I've read somewhere that summer caulis are greedy feeders and are best grown on a manured bed(not fresh manure) I thought brassicas didnt like manure as its too acid and need a higher pH. so does it mean you have to grow them on a separate bed to cabbages/leeks/sprouts. :-\
Couldn't you just add some lime?
you'd probably be growing caulis on a bed that was heavily manured last year, say for spuds, so it will still be good, rich and lovely for brassicas - as barnowl says, add lime if the land needs it and feed as you go - they like seaweed