Good morning and good question. My thoughts are that none of those crops absolutely need compost/manure. When I was young and busy with life raising a family and fulfilling job obligations I still gardened. I raised many a good crop with just tilling the soil and using (Gasp) 10 10 10 or Miracle Grow (Gasp-Gasp)and of course Seven(Gasp-Gasp-Gasp-O). Sometimes we forget that life can get in the way of what we want. I am organic at heart But garden produce takes priority with me. Sorry about the aside, but a good question. I am sure someone has a good answer.

Curt

Legumes seem to do okay with poor soil... they may start off slower, but once the nitrogen-fixing bacteria get going on their roots, they do fine.

Carrots aren't supposed to be fertilized heavily as it can apparently cause fine, split roots.

And I agree with Curt... I'm not crazy about synthetic fertilizers, but I use a couple good natural ones like Vegetables Alive, bloodmeal, bonemeal, and wood ash.

Sandy soil works better for root vegetables, anyway
So if it's already sandy, stop ;-)

Does your dirt tend toward clay or sand?

Heavy clay, they've all been manured at some point, so the structure isn't too bad, but as far as maintenance, trying to figure out the ones I can skip

Generally, those crops that produce a "fruit" such as tomatoes need a bit more food than say leafy greens like lettuce. But that's just a broad generalization. And those "fruiting" crops don't usually need as much nitrogen as the leafy ones do. Tell us what you plan to grow and it would be easier to be specific. And which are you going to apply, manure (fresh or aged) or compost from a variety of organic sources?

The manure is composted leaf litter and horse manure(+bedding), limed...as far as families of plants, I grow brassicas, potato/tomato family, legumes, beet family, and curcurbits...I know to lay off the manure on beets and manure heavily on potatoes, but there's gotta be some nuance with the others (even within families)

The crops that will do well without manure are beans, carrots and parsnips.

If you have clay, there are several more vegetables that will do well without the microflora of high organic matter. These are beets, chard, and all the brassica (rutabaga, turnip, radish, cabbage, arugula, kale, etc.). They will want varying degrees of fertilizer though, something like cabbage, lots of it. But it will be just as happy with urea and wood ash as it is with compost.

Chicories do reasonably well without, as do lettuce and garlic, though both are bigger and better with. I am unsure about corn.

The rest, IMHO, prefers compost. All solanaceae incl. potatoes, all cucurbitae, onions, fennel, celery, cardoon, even peas and favas. From what I wrote, you can see why I have certain rules, such as garlic and lettuce follow tomatoes.

Agree. ALL crops can benefit from regular compost because of the soil improvement it provides.

Manured compost is a whole other thing. With it focus on the leafy greens and the fruiting vegetables.

Dave

Melons, squash, and pumpkins like rich soil. Tomatoes definitely prefer rich soil.

From your list the one that needs compost the most is ONION. Then in 2nd place is Tomato. You will run out of compost by that time.

the one crop that will drain your soil of nutrients and thus probably needs it the most is corn. I highly recommend against growing corn as it ruins the soil for years.

tomatoes will grow with lower yield but since toms are the best thing to grow you always want to put compost on your toms.

Onions really are the one thing that really needs high nutrient soil. There is a form of Italian type of broccoli that needs high compost also. I forget the name.

squash and most other things can grow on poorer soil with lower yield. But not onion. Your onions will be so small that you may as well not grow them.