I don’t find it necessary to feed other than an annual compost mulch, and I don’t water much in poly tunnel either, except in this years heat. Last year multi stemmed plants were producing average 12 trusses per plant so my ex-meadow underlying soil must be good.
So, the answer, as usual, depends on your individual circumstance and inclination. For me, a massive help has been Charles practice to put everything through the compost pile and treat all beds, all crops with the same input ie. compost. No separate applications of comfrey, wood ash, whatever, just compost the lot and spread annually. So simple. (Thanks Charles).
Incidentally, the next really big help is not being too concerned about rotation. So, thanks again, Charles Dowding!