TheGreatSouthern
Well-Known Member
Hey guys.
I'm having some issues with my flood and drain garden at the moment.
The strange thing is it's happened the last two cycles in a row, but never happened in the many cycles before that, and isn't happening to another flood and drain table which is fed from the same nutrient tank.
The seedlings look perfect when planted, but a week later look like the photos. I've always grown it in a SOG between 49 plants per sqm and 64 plants per sqm.
They seem to survive their life cycle and flower ok, albeit with reduced quality and reduced yield. Yield is down by about 20%.
Strain is an F2 taken from Critical Kush Autoflowering/Mendo Mass Autoflowering parents. I never had this problem with the original strains or the F1, or the F2 of which I have run 3 cycles now.
There is a mild infestation of fungus gnats and a mild infestation of thrips, however these pests have been around for ages, are under control as far as is practicable, I can't seem to eliminated them due to the open nature of the setup and they have never caused these problems in previous cycles and aren't causing problems with the other flood and drain table.
Brand of nutrients is Nutrifield (Australian brand I think)
EC is 1.6-1.8. That may seem way high for seedlings, and to me as the layperson the problems with these seedlings look more like google search images of nute burn than anything else, but I've always run it that way and they have always loved it. This strain finishes from germination in 9 weeks like clockwork and normally yields about 3 grams per watt in that time running lights 24 hours, they feed like crazy.
PH varies. I run an 1100 litre (290 gallon) reservoir and PH it down to 5.3-5.4 and it naturally rises to 6.5 over the course of 5 days. I dump the whole thing, flush the tables and refresh it every 2 weeks approx. This has worked flawlessly since it was set up two years ago.
The flood and drain tables are 500 litres each (made from half IBCs) and contain a mix of clay pebbles, perlite and vermiculite. They take turns flooding each hour and flood seven times per day. they take about 20 mins to drain back to the res.
I have tried flooding the problem tables right up to the top and PH testing the solution - it is the same PH as the res every time.
I haven't refreshed the media for a long time. I found the overall quality of the grow improved every cycle if I left the roots in there after harvest, planted new seedlings, added a beneficial bacteria mix and left it to do its thing naturally, so possibly this may have something to do with the problem? hopefully someone has experienced this and can chime in? It seems unlikely to me as the media in the problem tables is younger than the media in the tables with no problems.
I can't really even figure out what if any deficiency the seedlings are experiencing here. I look at the charts and it sort of looks like a mix of a few problems.
One thing I can think of as a possible issue is that the tables having the problem are significantly lower than the ones not having any problems and it is possible some nutrient solution is staying in the bottom of these tables. It seems unlikely that this would cause root rot though as it is still being flooded with about 300 litres of fresh solution every 2 hours all day, so any nutrient pooling in the bottom should be getting exchanged and the oxygenation should be as high as possible with this method, at least to my mind.
The best guess I can really have at this is it's a combination of nute burn and thrip damage. when you zoom the photos you can see there are quite a few of the little shits sucking away on the leaves.
One thing I've learned the hard way with these fast autos is you have to get onto such problems the moment you spot them, so what I'm going to do right now is spray the thrips, dump nutes, flush and leave the flush water in the tank to keep flushing the tables for a couple days. hopefully somebody's going to be able to enlighten me a bit in the next 24 hours or so.
Any thoughts from the experts?
I'm having some issues with my flood and drain garden at the moment.
The strange thing is it's happened the last two cycles in a row, but never happened in the many cycles before that, and isn't happening to another flood and drain table which is fed from the same nutrient tank.
The seedlings look perfect when planted, but a week later look like the photos. I've always grown it in a SOG between 49 plants per sqm and 64 plants per sqm.
They seem to survive their life cycle and flower ok, albeit with reduced quality and reduced yield. Yield is down by about 20%.
Strain is an F2 taken from Critical Kush Autoflowering/Mendo Mass Autoflowering parents. I never had this problem with the original strains or the F1, or the F2 of which I have run 3 cycles now.
There is a mild infestation of fungus gnats and a mild infestation of thrips, however these pests have been around for ages, are under control as far as is practicable, I can't seem to eliminated them due to the open nature of the setup and they have never caused these problems in previous cycles and aren't causing problems with the other flood and drain table.
Brand of nutrients is Nutrifield (Australian brand I think)
EC is 1.6-1.8. That may seem way high for seedlings, and to me as the layperson the problems with these seedlings look more like google search images of nute burn than anything else, but I've always run it that way and they have always loved it. This strain finishes from germination in 9 weeks like clockwork and normally yields about 3 grams per watt in that time running lights 24 hours, they feed like crazy.
PH varies. I run an 1100 litre (290 gallon) reservoir and PH it down to 5.3-5.4 and it naturally rises to 6.5 over the course of 5 days. I dump the whole thing, flush the tables and refresh it every 2 weeks approx. This has worked flawlessly since it was set up two years ago.
The flood and drain tables are 500 litres each (made from half IBCs) and contain a mix of clay pebbles, perlite and vermiculite. They take turns flooding each hour and flood seven times per day. they take about 20 mins to drain back to the res.
I have tried flooding the problem tables right up to the top and PH testing the solution - it is the same PH as the res every time.
I haven't refreshed the media for a long time. I found the overall quality of the grow improved every cycle if I left the roots in there after harvest, planted new seedlings, added a beneficial bacteria mix and left it to do its thing naturally, so possibly this may have something to do with the problem? hopefully someone has experienced this and can chime in? It seems unlikely to me as the media in the problem tables is younger than the media in the tables with no problems.
I can't really even figure out what if any deficiency the seedlings are experiencing here. I look at the charts and it sort of looks like a mix of a few problems.
One thing I can think of as a possible issue is that the tables having the problem are significantly lower than the ones not having any problems and it is possible some nutrient solution is staying in the bottom of these tables. It seems unlikely that this would cause root rot though as it is still being flooded with about 300 litres of fresh solution every 2 hours all day, so any nutrient pooling in the bottom should be getting exchanged and the oxygenation should be as high as possible with this method, at least to my mind.
The best guess I can really have at this is it's a combination of nute burn and thrip damage. when you zoom the photos you can see there are quite a few of the little shits sucking away on the leaves.
One thing I've learned the hard way with these fast autos is you have to get onto such problems the moment you spot them, so what I'm going to do right now is spray the thrips, dump nutes, flush and leave the flush water in the tank to keep flushing the tables for a couple days. hopefully somebody's going to be able to enlighten me a bit in the next 24 hours or so.
Any thoughts from the experts?
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