On the assumption you mean Zantedeschia of some variety when you say calla lily, I'm not aware of any special feeding regime for these other than what I say below. If you have one of the coloured varieties with spotted leaves, these are not frost hardy, so need to be brought inside to overwinter; there is a recommendation that you feed with a high nitrogen fertiliser (something like ordinary Phostrogen will do) until the flowers start, then withhold feed, then when flowering is over, use tomato feed. In practice, you don't have to do any of this.

Zantedeschia aethiopica Crowborough, though (white with plain leaves) is hardy outdoors, and is an herbaceous perennial, and requires no special attention other than damp soil.