What is the perceived benefit of using "beds" in a market garden? I don't know any market gardeners in my area that plant into beds.
Last I checked the railroad ties to build 1/2 acre of raised beds would cost over $10,000. And would you want your family, friends, and beloved customers to be eating the effluent of railroad posts?
While some here might object to the idea of initially plowing the land, I don't see it to be much different than the initial land contouring that permaculturists do with bulldozers and excavators. Once you land is plowed and put into a condition you can start with, then you could develop a permie method to eliminate the need for future plowing.
If you want to do it low tech, a heavy duty rototiller can handle roots up to 1/2". Busting sod or pasture grass will take several passes and is best done when the soil is moist but not muddy. Decades ago I used a Troybilt Horse to till a field of grass. I had mowed the grass short before tilling. I recall it took four or more times over that field to get the tiller down 4-5 inches. It was work and time consuming, and I learned that I should have brought in a plow! But for a small plot, a plow isn't feasible.
For an even smaller garden bed, one could use a mattock. Hard hand labor, but it will cut through the roots and open to soil. I've done that too, and it's work. I still use a mattock to this day. It's handy for the right sort of job. But I wouldn't want to do 1/4 acre at a time. I'll grab the mattock if I need to open a new bed that's 3' by 20'.
I have a few low raised beds (3" to 5" sides) built atop pahoehoe lava. I used homegrown young tree trunks for the sides. So they cost me my labor, time, a chainsaw, and an ATV to haul them out of the woods. If I had had to buy lumber to make the beds, it surely wouldn't have made economic sense. The raised beds are a pain in the neck compared to the field beds. They dry out fast, and the sides constantly trip me. I've been working to gradually built up the soil in that area so that I can remove the logs completely some day. Raised beds may be nice for small gardens or in special locations, but I don't like them in my production gardens.
Ps- don't forget that it takes A LOT of soil to fill even a low raised bed.
Raised beds help the soil warm up sooner in the spring (which I would imagine would be important to you in Michigan) and extend the growing season a week or two in the fall. But to create wooden raised bed frames on the scale you are speaking of would require thousands of dollars. So do what Richard and many others do --- just mound the beds up 6 inches or so, and then don't step on them. geoff lawton does this. Most large-scale organic farms are doing this -- mounding their beds up but not using wood or anything else to build the sides. If the beds are no wider than 4 feet, you can easily reach from the sides and never step on the bed itself.
Further, you can build your beds on contour so they also function as swales. You can't do that very easily with wooden raised beds. If you want to add height to the bed, you dig the soil up from the pathways and toss that up on to the bed. Using wood chips in the pathways between the beds will keep things from getting to muddy and will build beautiful carbon rich soil that can be shoved on top of the beds next spring. Year after year, you'll find your beds slowly getting taller and the soil consistently getting better.
I suppose that you could run a tractor with a ripper through your soil and yank those roots loose. But if they aren't bothering anything, just leave them in the ground to rot. Long term, you'll want to go no-till.
In my biosphere, I avoid raised beds because they dry out quicker, and water is at a premium. I do a variety of sunken beds, raking back the mulch and planting the beds a bit lower than the soil surrounding them.
Ultimately, whatever you do, the goal is to build soil year after year: mulch, compost, multiple cover crops throughout the entire growing season, chop and drop, nitrogen fixers, etc. Keep every last scrap of carbon on site -- every leaf, every root, every coffee ground, every stick, stem and stalk, Just adding biomass to the top of your beds year after year will raise them. By avoiding stepping or driving on them, the worms and the normal freeze/frost cycle will decompact the soil.
Best of luck.
I am getting ready to do this same thing on the first 1/4 acre I am converting to a market garden from an existing grass pasture. My plan is to lay down 1-2 feet of mostly old hay as mulch then put a silage tarp over that until spring. Muy goal is to create a series of permanent beds 30" wide with walkways abbot 18" wide between then. Depending on what I am plantinng in each bed, I can just pull the mulch back and add compost or simply plant in through whatever mulch is left.
One reason not to till or disturb the soil is that there are millions and millions of annual seeds in there, just waiting for a chance to sprout.
G Baker wrote: I second the opinion earlier of starting with lots of mulch on the area this winter to start suppressing existing plants. If all that root mass is grass/pasture, then killing the topgrowth will cause the roots to decompose in place in the soil. After putting down mulch I would cover the whole area with a tarp, this will further suppress any existing perennials and help the mulch to be decomposed into you soil faster.
Black plastic is another way to go about this. I've seen where people will create beds with a thick layer of mulch and compost and then cover them with a roll of black plastic. Then they cut x's into the plastic when they plant their plants the first year. At the end of the first year, all that mulch will have broken down, all the remaining weed seeds should have germinated and died under the plastic, and you'll be set to pull the plastic off (if you so wish) the next growing season. Or you could leave it. The black color helps the soil warm up much quicker in spring, giving you a longer growing season.
Technically, anything thing that you throw on top of your soil is a mulch. That might be wood chips, compost, plastic, dead mafia gangsters, or white Arizona trailer-trash landscaping rock. For your long term benefit, you'll want organic bio-mass as your mulch. However, plastic is an inexpensive way to cover a lot of ground easily, and it's can be a part of an effective strategy for starting market garden beds.
Then using a rotovator with a hiller attachment behind it we made 1m wide beds, now all the people doing it advise 75cm beds as they say the equipment comes standardised in that size, but when looking at available equipment here we found nothing in that size, our walking tractors rotovator is 50cm or 85cm. so we went 1m for two passes. The beds are about 15cm higher than the paths, around 8cm higher than the ground was, Because our land is so wet all the paths run down hill so they can act as ditches, each bed is 10m long at the end there is a path wide enough to get a little trailer down (hand one) and then a ditch, then another set of 10m long beds, path ditch. Eventually I want to cover the whole field around 1.5 acres in this manner, but that would require more than just me to look after.
I am fortunate that my soil is an old lake drained 150 years ago, and the field has been unused for at least 5 years and was a horse field for 30 years before, I have great soil but a bit of issue with a water shedding layer about a foot down.
One last thing, in my climate (zone 7) it would take several years to rot out the roots and plant stalks under the plastic, we have had one piece down for two years and it's still got dead roots under it. So I would doubt that mulch is going to rot it in the time you are thinking. We do not use much as such as it's just a breeding ground for slugs, stops the water evaporating (yes I want to move as much water as I can, not keep it) and keeps the soil cold. I do use compost as mulch over winter.