Als Mix and PH?

17 years ago

Trying to get a head start on the growing season I started some plants indoors.

I mixed my first batch of AlÂs mix and I repotted a 6 pack of tomatoes into 4" containers and have had them under first a 400 watt HPS light and now florescent lights.

The poor little buggers are dieing. At first they were doing quite well, but now a few arenÂt much more than 6" sticks. After a few days under the HPS the crowns of most started to turn yellow. Thinking that I burned them with to much light and heat I moved them farther away. The yellowing slowed, but it didnÂt stop.

I had been spraying them daily with a weak fertilizer solution. I think I over watered and over fertilized them. IÂve since stopped fertilizing and watering all together. I only water now with plain water and only wnen needed, New small plants I start from seed are OK at first, but anything more than 3" tall starts to turn yellow and die. Basil on the other hand is thriving.

IÂm beginning to think that besides the over watering and over fertilization that there is still something else wrong. Could it be the soil ph? The mix I made was the 511. I couldnÂt find pine bark fines, so I substituted some small pine bark and supplemented that with composted redwood fines.

I think the problem now could be either a ph issue or that the redwood fines were treated with nitrogen. Do I need to throw everything away and start over?

Andy.

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Comments (3)

justaguy2
17 years ago
Did you add lime? The pH of the pine bark and peat are around 4-5 which is quite low. That could be a problem.

I am not sure the impact of the redwood fines. Unless they were really composted they could be limiting the nitrogen the seedlings can get which could explain why they do fine while until larger.

Spraying them daily with fertilizer (foliar feeding?) is a mistake, particularly if the spray contained NPK.

I am not really certain what the exact problem is, but if there is time I would put the current batch of plants to one side and stop fertilizing them.

I would then start another batch. If you don't have suitable ingredients on hand then get a bag of MG potting mix and use that. Don't fertilize at all until there are true leaves and then fert once at 1/4 strength. Wait at least 2 weeks before doing this again.

I am using 50% pine bark fines and 50% Turface MVP for starting all my seeds including tomatos and there are no problems. Oh, and I am using a 400W HPS light as well so it's not that unless you have it too close to the plants.
tokapeba
Original Author
17 years ago
I followed the recipe and put in the 1 cup of dolomite for the batch. I didn't add any extra, I was waiting until I put them in their final container. The other day I did mix a little dolomiter in water and added a little to each pot.

I Planted a 6 pack of early girl last week, so they should pop any day now. The cucumbers I planted at the same time last week popped yesterday.

I'm going to leave them on the florescent for the rest of this year I have 2 lights, 1 with grow bulbs and 1 with full spectrum bulbs. I might try the HPS again next year, but I was thinking I should move to a Metal Halide instead.

Andy.
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justaguy2
17 years ago
When you say the crowns yellowed do you mean the lowest growth? If so that is usually a nitrogen deficiency. It could be lack of N, but it is also the result of a too soggy potting mix. Since you used composted redwood that could do it and it could also be tying up any N you add. Not 100% sure on the exact cause in your case.

Nevertheless since I used 50% pine bark and 50% Turface for seed starting I am confident it isn't the pine bark that is the source of troubles for you (since you limed it).

As far as the HPS light goes I agree MH would be a tad better for seed starting, but I have used mine for 6-7 years for the purpose. No problems. I have found that the growth rate of plants is affected by age of the bulb, but that would be true with MH as well. Regardless of bulb age plants wouldn't yellow and die from it.

I am certainly not telling you to not switch to MH if you choose to, just that HPS is not the source of your problems.