Here in NC, we have heavy clay soil that’s’ not very deep. Two and a half feet down is rock, so improving soil is a big deal. Rather than “deep dig” the gardens, we build them up, deepening the soil by raising the surface. I’ve been doing this for a decade or so and have had pretty good results.
To improve the soil, I do a few things. First, at the end of harvest, I plow under the residue of crops/plants in the gardens. Very few people plow these days, but I love plowing. It makes the whole farm a compost pile. The plow flips the soil putting the new growth 6-9 inches under the soil, pulling up the composted residue that was turned over the previous winter. On top of that soil I add 6″ or so of leaves and whatever manure we have from the cows and chickens and plow that in in January. Fortunately, a local leaf collector delivers loads of leaves right to our garden. Whatever is left over, I add to my wife’s herb garden or the compost pile.
Beginning around “Plow Monday”, I begin plowing the gardens and preparing for the early Spring planting. Once I begin planting, I begin using the hand tiller instead of the tractor. I plant rows 42″ apart so there’s plenty of room to walk a tiller between the rows, keeping weeds down all summer. We use no chemical fertilizers, herbicides or pesticides, so we have to keep the gardens clean.