well also. It's an ongoing process to nurture and amend your soil so dont fret too much. You might try a cover crop in the Fall which will do wonders when you turn it under in the Spring and if you can come across some straw that does not contain many seeds, it will go a long way holding your moisture and improving your soil. For the plot that needs a quick fix I would buy a few bags of the ready made compost and work it in this Spring to give that soil a lift. Raised beds are an excellent option and I have used them with success but they are only as good as the soil you put in them. They are very manageable and you might start out with a few to see if you will like that option. I have also used 5 gallon buckets for tomatoes and peppers and eggplants because my garden area is not near as large as yours. Just keep amending your soil each year with what you can find. Your getting a good start with that manure!

You usually need a reason for raise beds such as inadequate natural soil depth, poor drainage, or want to keep your yard tidy. If you are working an estblished garden area I see no need for them.

Most of us do not start prepping the soil until spring. there is plenty of time between thawing and last threat of frost to get things done. Organic soil ammendments do not really get going/released until warm weather-early summer anyways so fall vs spring soil prep doesn't affect nutrients too much. A little fertilizer at planting time holds the babies over. You could also do what generations of gardeners have done on poor soil...use fertilizer throughout the growing season as needed. Regarding immediate need for organic soil ammendment/Compost... with two applications of manure on an area that has not been worked much I don't see a reason why you would have poor soil in dire need of compost for this year.

Thanks, Spiced Ham.
I was hoping there would be time. Here in the Northeast the growing season is fairly short. My (small) plot is part of a larger plot that I'm hoping to garden for the next several years. That's why I want to delineate it from the surrounding area.

Again, thanks to all of you for your input.

Cream

In my experience, the soil in raised beds definitely warms up sooner than in a flat garden, which is definitely a plus for your short growing season. How much sooner depends on how deep your raised beds are. Fill them with a mix of organic materials. The earthworms will mix it up for you.