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How to find the right dose of fertilizer

Los_Serpent

New member
I'm trying a new thing, I got tired of spending plenty of money on fertilizer. And bought a 15 7 15 fertilizer that has pretty much everything I need. It was not meant for weed so I don't know the dosages

I have a huge plant in a 18 liter bucket. It's granural fertilizer but I'm gonna dissolve it in water. How can I figure out dosage based on the fact that it is 15 7 15?
 

JJ Lowe

Active member
Do you have access to a ec/ppm meter? Just stay under 1000ppm for starters and you should be good.

Most powdered fertilizers are around 1 tsp per gallon.
 

aridbud

automeister
ICMag Donor
Veteran
If dissolving in water....maybe crush the granules as they don't dissolve easily. Granular fertilizer is meant to be slow long term over a few months period. Maybe 1- 1.5 TBS per 1 liter of water. Less is more. Try it at 1 fertilization watering followed by water only and see how plants react.
 

Los_Serpent

New member
If dissolving in water....maybe crush the granules as they don't dissolve easily. Granular fertilizer is meant to be slow long term over a few months period. Maybe 1- 1.5 TBS per 1 liter of water. Less is more. Try it at 1 fertilization watering followed by water only and see how plants react.

How long does it take to see if it's doing damage or if its good?
 

troutman

Seed Whore
I'll give you a tip. Use as little as possible and only increase as needed. It's better to underfed vs overfeed. :tiphat:

BTW: Usually there's dosage recommendation on a label on the container. If not Google the fertilizer brand online for more info.
 

Grapefruitroop

Active member
Granular in most cases means also coated for slow release.....those little blue balls generally...If so this may give u problem on the long run...crushin it it wont help i think...
Maybe you should get your hands on some "Soluble" all purpose nute similar to the one u have but explicitly called soluble...
Or also jack's or megacrop or yara:joint:


And yeah a EC pen is always your friend!
 
Last edited:

hyposomniac

Active member
15/7/15 converts to 15/3/12.5

Used at 1g (1000mg} per liter will give you:
N - 150mg (150ppm)
P - 30ppm
K - 125ppm

Does this fert have any Ca, Mg or micros?
 

Switcher56

Comfortably numb!
Granular in most cases means also coated for slow release.....those little blue balls generally...If so this may give u problem on the long run...crushin it it wont help i think...
Maybe you should get your hands on some "Soluble" all purpose nute similar to the one u have but explicitly called soluble...
Or also jack's or megacrop or yara:joint:

And yeah a EC pen is always your friend!
Wow! I have used plenty of blue granule fertilizers in my day. I never had a problem diluting them! ???
 

Switcher56

Comfortably numb!
15/7/15 converts to 15/3/12.5

Used at 1g (1000mg} per liter will give you:
N - 150mg (150ppm)
P - 30ppm
K - 125ppm

Does this fert have any Ca, Mg or micros?
I will open my wallet but, I'm not about to open my wallet with your math! (being facetious, is that Trump math?) You simply cannot apply a 'factor" to both P&K and not apply it to N. What king of math is that?

My reaction to the Q was reduce the recommended dosage by 1/3, to bring you in line to what we use. Then of course we have Cal/Mag and others. But...
 

growingcrazy

Well-known member
I will open my wallet but, I'm not about to open my wallet with your math! (being facetious, is that Trump math?) You simply cannot apply a 'factor" to both P&K and not apply it to N. What king of math is that?

My reaction to the Q was reduce the recommended dosage by 1/3, to bring you in line to what we use. Then of course we have Cal/Mag and others. But...


Label ( N, P2O5, K2O )
P = P2O5 x .44
K = K2O x .83


15-7-15

15

7 x .44 = 3.08

15 x .83 = 12.45


1 gram in 1 liter = 150 N 30.8 P 124.5 K


More math, Less bullshit.
 

Grapefruitroop

Active member
Wow! I have used plenty of blue granule fertilizers in my day. I never had a problem diluting them! ???
I think that the difference lays in the form of Nitrogen that they use...
If is Urea is gona be slow releasing...otherwise no.
Like MendoGrowMore is totally soluble but if you go to the hardware store you may find that the urea coated ones are common and not fully soluble cause they are meant to be spreand on the soil surface (for lawns or orchards) instead of mixed with water for fertirrigation...


Yara for ex. has two different granulated products one soluble and another slow releasing....
Never tried any of em....but i guess thats important to keep in mind.
:joint:
 

TanzanianMagic

Well-known member
Veteran
I'm trying a new thing, I got tired of spending plenty of money on fertilizer. And bought a 15 7 15 fertilizer that has pretty much everything I need. It was not meant for weed so I don't know the dosages

I have a huge plant in a 18 liter bucket. It's granural fertilizer but I'm gonna dissolve it in water. How can I figure out dosage based on the fact that it is 15 7 15?

1. This has way too much nitrogen, not enough phosphorus compared to potassium. If you're using solid and liquid nutrients it is best/essential to stick to nutrients and media meant for cannabis.

2. I am becoming a fan of complete fertilizers. So:

a) Use a supersoil

You can mix your own, as long as it has

N - blood meal, alfalfa meal/pellets
P - rock phosphate, bonemeal
K - vinasse, wood ash
Ca - magnesium lime, rock phosphate, bonemeal
Mg - epsom salt, maerl magnesium lime
Si - silica clay like Mineral Magic, Jersey Green Sand, etc.
S - epsom salt
Trace elements: lava meal, basalt meal, seaweed

Or you can buy ready made supersoil mixes. Or buy a heavily ferilized soil.

b) Make your own liquid nutrients

The best is to ferment cannabis parts - leaves, flowers - in sugar and water, with no air. Think of it as kombucha without the SCOBY.

Just use the leaves or flowers, reed sugar (any raw sugar because it has more nutrients) and cool water. The microbes on the plant are all you need for fermentation and what you're looking for because they're likely to be friendly to weed.

This is really effective, has everything cannabis needs in a liquid form, and has sugars in it which the microbes will used to further break down the nutrients in the supersoil.

You will need to use different parts of the plant for it's various stages - leaves from seedling through veg, flowers through flowering. Those can be cannabis flowers, hemp flowers, I'm using the flowering parts of stinging nettles right now.
 

hyposomniac

Active member
I will open my wallet but, I'm not about to open my wallet with your math! (being facetious, is that Trump math?) You simply cannot apply a 'factor" to both P&K and not apply it to N. What king of math is that?

My reaction to the Q was reduce the recommended dosage by 1/3, to bring you in line to what we use. Then of course we have Cal/Mag and others. But...


P = P2O5 x .43
K = K2O x .83
N = N
It's the kind of math you apply to fertilizer labels to get your elements.
And 1g/L is not a dosage recommendation, it's an easy way to find ppm and adjust from there.
Teach a man to fish..
If any of this is wrong, I'm open to suggestions.
 

Los_Serpent

New member
15/7/15 converts to 15/3/12.5

Used at 1g (1000mg} per liter will give you:
N - 150mg (150ppm)
P - 30ppm
K - 125ppm

Does this fert have any Ca, Mg or micros?

It has mg but is low in ca, but I've made my own calmag from eggshells, as well as a potassium fertilizer from bananas for flowering when I need more pk...

Thank you for those numbers, could you help. Me to understand them?

How much does a large sized weed need? 18l pot 2 weeks into flower? Any way to calculate that so I don't have to guess to much and lose valuable time
 

Los_Serpent

New member
I think that the difference lays in the form of Nitrogen that they use...
If is Urea is gona be slow releasing...otherwise no.
Like MendoGrowMore is totally soluble but if you go to the hardware store you may find that the urea coated ones are common and not fully soluble cause they are meant to be spreand on the soil surface (for lawns or orchards) instead of mixed with water for fertirrigation...


Yara for ex. has two different granulated products one soluble and another slow releasing....
Never tried any of em....but i guess thats important to keep in mind.
:joint:

You're correct. Not all nitrogen is equal, this one I'm using will make my plants skinner and taller, I don't remmeber the names of the nitrogen, it's written on the package it ain't the best for weed but it will do the job as I'm already into flowering. I just ran out of terra canna flores and I need to use something else as I have no way to get any rn
 

Los_Serpent

New member
1. This has way too much nitrogen, not enough phosphorus compared to potassium. If you're using solid and liquid nutrients it is best/essential to stick to nutrients and media meant for cannabis.

2. I am becoming a fan of complete fertilizers. So:

a) Use a supersoil

You can mix your own, as long as it has

N - blood meal, alfalfa meal/pellets
P - rock phosphate, bonemeal
K - vinasse, wood ash
Ca - magnesium lime, rock phosphate, bonemeal
Mg - epsom salt, maerl magnesium lime
Si - silica clay like Mineral Magic, Jersey Green Sand, etc.
S - epsom salt
Trace elements: lava meal, basalt meal, seaweed

Or you can buy ready made supersoil mixes. Or buy a heavily ferilized soil.

b) Make your own liquid nutrients

The best is to ferment cannabis parts - leaves, flowers - in sugar and water, with no air. Think of it as kombucha without the SCOBY.

Just use the leaves or flowers, reed sugar (any raw sugar because it has more nutrients) and cool water. The microbes on the plant are all you need for fermentation and what you're looking for because they're likely to be friendly to weed.

This is really effective, has everything cannabis needs in a liquid form, and has sugars in it which the microbes will used to further break down the nutrients in the supersoil.

You will need to use different parts of the plant for it's various stages - leaves from seedling through veg, flowers through flowering. Those can be cannabis flowers, hemp flowers, I'm using the flowering parts of stinging nettles right now.

Mega Crop is 9 7 17 and is meant for all the way to from veg to flower

Sure its not 15 9 15,but I'm. Using pk booster along with this so it shouldn't be an issue
 

Creeperpark

Well-known member
Mentor
Veteran
Too much nitrogen for flowers

Too much nitrogen for flowers

Nitrate nitrogen will release negatively charged anions and raise the pH in the root zone. However, ammonium nitrate, ammonium sulfate, or sulfur-coated urea will drop the pH and make the soil acidic. Look on the package and see what kind of nitrogen it has inside.

I would use caution putting any time-release fertilizer on any plant in concentrated liquid form. It may knock the hell out of your pH! You would probably get a much better effect using the fertilizer as the manufacturer recommends, only maybe using less.
 

Los_Serpent

New member
Nitrate nitrogen will release negatively charged anions and raise the pH in the root zone. However, ammonium nitrate, ammonium sulfate, or sulfur-coated urea will drop the pH and make the soil acidic. Look on the package and see what kind of nitrogen it has inside.

I would use caution putting any time-release fertilizer on any plant in concentrated liquid form. It may knock the hell out of your pH! You would probably get a much better effect using the fertilizer as the manufacturer recommends, only maybe using less.
9% ammonium 3% nitrate

But if this has too. Much nitrogen, doesn't mega Crop too? Sure its 15 vs 9,but i add a pk booster, so it should be pretty similar.

What the manufacturer recommends is a ripoff just like all weed fetilizer (exepct mega Crop, not in stock tho)
 

Grapefruitroop

Active member
9% ammonium 3% nitrate

But if this has too. Much nitrogen, doesn't mega Crop too? Sure its 15 vs 9,but i add a pk booster, so it should be pretty similar.
Well.....you are touching now a delicate argument lol......
Some peeps claims its too much some other says its just perfect as it is....
in any case it seems easy to adjust to your needs

I use megacrop, really happy with it, but i was one of those who thinks it may be too much N for middle end flowering...So after week 3 i was used to switch to Maxibloom...
Now im kind of rethinkin it cause i was always in need of calmag because of my demandin enviroment (LED +co2) so after week 3 im alternating maxibloom 7gxGal with Megacrop 6gx gal+2gxgal epsom salts....and everytime i feed megacrop the plants are very perky and vigorous much more than after Maxibloom....
Next run ill try megacrop till the end prolly boostin a little the P....
I would say that it could def be too much N if the strain is sensitive and you are under HIDs ina vented room...but ...again....its my opinion.


ah....found this link on the different form of N....
https://greenhouse.cornell.edu/crops/factsheets/nitrogen_form.pdf
 

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