Get rabbit/chicken crap, mix in sawdust from pine or oak (very very small chips not powder) add oak leafs if you have any and a little water let set for a week in the sealed 30/50gal bag, keep mixing this mix in the soil up to a week before planting season keeping the ground moist (not saturated), I also make a small mixture in a plastic lined wheel borrow (1/8 filled) rest filled with water, let the water set over night, I use the water for watering the asparagus, asparagus is a pig, don't have other plants nearby. Think of the wood chips as a time release capsule
I freeze and also pickle them though I don't plant a lot of them. Fresh one's I oven roast, garlic and butter when done add parmesan cheese.
I mix cow/chicken manure after growing season when I till the garden (twice before the freeze sets in) then cover the garden in straw, the thing with asparagus the ground needs to stay rich all year long.
Potatoes and onions could practically be grown year around hay being an excellent insulator. If you use hay in conjunction to a green house you will be surprised what can be grown in the winter months. Take a bale of hay dig out the center, put in a planter with only the top of the planter shown filled with rich soil, put black plastic over the bale of hay though cut the top around the planter then cover with heavy mill clear plastic this allows sun light on the soil in the planter
EDITED: The black plastic absorbs the heat, the hay holds and radiates the heat keeping the soil warm enough for growing.