Rahz
Well-Known Member
I've been slipping some observations into other threads because they didn't seem to warrant their own topic. Thought I would start a thread for those things.
First item, 3000K 70CRI beside 2700K 90CRI. Both samples exhibit a lot of vertical stretch along with overall plant size being notably larger. The primary differences between this grow and the previous grow with 3000K 70CRI:
Nutrient strength: previous grow was 10 gallon (1 gallon per square foot of canopy space). This one is 20 gallon (2 gallons-sq/ft). In both cases reservoir was/is topped off daily with full strength solution. Because of the extra volume it seems reasonable that the overall TDS remains higher in the 20 gallon system. Possible solution for boosting TDS levels throughout the week in the smaller system would be to top off with a stronger mix than the initial level. Because TDS readings can be somewhat unreliable after the changeout I've been hesitant to do this, but it may warrant some testing.
Reservoir size and circulation: Again, comparing the system volume, the 10 gallon system uses 3 5gallon buckets (2 plants + gravity fed rez). Root ball is restricted to about 3.5 gallons. With the 20 gallon system I'm using a 30 gallon tub. Each plant has about 10 gallons of space for the root ball and about 2-3 x the footprint. In addition it's a RDWC so better water movement through the root system along with more space for the roots to spread out.
Just a guess but between those two items I suspect the extra space and water movement has more to do with the observed differences than TDS. Yield with the 10 gallon system was fairly dense, best yield per foot yet. Whether the larger rez will support higher yield remains to be seen... more plant mass doesn't necessarily mean more yield. But, it would allow a shorter veg period. This was a 24 day veg (final plant footprint is 28"x28") and all other things being equal I could easily have knocked off a week, assuming I got the same stretch after 12/12. Another tricky proposition because less veg time means starting 12/12 with a smaller root ball.
Takeaways:
At start of 12/12 2700K 90CRI was taller, but not by nearly as much as I would have predicted.
In both instances we have very healthy plants, both under 3000K 70CRI. Stretch and plant mass notably higher with the larger rez. Suggests size of root ball is at least as much a determinant of potential stretch as light source. Plant height can be limited by using less solution per square foot, OR possibly supporting shorter veg times via more solution per square foot.
Anyway, these plants are going hog wild. I wouldn't be surprised if yield is slightly higher, but would be surprised if it was substantially higher. If you want to grow giant plants, or perhaps shorten veg time it would be good to experiment by ditching the grow buckets and try tubs... and/or a recirculating system provides obvious benefits in regard to nutrient uptake.
Finally, there could be some discussion about getting a similar effect with less volume via shallow water culture (3.5 gallons spread out over several square feet rather than being confined to a 3.5 gallon bucket. SWC is generally used for SOG, but I don't see why it wouldn't work with fewer, larger plants.
Not exactly scientific, and nothing new really, just wanted to draw attention to the importance of the water culture design and it's effect on growth rate. It's not all about the lights.
In other news, the 3500K 80CRI vs 3000K 90CRI challenge is happening in the bubble buckets. High CRI has a 5-8" jump on the 80CRI lamp, week 2 of 12/12. Hard to tell exactly because they're being trained on a screen. Previous test was 3500K 80CRI vs 3000K 70CRI, final yield of the two was almost exactly equal. Will the mighty 3000K 90CRI lamp be able to edge out the time tested 3500K 80CRI lamp? Or will yield results again be similar?
Takeaway: Worth mentioning here, when utilizing a SCROG method, higher CRI should support shorter veg times as that extra vertical growth can translate into extra width as the plants are trained. Put it all together and the shortest veg time for SCROG should happen with high CRI and oversized recirculating rez. Whether this translates into same yield with shorter veg time is TBD. In a couple months I'll put both of my 90CRI lamps over the 20 gallon system and test this out, flipping to 12/12 at 14 days regardless of whether I think they're ready.
First item, 3000K 70CRI beside 2700K 90CRI. Both samples exhibit a lot of vertical stretch along with overall plant size being notably larger. The primary differences between this grow and the previous grow with 3000K 70CRI:
Nutrient strength: previous grow was 10 gallon (1 gallon per square foot of canopy space). This one is 20 gallon (2 gallons-sq/ft). In both cases reservoir was/is topped off daily with full strength solution. Because of the extra volume it seems reasonable that the overall TDS remains higher in the 20 gallon system. Possible solution for boosting TDS levels throughout the week in the smaller system would be to top off with a stronger mix than the initial level. Because TDS readings can be somewhat unreliable after the changeout I've been hesitant to do this, but it may warrant some testing.
Reservoir size and circulation: Again, comparing the system volume, the 10 gallon system uses 3 5gallon buckets (2 plants + gravity fed rez). Root ball is restricted to about 3.5 gallons. With the 20 gallon system I'm using a 30 gallon tub. Each plant has about 10 gallons of space for the root ball and about 2-3 x the footprint. In addition it's a RDWC so better water movement through the root system along with more space for the roots to spread out.
Just a guess but between those two items I suspect the extra space and water movement has more to do with the observed differences than TDS. Yield with the 10 gallon system was fairly dense, best yield per foot yet. Whether the larger rez will support higher yield remains to be seen... more plant mass doesn't necessarily mean more yield. But, it would allow a shorter veg period. This was a 24 day veg (final plant footprint is 28"x28") and all other things being equal I could easily have knocked off a week, assuming I got the same stretch after 12/12. Another tricky proposition because less veg time means starting 12/12 with a smaller root ball.
Takeaways:
At start of 12/12 2700K 90CRI was taller, but not by nearly as much as I would have predicted.
In both instances we have very healthy plants, both under 3000K 70CRI. Stretch and plant mass notably higher with the larger rez. Suggests size of root ball is at least as much a determinant of potential stretch as light source. Plant height can be limited by using less solution per square foot, OR possibly supporting shorter veg times via more solution per square foot.
Anyway, these plants are going hog wild. I wouldn't be surprised if yield is slightly higher, but would be surprised if it was substantially higher. If you want to grow giant plants, or perhaps shorten veg time it would be good to experiment by ditching the grow buckets and try tubs... and/or a recirculating system provides obvious benefits in regard to nutrient uptake.
Finally, there could be some discussion about getting a similar effect with less volume via shallow water culture (3.5 gallons spread out over several square feet rather than being confined to a 3.5 gallon bucket. SWC is generally used for SOG, but I don't see why it wouldn't work with fewer, larger plants.
Not exactly scientific, and nothing new really, just wanted to draw attention to the importance of the water culture design and it's effect on growth rate. It's not all about the lights.
In other news, the 3500K 80CRI vs 3000K 90CRI challenge is happening in the bubble buckets. High CRI has a 5-8" jump on the 80CRI lamp, week 2 of 12/12. Hard to tell exactly because they're being trained on a screen. Previous test was 3500K 80CRI vs 3000K 70CRI, final yield of the two was almost exactly equal. Will the mighty 3000K 90CRI lamp be able to edge out the time tested 3500K 80CRI lamp? Or will yield results again be similar?
Takeaway: Worth mentioning here, when utilizing a SCROG method, higher CRI should support shorter veg times as that extra vertical growth can translate into extra width as the plants are trained. Put it all together and the shortest veg time for SCROG should happen with high CRI and oversized recirculating rez. Whether this translates into same yield with shorter veg time is TBD. In a couple months I'll put both of my 90CRI lamps over the 20 gallon system and test this out, flipping to 12/12 at 14 days regardless of whether I think they're ready.
