To answer the question of what commercial grow operations are using.
Id say 95%+ use a Gavita 1000w or similar with the DE Phillips bulbs. But has been stated.
You HAVE to have minimum of 36 inches from the top of the canopy, and are good for a 5 x 6 area vs 4 x 4 for a 1000w Hortilux HPS.
Hortilux in the right situation though is hard to beat.
I/me and my 2 cohorts of over 30 years grow large plants in large containers and up to 3 1000w Hortliux for Flowering, though I did just buy 2 1000w Gavitas and gave them to a buddy 3 weeks ago to experiment with, and within a week he already noticed a difference. I get all his product though.
At the moment he, and another buddy are growing a 3 years old Mr Nice Super Silver Haze F2 that was picked from over 100 females. It produces huge, stretches 4x 5 x in flowering, and has dense buds all the way down the branches. We don't trim off the lower secondaries, as they produce big. We wont keep a plant unless it has good complex secondary branching, as this is key to big production.
The plants are also Bent to grow laterally, and all secondary branching is trained to grow vertically, while the growing tip grows Horzontially. Secondaries get intensely blasted with light. It basically becomes a hedge, and you would have to get underneath the plant and look up, to find the growing tip when properly trained. I also NEVER TOP them. This stops the growing tip. Unless you want to give it 2 weeks to catch up?? IMHO in many instances, topping slows them down, and takes 10-14 days to get over it, and catch back up. So its 2 weeks lost IMHO when time is a concern.
Using 2 plants in 20 gallon containers, Promix BX per 1000w Hortilux we get at least 2 lbs per 4 x 4 ever 70 days
We/I also veg with a 1000w Hortilux HPS and 5 gallon containers, and transplant into 20 gallon the day of flip.
Feeding??
If using Chemical we ue.
Sunbulb Orchid food, and Cal/Mag supplement.
The make both a Veg, and Flowering formula, contains NO UREA NITROGEN ( Cheap ), and also contains some Magnesium
For seedlings I use
1/2 tsp Veg x 1/2 Tsp Bloom x 1 Tsp Cal/Mag per 5 gallons water. Feed every watering.
As they get bigger I go to 1 Tsp Veg x 1 Tsp Bloom per 5 G water. 1 Tsp Cal/Mag. Feed Water every time
Full Veg get 2 Tsp Veg x 1 Tsp Bloom per 5G water. 1 Tsp Cal Mag. Feed Water every time.
1st 10-14 days flowering will give Veg Formula.
15 days until Mid Bloom gets. This can also vary if it is a really long flowering variety. Slight changes are made with really early, or really long flowering varieties. This is for 50-75 days. You just have to determine lengths of early, mid, late, blooming cycle, and adjust accordingly.
Also some plants may have to be skipped 1 feeding every 3rd feeding, but from what Ive found, is rare. I just use light feedings. Often.
2 Tsp Bloom x 1 Tsp Veg x 1 Tsp Cal/Mag.
Late Bloom drops the 1 Tsp Veg.