How do you feed sub-irrigation soil planters?

I'm about to start my first grow, and will attempt an organic 'living' soil in an outdoor SIP system*. I have no idea if I will need to feed after planting. If so, how? Can I top dress if I'm not top watering? Drain the reservoir, top feed, then flush it out after? Foliar feed?

If this is the wrong sub, please point me in the right direction. And, of course, thank you in advance for any advice.

*I'm planning on a noobwannaB style SIP system. Each 25 gallon cloth pot will sit atop a layer of lava or perlite contained in half of a 55 gallon drum.

Why would you need to feed it after? If it's an organic living soil doesn't that provide everything it should need? Excuse the ignorance cause I have mostly done hydro. My only soil grow I didn't supplement anything except CaliMag.

Well, if all goes well I won't need to feed. But I want a backup plan in case of deficiency.

I'd think depending on the deficiency top feeding or foliar would both be fine. Like I think you can fix iron, magnesium, manganese, and calcium with foliar? But the other ones you should water? Take that with a grain of salt, as I don't know shit compared to a lot of these guys.