Having used a tiller for some years, I'd advise only using it to
prepare the bed. It really beats using a shovel in heavy soil. Make the
trench, amend the soil, put the soil back.

I stopped using the tiller on my prepared beds, let the soil create a
structure again. If I was to add further compost, then I'd consider
using the tiller again... But it's a bit hard to lift the 6HP Troybilt
high enough to get into my beds.

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