It's worth remembering that a lot of the best soil and nutrients are in the turf. If you make a stack of the turf, it will rot down the grass in 3-6 months and produce good soil for planting seeds or to spread back on the soil.
If you dig the subsoil once the turf is removed, it will produce a better draining bed for vegetables but may need some well rotted manure or compost dug into it before it will be productive. You could use chemical fertilisers, but...
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