Alpsin

If you are getting good sized bulbs that is good but they do drain alot of nutrients especially because they are in the ground so long. Nutrient depletion is only 1 problem to look out for.

There are some Allium problems that persist in the soil for years and the more you monocrop the greater your risk becomes. I think others could weigh in on various pests, and or disease organisims that affect allium family plants.

HTH Nam

I am sure that, just like tomatoes or other veggies, allium diseases persist in the soil. I have grown onions, garlic and shallots in the same areas for three years and have no problems. Maybe got lucky. If you have had a malady affecting one of these, try moving over to another area, hard as it may be. I slap a 3" layer of fresh compost on these areas every other year and rototill it in.
hortster

I'm facing this dilemma too because of deer. Alliums are about the only thing they won't eat (though they seem to make an exception for leeks), so I can grow them in unfenced areas. This makes it impossible to rotate much out to unfenced areas, and it feels wasteful to rotate the alliums into the fences.

Alliums grow so well for me that in the spring they're about half of my quality garden beds, so there's not much left to rotate them into.

We're working on a full perimeter fence of our yard, so hopefully this is the last year that I will have this problem.

Aside from the pest issue, I don't see why you cannot plant
any vegetabloe, including garlic, in the same bed year after year.
Soil is just a medum that holds moisture and nutrients.
Of the N-P-K only N is needed to be replenished often, brcause it is water soluable and excess will be drained.
and you cannot have too much of if in the soil at any given time because plant have a crazy appetite for it.
P is pretty stable as it sticks to the soil. K is somwhere in betwee. Also, soil acidity/alkalinity has to be checked.

I believe in good tilling/turning over in the fall and spring. this will do several things; aerate, balance out nutrients and thus provide better drainage.

Aside from the pest issue, I don't see why you cannot plant
any vegetabloe, including garlic, in the same bed year after year.

Yes, but the pest issue is the issue.

Dan