google up foliar feeding....many tropical forest dwellers pull in nutrients this way, leaf residue, insect crap and body parts, bird crap, dust and airborne soil etc.
Just use 1/2 strength, (or weaker)avoid applications in full sun or fast drying conditions.
I use 3 gallon backpack sprayer on all orchids, cycads, bromeliads, ferns, large leaved tropicals etc etc and anything that looks like it needs a boost, cactii as well, salvias get some if I think they are anemic.
Siebert suggested(when he saw my patch) that growing them in the same area, year after year may lead to weakened vigour, (I suspected this, and with a heavy nitrogen feeder, its too be expected)
and I may have run into that limit last year, with weak flowers and no seed set... so I'm throwing stuff at them this year....ferts,(chemical and organic) sifted composts, anything extra lying around

The Patch has probably pumped out 15-20 lbs of stems and leaf, so soil is getting a bit tired, despite me adding things over the years...but digging up patch and re-doing is not really an option....so I'm going for the super top dressing method....I had slcaked off for awhile, as you end up burying plants in order to work materials down into soil (wheelbarrows full) and I was afraid of losing the "next" haha Luna....but I'm over that, just need to get the whole thing strong again.