The quality of the soil is but one of the many parameters one needs to juggle when maintaining a veggie patch. Some of the others being: sunlight, water, PH levels, bugs. fertiliser, and crop rotation.
To this end, I have a continual stream of compost on the tumble. Not mulch, which to my mind is purely for water retention, and has not undergone the necessary decomposition. Not humus, as I tend to think of this as containing decaying animal matter as well as decaying vegetable matter.
I suspect I do not tumble my compost for long enough. Look at this latest batch that I have just layered into the low bed. There were 8.5 bucket loads (an 8L bucket). Can you see the complete leaves in amongst the rest? If this were 'mature' compost, the entire mix would be more friable, rich but more like soil..
But, I am getting there ...