Here’s the feeding trough, so to speak, on the rooftop garden, alternatively called fertilizer alley. I keep six galvanized garbage cans stocked with the following goodies: fish bone meal (phosphorus), feather meal (nitrogen), greensand (potassium), basalt rock dust, azomite, and kelp meal (minor and trace minerals). In spring I mix up a “how-do-you-do” combo of bone, greensand, basalt, azomite, and kelp, and that gets broadcast and worked into every bed that is planted. Depending on the crop, I put in more bone meal or feather meal as additional, major nutrient supplements. I do test for the major nutrients on a bed-by-bed approach and adjust accordingly, but unless I notice some very striking symptoms of other deficiency, then I let the rocks and kelp take care of the minors and trace elements on their own, without much interference on my part. Since Azomite has both calcium and magnesium and a basic pH, it seems to be functioning in the role of liming agent, at least as far as my own pH tests go. That is something, however, of which the long-term productivity of the soil will be a much better judge, and thus far results seem good.