I'm on my fourth season of doing peat soilless mix in grow bags with salt based fertigation.
The main thing I found for a strong grow is good EC management of the media.
I start with well established clones that are vegged indoors.
Plants are fed every watering, but the EC changes depending on weather.
In late April I'll feed at about 1.6EC. The temps are cool and sun is not too strong yet. Plants are drinking slowly at this point.
Later in May and June when temperatures are in the high 60's low 70's, I'll drop to 1.2EC. There is some evaporation from the bag and plants are drinking more now.
My last rez mix was 0.9EC in bright 90 degree weather. There will be considerable evaporation from the bag and plants are drinking at a very fast rate.
One off rain storms I continue normal feed next water.
Large storms I may supplement a strong feed.
Feeding in the rain. | Rollitup
To elaborate on what Jjgrow420 was saying, AN isn't exactly junk....it's just extremely cost inefficient.
The pH perfect market ploy may have some merit in something like a DWC grow, but you have 60 gallons of buffered media.
If you dump anything in the range of 5.5-6.5pH on it, the plant and media will take care of the rest.
Assuming you will be buying the larger 10/23L retail jugs, you still are at $10 per liter.
AN recommends about 15ml each of A+B per gallon for mature plants, so that would be about $15 to make a 55 gallon barrel.
How many 55 gallon rez barrels will you go through in a week?
Any of the big AG ferts will work just as well and cost around $1.00-$1.50 a barrel. Ya... it's not 100X cheaper, but over dozens of barrels throughout the season it would add up to some decent pocket change.