PTGC NonToppers: Canna Cheese and Mega Crop
so i'm considering picking up 2 autopots because handwatering NFTG with all those bottles was a bit much on the last run. i think i might need a different cal mag to leave it in a reservoir though. i ran the rain science bags last time but i had a tough time keeping the humidity down so i am considering just running larger nursery pots and handwatering from a 5gal bucket of solution. probably 7 or 10 gal pots for flower
the speedy sprouter is showing more browning/brown spots on the tips of the first true leaves and it is now appearing on the second set. the other seedling is looking good. i have also noticed some slight irregular growth that looks like calcium deficiency as well.
fed at 450ppm swapping demeters for generic cal carbonate. so 150ppm of cal carb and mag amped and 2.1g megacrop. ph at 6.3
my big boi is showing more brown 🙁 but both are still growing quickly, love being able to see 12hrs worth of growth, just crazy! swapped the morning feed for cal and mag products, demeters, herc, mag amped, at a lower ppm but no megacrop this round, IN: 390ppm OUT: 500ppm. been continuing the foliar sprays as well with each feeding
Follow up on the deficiency - it's resolved after adding 100ppm calcium and 50ppm magnesium to the feed (I am using RO). I dialed the megacrop back to 1.6g so i've been sitting at around 420ppm 😉 for a couple days and have seen good clean growth. The one showing the browning first leaf set had just a spot or two on the tips of the second node, as well as a little cal def ripple on each leaf, and the third node is looking good.
I transplanted them from their 16oz fabric bags to my 1/2 gal ez swap pots last night. I also pulled the trigger on a 2 pot Autopot system, so I will transplant them again once near that 6 node mark. I remember last run it seemed like I was a bit early on the second transplant and one went into flower pretty quick afterwards as the medium didn't hold together as well as it would have if better colonized by roots.
i've got the lights on 24/0 and have been slowly dialing it up. i'm at about 300umol now that they're on 3 nodes. I will continue to increase it slightly, but the big question in all of the grow light material on this site is how does light intensity apply to autoflowers and light cycles? For me, the connection is DLI, but it isn't mentioned. My last plants got stressed in many ways, but they didn't tolerate the amount of light I tried to give them. It could have been in part from not increasing the light intensity in gradual enough steps, but I tried to go up to 950umol in early flower and slowly kept backing it down to about 350umol by the end of flower because they were stressing.
According to the info I've found about DLI, 30 mol/m2*day is a number that has been thrown out for tomato-like crops. If you look at a map of outdoor DLI, the maximum in the US is 60-65 mol/m2*day in CA in July, but could be as low as 30 by harvest time in September or October.
I attached one chart I found online for cannabis regarding DLI, but it is for photoperiods. If you take the 18/6 light schedule and extrapolate the peak in veg at 45 mol/m2*day, you do indeed get 700 umol. The peak in bloom at about 38 mol/m2*day on a 12/12 schedule puts intensity at 879 umol. So that chart is in agreement with the Chandra study regarding intensity, but of course the environmental variables will define the optimum intensity and DLI.
As for how this relates to autoflowers, to achieve 45 mol/m2*day at 24/0, I would need the light intensity to be just 520umol, and my current 300umol at 24/0 produces a DLI of 26, so it seems I am well on my way.
My 2x4 tent is in a closet that I leave the door ajar for air exchange, so I shouldn't be limiting CO2 beyond standard atmospheric limitations, but temperature might be where I was limiting growth previously. I was having a hard time with airpots and managing humidity without keeping a dehumidifier in the closet. (my 70pt is way too loud to be that close to my bed). The ambient temp in the tent is 75-79F and humidity has been around 65rh, but the airflow brings the leaf surface temp down to 71-72F. Since I'm running Bridgelux strip lights at very low currents, I think this could be my bottleneck. This time I am keeping the light all the way at the top of the tent and have it up to about 200W to try to bring the temp up, but I'm still at a 4-5F difference from leaf surface temp to ambient temp. which is the highest delta I've seen on any VPD chart. On the last run, once humidity started increasing, i had the fans on max and saw an even higher deficit. I think it was 78F in the tent and leaf surface temp was 68F. Seeing the research about bringing the leaf surface temp up into the 80's for LEDs because of less IR than HPS, etc. seems like a challenge when you consider all the airflow. I don't think it makes sense to put a heater in there to bring the room up to 90F to get a leaf temp of 85F.
So long story short, the girls are transplanted and happy and i'll keep you posted.