First time grow: yield expectations

I'm a beginner with all this. My first batch (4*Grapefruit, 1*Critical #47) is only in the veg stage and though they seem to grow don't have the best of time.
Soil is Canna Terra, and I've been feeding the babies BioBizz Grow from week 2 onward. PH is managed by vinegar (it lacks a buffer and doesn't hold, and I suspect this contributes to any problems I might be experiencing) and in the way of lighting I have a generic 400w HPS which I use as a sole light source for this grow.
The plants I intend to veg until they are some one foot of height, and when they start to stretch they'll end up 2-3 feet, which is fine for Grapefruit.
The question is how much can I expect in yield from this starting point? Some would say hardly anything since this is my first grow, but then again, others have got as much as 44 grams per plant.

It depends mostly of how healthy they are and then to a lesser degree amount and quality of light, how long they are vegged and size of plants, genetics for strain, proper nutrient levels within pH range, letting them flower long enough, size of pots, method of grow.... get the idea yet? The biggest impact a grower can have for a heavy harvest is grow a healthy plant in every way.

If they are healthy, under a 400- 5 plants I'm guessing 5-6 oz, give or take a oz.

If they haven't been grown well and have experienced problems, maybe 2-3 oz.

7 oz I'm being told is the standard for a grower with any experience, which would boil down to 0.5g/w. Another beginner ended up with 0.17g/w, which would be close to your minimum. Would just barely work with me, but then again, a baby would stagger a lot before it would walk on its own. One of my concerns is how I'll be able to clone when I'm barely able to bring up a decent crop, since cloning will reduce the quality of the plants.

with 400 watt hps at 50 watts per plant 7250 lumens for plants. You should be able to grow 8 plants. If they where 2 feet I would say they would yeild 18.66 grams each. That would give you 5 ounces.

SSHZ said:

It depends mostly of how healthy they are and then to a lesser degree amount and quality of light, how long they are vegged and size of plants, genetics for strain, proper nutrient levels within pH range, letting them flower long enough, size of pots, method of grow.... get the idea yet? The biggest impact a grower can have for a heavy harvest is grow a healthy plant in every way.

If they are healthy, under a 400- 5 plants I'm guessing 5-6 oz, give or take a oz.

If they haven't been grown well and have experienced problems, maybe 2-3 oz.

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I agree. You should be able to get atleast an ounce off each plant. And that's a conservative estimate.

Subliminator said:

with 400 watt hps at 50 watts per plant 7250 lumens for plants. You should be able to grow 8 plants. If they where 2 feet I would say they would yeild 18.66 grams each. That would give you 5 ounces.

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Where did you come up with these numbers?

I would say 3-4 plants max under a 400 watt (unless it is SoG 12/12 from seed) and you should look at around 2 oz per plant.

I agree. Flowering plants at 1 foot tall, you probably shouldn't have more then 4 plants under a 400 watt bulb. Or 6 plants for a 600 watter. But keep them short or your lower buds will be crap.