If it is clay it is going to have plenty of p and K in it, Ca depends on what the rock it formed from was. But do chuck some peat in there when you till for the carbon. A tea or innoculant, something to get biology going down there would not be a bad idea either.
I would not be too worried about amending that soil other than gypsum CaSO4 which will allow minerals from the mound to leach into that soil which will open it up and allow roots to grow there.
You guys are lucky to be able to grow the plants as tall as you want.
I would not be too worried about amending that soil other than gypsum CaSO4 which will allow minerals from the mound to leach into that soil which will open it up and allow roots to grow there.
You guys are lucky to be able to grow the plants as tall as you want.