Minerals and Organic acids are always worth using mate. Thats the funny thing, NPK is over rated, you can get that most places, but if you dont have minerals, then so many other plant processes fail and the result is awful. we can get away with an N flutter, but if we lose micros, then we suffer big time esp on taste and oil returns :) I use humates once a month in my garden, spraying when light levels are low, and I use volcanic rock dust so like Azomite mate. I mix it in to a base at 2KG per 1M2 , then I usually dont need to bother for 2-3 years just top dressing it with wood chip mulch as needed after that.