I forgot about the other thread I posted similar to this. I need to calibrate and see but it's probably low volumes on my permagreen. How about a liquid iron product at 3 oz/K that would be about 96oz in 7 gallons of water. That doesn't sound too difficult.
Most labels that recommend 2 gal water rates are for soil drench. 1 gal rates are foliar. I need to calibrate and experiment I guess.