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Grow lights drying top 1' of soil. Not absorbing water.

Posted by Jayinjay2424 (My Page) on
Sat, May 5, 12 at 5:14

Started growing several varieties of vegetables from seed indoors in 144 1" seed trays. Everything is going well. I transplanted to 3" pots. Growing under 12 4' t5HO lights. The lights are about 4" from the tops of plants.

Im down to watering (depending on variety) thoroughly every 5 days. However, the last time I watered, I noticed all the water just ran down the side of the pots and out the bottom. the top 1" of soil has become hardened and crusty and the soil around the edge of the pot has "shrunk" a fraction of an inch. I think the heat from the lights caused the top to get crusty. And the sides shrunk because of slight soil compaction. Thus,true soil isn't absorbing the water and the plant look a little droopy (like they normally would when lacking water)

One other interesting note, I am using clear plastic cups and can see the roots coming down the sides of the pots, I think more so than normal because that is where the water is.

Have other people had this problem? Suggestions?

Also, my first thought was mulching. Suggestions for mulches for indoor 3" pots under grow lights?

Thanks!


Follow-Up Postings:

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RE: Grow lights drying top 1' of soil. Not absorbing water.

What media are you growing in?
Mixes with too much peat are prone to drying out and then repelling water. Is there a way to water your plants from the bottom? Like set them in a tray of water and let them absorb it and then remove the tray?
Sometimes that is the best way to rehydrate dried out peat.


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RE: Grow lights drying top 1' of soil. Not absorbing water.

They are in 3" plastic cups. In the seed starter trays, I used seed starting mix and then when I potted up to 3", I used a typical organic potting soil. Watering from the bottom isn't really an option... I have about 150 plants that just barely fit under the lights. Moving them twice a week to water from the bottom would be too time consuming and I haven't been able to find a plastic bin or tray suitable for holding them, that wouldn't take up too much space where they would still fit under the lights.

Also, a semi seperate question, I was thinking of adding some compost to the pots but was wondering if it could or would burn the seedling stems if in direct contact. Also, I thought it might be less prone to drying out.

I want to note, it's only the top inch drying out completely. The soil underneath seems normal but getting the water to it is difficult.


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RE: Grow lights drying top 1' of soil. Not absorbing water.

  • Posted by zenman Ottawa KS 5b (My Page) on
    Sun, May 13, 12 at 10:59

Hi Jayinjay,

"Watering from the bottom isn't really an option... I have about 150 plants that just barely fit under the lights. Moving them twice a week to water from the bottom would be too time consuming and I haven't been able to find a plastic bin or tray suitable for holding them, that wouldn't take up too much space where they would still fit under the lights."

I think the advantages of watering from the bottom would justify the effort of finding some trays. I have used my PermaNest trays for many years.

I have also used some cookie sheets that I got from Walmart as trays. The cookie sheets can act as shallow trays. The cookie sheets add maybe a quarter of an inch of elevation, while the PermaNest trays add maybe a half an inch. It is vastly easier to flood a tray and simultaneously water all the pots in it than to try to water the pots individually. And if your shelf is reasonably level, you can add the water to the tray from the front without moving anything. Good growing mediums will "wick up" the water all the way from the bottom to the top. I use Premier ProMix BX.

ZM
(not associated with any product or vendor mentioned)


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RE: Grow lights drying top 1' of soil. Not absorbing water.

I encountered this as well. Though I do only use backyard soil and place it on plastic cups. I use led lights. I tend to water the seedlings immediately prior to placing them under the lights via bottom up technique. Then mist the surface right before I got to bed then immediately upon waking up. Honestly some of my seedling dies because the surface became crusty.


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RE: Grow lights drying top 1' of soil. Not absorbing water.

sammyyummy- use a potting mix- yard soil is too heavy for potted plants. You'd be amazed how much better things will do in a better mix.


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RE: Grow lights drying top 1' of soil. Not absorbing water.

Yep too little drainage! I personally use a potting mix by Fafard (3BC), which is a pretty custom mix I can get my hands on from a local greenhouse. Basically:

Canadian Sphagnum Peat Moss (50-60%)
Processed Pine Bark (25-30%)
Perlite (10%)
Vermiculite (10%)


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