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Lately, I've been getting poor germination of seeds. I seed into net pots on a tray with a 2/3 coir and 1/3 vermiculite mix and water daily from my aquaponics fish tank. The seedling tray are under lights and watered once per day. I get good germination but after a few days, they just fizzle out and never get past their first set of leaves. I have plenty of nitrate in my tank for my mature lettuce but does the coir/vermiculite mix and occasional water from the aquaponics system provide enough nutrients to get the plants started? Should I be mixing in worm castings into the mix? Adding compost tea to my watering? Any thoughts? Does anyone else have problems getting through the early plant stage?

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what is the localised humidity directly under the lights? exactly where the plants are. it could be low humidity if the lights are drying the air too much, also do you need to water every day? if they are drying out that quick with seedlings then it suggests to me its either too hot or too dry there or more likely a combination of the two, either that or you are overwatering when they havent used up whats in the pot already and its causing damping off. 

 

seedlings need very little in terms of nutrients until they get a few sets of proper leaves, the tea could help provided its not loaded with nutes and i normally wait until mine are established before using any.

 

when they fizzle out do they die from the top? as in the leaves go first or does the stem go near the base of the seedling?

I agree with Ian, sounds like it might be "damping off" which is a condition caused by too much moisture/humidity. Do you have a fan for air circulation? That can help and the other action to take is water less. But air circulation is probable the best thing you can do to avoid this problem. BTW, damping off is characterized by the stem of the plant becoming shriveled just where it emerges from the soil mix and it typically strikes after the first two seed leaves are fully extended but before true leaves grow.

Adding something like perlite to the mix certainly wouldn't hurt, particulary if it is damping off disease. Vermiculite is used for it's water retaining properties, so is coir (mainly). This is why people add an equal amount of perlite, as it does not retain water it's job is to 'retain' oxygen in the air water mix of things. Your potting medium may just be too damp.

That is why most 'formulas' call for 1/3 vermiculite, 1/3 perlite, 1/3 coir (or sphagnum moss). Adding worm castings will do nothing to help the air to water ratio. And as Ian alluded to, seedlings have all the nutes they need from what is contained in the seed itself until they get to working on a couple of sets of true leaves.

If I had to assume anything I would say that your A/C system is destroying your seedlings by drying out the root systems before they even develop. 

The reason I say this is because that picture shows me a seed tray, no visible plants, no damaged plants, no cover, no noticeable moisture indicated by what is lying outside the seed cups and what looks like sheet rock in the background which I assume is a temperature controlled room. 

A/C systems cool by "dehumidifying" and "drying" the air while reducing the temperature of the environment including your seedlings. It's so intense that one day they will be looking good and the next day they are wilted and falling over. So my best guess with what you have stated and what I've seen is that you should just put a cover over them to keep them from drying out. You could also be out of phase for seeding/planting but I think the A/C is your biggest problem just from looking at the picture you posted. Hope this helps.

Thanks for all the advice. Perhaps I was watering too much given my coir/vermiculite mix. I was just concerned they wouldn't have enough nutrients at that early stage. I guess the fact that I'm using an inert media made me think they needed more nutrients, hence, adding more fish tank water. 

I've started a compost tea blend using 1/2 gallon aquarium water, 1/4 cup worm castings, 1/4 capful of Maxicrop, and a dash of agave syrup. I'll add a little of this to my aquarium water I pull out for watering starts and hope it gives a little extra nutrient kick for a less frequent watering schedule (and all the nutrients they need).

I do live very close to the coast and our local environment is generally high humidity so this may be what allows me to have seedlings without a seedling tray cover. No A/C for me with our location and I'll try to just keep a more careful eye on my starts to let them dry out a bit first before the next watering. Thanks everyone!  


Vlad Jovanovic said:

Adding something like perlite to the mix certainly wouldn't hurt, particulary if it is damping off disease. Vermiculite is used for it's water retaining properties, so is coir (mainly). This is why people add an equal amount of perlite, as it does not retain water it's job is to 'retain' oxygen in the air water mix of things. Your potting medium may just be too damp.

That is why most 'formulas' call for 1/3 vermiculite, 1/3 perlite, 1/3 coir (or sphagnum moss). Adding worm castings will do nothing to help the air to water ratio. And as Ian alluded to, seedlings have all the nutes they need from what is contained in the seed itself until they get to working on a couple of sets of true leaves.

When you first start seeds, they really don't need any nutrient in the water.  Generally they don't need nutrient till the first true leaves start to appear and then only weak.

I've heard of misting the plants daily with cooled off weak chamomile tea to defend against damping off.  I expect an aerated worm tea blend diluted, strained and sprayed on the seedlings might work too but I've never tried it.

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