Sometimes when you experiment you fail, and learn from it. It's painful but most good lessons are, somewhat painful.
In this case, my first four trays that I added a little kelp meal to, have developed a fungal issue. Only those four trays, and kelp meal was the only difference.
I've turned on the lights over it and removed all humidity domes (don't really need them anyway) from remaining trays to try to avoid the issue on the rest.
I also believe I pinned down the germination rate problem on the mixed test trays to the heat of the HO lights. I noticed on a tomato tray that I had zero germination on the innermost cells. This led to the question of "why?" I did some more detailed soil temp tests today and found the high output T5's were heating the inner most portion of the trays to 100-102F. Between 95F and 105F germination rates on just about every vegetable on earth drops to zero. This is an issue on all 6 of the initial mixed variety test trays, with the outermost tray (#1) on the edge of the light having the best germination.
Unfortunately that kind of spoils the sprouting results, since the leftmost tray was staying 5 degrees cooler than the other two in each batch. Germination rates on the #1 trays of each batch were ~50% - not good. Germination rates on the other two trays were <25%, which is pretty horrible. The heat explains that, however. The tomato tray was the "canary" that clued me in on the issue. The pepper trays weren't showing the same pattern that the tomatoes were, but with 68 varieties and such widely staggered germination times on them, I wouldn't have picked out any discernible pattern.
Worth noting my tomato trays have now begun sprouting in the part that was "overheated" - so I doubt I've killed the pepper seeds; but rather whatever mechanism gets the seeds to start doing their thing wasn't happening at those higher temps.
I will cut lighting in half on new partially sprouted trays to avoid cooking them.
I'd like to see 80%+ germination rates (ideally 90%+) for the farm in future years. At the rate I'm getting now the plant out will be substantially scaled back from the goal.
I'll still be able to get some useful data, just not as much as I'd hoped. This wouldn't be an issue on same-variety trays (which is the bulk of the grow) - just those mixed trays where seedlings might emerge 2 weeks apart; I have to give the new seedlings light; but also have to keep the soil moist for those seeds still waiting to germinate...
In hindsight I should have just done complete trays of same-variety for the experiments, which is what I'm doing on the remainder of this year's 64 tray experiment (4608 pepper seeds).
If that fungus on trays 11-14 isn't gone by tonight after they've aired out some under 50% T5 light, I'm going to hit those four with a weak dose of H2O2 spray to kill it off.
Edited by TrentL, 12 February 2018 - 12:39 PM.