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What are the optimum NPK levels in soil?

  • by dosboot
  • Mar 11 2009 12:55 AM
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Posted 11 March 2009 - 12:55 AM

I know that this info is some where, but I can't find it. Kind of tired, so maybe that's it.

Anyway, I was wondering what the optimum levels of nitrogen, potash, and phosphorus in the soil (not in fertilizer or nutes) is for cannabis?

Thanks. :)
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  • You can call me Billy

  • BtBR
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Posted 11 March 2009 - 01:02 AM

The plant has different needs for vegging than for flowering. And... the nutes you give it by ferting it and the nutes it gets from the soil, I don't think the plant can really tell the difference.

20-10-10 for veg
10-20-20 for flower

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Posted 11 March 2009 - 01:06 AM

The plant has different needs for vegging than for flowering. And... the nutes you give it by ferting it and the nutes it gets from the soil, I don't think the plant can really tell the difference.

20-10-10 for veg
10-20-20 for flower


Hi BtBR. :)

So, if I used a rapitest soil test kit, it would measure the NPK levels on the same scale that you refer to? I really don't know.

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Posted 11 March 2009 - 01:13 AM

Hi BtBR. :)

So, if I used a rapitest soil test kit, it would measure the NPK levels on the same scale that you refer to? I really don't know.


Sorry I don't know anything about soil test kits

Grandpa's grow guide has recommendations for NPK ratios, doesn't mention soil testing though.

Earlier by "20-10-10" I meant ratio 20N-10P-10K
Grandpa recommends 10-60-30 or 10-30-20 for flowering

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Posted 11 March 2009 - 03:39 AM

Sorry I don't know anything about soil test kits

Grandpa's grow guide has recommendations for NPK ratios, doesn't mention soil testing though.

Earlier by "20-10-10" I meant ratio 20N-10P-10K
Grandpa recommends 10-60-30 or 10-30-20 for flowering


Thanks. Good info.

:)

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  • toastybiz
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Posted 11 March 2009 - 02:28 PM

I don't know if you can back out a NPK ratio from your soil, not with a Rapitest kit anyway. And if you could, the numbers would be nowhere near 20-10-10 or 10-30-20, When you buy soil that has any nutrients in it you will notice that the NPK is more like .05-.01-.01.

The NPK numbers are percentages of the material being measured that are each nutrient. So you certainly don't want to be growing in a medium that is 20% nitrogen, 10% phosphorous, and 10% potassium, that would be like trying to grow directly in fertilizer. Ferts are dliuted and then added to the soil, such that the percentage of the soil that is now composed of available N,P and K is a very low percentage.

The key in looking at NPK numbers is the ratio, not the absolute numbers.

To test the nutes in your soil you are better off with something like a TDS meter.

Edited by toastybiz, 11 March 2009 - 02:29 PM.


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Posted 14 April 2010 - 11:51 PM

this is some real good shit thanks. but I have a few questions and was wondering if you could email me directly suxidkush@gmail.com .
my question is I dont directly understand the soil mix maybe if you could explain it to me ( soil ) I get the npk levels but I'm having a hard time understanding all the other trace elements that the plants need and and if I use a mix involving perlite and vermiculite will it delute the mix and lower the ph of the soil also is asbestos harmful to the plant cuz I have read that vermiculite contains asbestos. also how often should I use liquid bloom?? for the flowering. also I have caliche everywhere was wondering if I can grind it up and use it as a clay I know it would also drop the ph but id use a meter and get it back up I was just wondering if there is anything in caliche that would be harmful? I mean you may not know all this cuz you obviously may not live in nevada but I'm just starting and studying hardcore. also I'm gonna take a risk and use leds.. no heat low wattage.. :hello: also um I had a really important q so if you could get back to me ill remember lol.. too mush good buds.. wait wat am i saying.


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