I have tried many kinds of tillage for gardens, and I’ve tried no-tillage. No-tillage is a no-go unless you can lay down inches of compost. Depending on the size of the garden, this can be tons and tons of compost. In short, there is seldom anywhere near enough compost to garden this way (without tillage). So, like Adam, we must dig.
In heavy soils at least, my preference is for rotary plowing. Nothing even approaches a rotary plowed bed except a double dug bed, which is the gold standard (really an impossible standard) in tillage. Rotary plowing blows roto-tilling out of the water, and it is a considerable improvement over moldboard plowing followed by harrowing.
I happen to think that double digging is insane. It is so exhausting and time consuming that it is impractical. Sure it makes and outstanding planting bed and does a fine job of killing sod, but it is only worthwhile for the tiniest of plantings. I think the recommendation to double dig a garden does gardening in general a disservice because it is so discouraging. It is a fine way to extinguish budding enthusiasm for the hobby and harden someone against the idea of growing food for oneself.
For example, I double dug the 20×30 foot garden we kept in the city. It occupied the 80% or so of our urban lot backyard that wasn’t completely run through with my neighbors’ trees’ roots. It took over eight hours to double dig that 600 square feet, and I basically had to lie on my back for a day afterwards to recover. Out of that garden, which we tended carefully, we harvested only a little produce. Maybe enough for a few meals. The reward is simply not worth the effort.
The rotary plow achieves a comparable quality of tillage, with a fraction of the effort and time, using only a little gasoline. Like double digging, a rotary plow achieves a foot or more of deep cultivation, destroys weeds and sod, thoroughly aerates the soil, and doesn’t invert soil layers. It often achieves a fine enough seedbed for most if not all the common garden veggies (even carrots). The key, as in double digging, is to do it at the right moisture level.
With the rotary plow I essentially double dug a 60×100 foot garden, or 6000 square feet (10x the size), in about 4 hours (half the time). I used just over a gallon of gasoline (about $2.50 worth) to do this, and I went to work afterwards with only a little soreness in my wrists and a couple of calluses to show for it. A garden this size, when tended carefully, can produce a truly significant amount of produce. If one focuses on high value crops, it could “pay off” in just a few years.
Unfortunately, Rotary plows are very expensive (about $1,500) and the two wheeled tractors that drive them can be very expensive (about $3,000), so this is a great obstacle to their widespread adoption. But it is essentially a once-in-a-lifetime purchase, unlike the junk roto-tillers sold at Home Depot/Tractor Supply/Rural King which you can burn through in a few seasons. With only several hours of use annually, and conscientious maintenance, I have no doubt that these tools will last a half-century or more. These machines are made to a commercial grade and their engines are standardized, and so they can be replaced.
I’ve often thought that in a community such machines could be communally owned, or a rotary plowman could make his rounds every year and prepare everyone’s garden (this would probably be best as he is likely to take very good care of the machine and knows how to use it well). I think this would be a much better way of going about serious family-scale gardening than double digging or everyone going out an buying their own junk roto-tiller.