HYDRO Nitrogen Phosphorus Potassium (NPK) ratio's - What ratio's work best for cannabis?

[FlyingDutchPaddy]

Hi fellow hydro (and soil/coco) growers,

TL;DR: What ratio of NPK do you feed your plants? How did you measure it?

Been doing some reading and research into NPK ratio's for growing cannabis, and have only found varying guidelines for the stages of seeling/vegetative growth/bloom periods.

On https://www.growweedeasy.com/best-hy...ients-cannabis , there is a general recommendation:

Optimal Hydroponic Cannabis N-P-K Nutrient Ratios
Life Stage	N	P	K
Vegetative/Grow	High	Medium to High	High
Flowering/Bloom	Low	High	High

Nitrogen (N) behaves as is, NPK of 5-0-1 (Flora micro) will give 5 N.
Phosphorus (P) and Potassium(K) are different.

Nutrients will show on the label - Available (P2O5) for the amount of phosphorus and (K2O) for potassium.

From: https://www.maximumyield.com/what-s-n-p-k-anyway/2/1220
"The problem is that the N-P-K labeling for the product does not show the actual concentration of these elements themselves (P or K only), but instead gives credit to the attached oxygen molecules.
For reference, the elemental concentration of phosphorus is 43.6% of what’s labeled and potassium is 83%."


Typically,

NPK Ratio	N	P	K
Micro	5	0	1
Gro	3	1	6
Bloom	0	5	4

For equal amounts of micro, gro and bloom (1.25ml) would result in a NPK ratio of:
N P K

2.7

2.0

3.7

If I take into account the elemental concentrations of NPK that are really there, it looks like this:
N P K

2.7

0.9

3.0

My question to you growers is:
- what ratio of NPK do you feed your plants?
- How did you get to that ratio?
- what amounts of NPK do your nutrients have on the bottles?


You can use the attached NPK calculator spreadsheet. NPK calculator - Copy.xlsx
Its based on Flora Micro/Gro/Bloom but you can modify for your nutrients.

[wheatgrass]

I just follow the instructions for Botanicare nutrients at half strength and it works great.
Unless you are trying to make your own batch.

[FlyingDutchPaddy]

NebulaHaze , SiriusFourside I hope you might be able to give some insight.

For context, the feed schedule I'm refering to is this one: https://www.growweedeasy.com/sites/g...t-schedule.pdf
It's for Recirculating Nutrient ScheduleGeneral Hydroponics Flora Series + CaliMagic.

The PDF above uses teaspoons as measurement, 1 tsp = 5ml.
A while back I made the chart below to help me with the amounts I need for my used water (showing a volume of 10 gallons as example).
Only recently I added the NPK ratio's to the right (those are not adjusted for actual P and K present)



When you adjust for P and K availability, 43.6% P and 83% K, the ratio's for P and K are lower.

See below when adjusting for the availability:



One would think, to increase the P and K ratio, you'd have to add more Bloom (0-5-4), but that changes the ratio's of N as well.
It becomes a balancing act to find a 'sweet spot' for NPK ratio based on the amounts of Micro/Gro/Bloom you add to the mix.

I suppose this goes for any nutrient mix you use from any nutrient company.

As such my question: what's the best ratio for N-P-K to grow the plants we do?

for seedling/vegetative growth/bloom periods.

Thanks for your insight!

[9fingerleafs]

i think you are overthinking it, the exact nutrient requirements will change according to the water you use, your environment, the light source, the set up (hydro) or soil contents and most importantly the strain. those numbers are just a guideline to know where to start and with some practice youll realize as long as you are providing enough without being too much the plants will do fine. you may try different nutrients and some will work better than others for you, this doesnt mean theyre the best, thay just work for you. i use botanicare too, its only a two part (grow & bloom) grow has lots of nitrogen and bloom has lots of PK

[kingfish]

k i s s ….

[FlyingDutchPaddy]

i'll adapt that to KISI - Keep It Simple Informed

after doing more research on NPK ratio's for general plant growing, I learned a couple of things regarding what each element does for the plant and how to create an optimal growing environment.
(I've seen this here on GWE as well,) there are two styles of growing in hydroponics - sterile root zone and the use of beneficial microbes in the root zone.

sterile is simple; no microbiology of any kind, use of hydrogenperoxide (or alternative) to kill all forms of life in the root zone.
using microbes and beneficial additives is the complete opposite - use what nature already has come up with to further increase plant growth.

beneficial bacteria - primarily to fight off and keep nasty bacteria in check (sensizym, hydroguard, ... )
beneficial fungi - root mass expansion, fungi aid in uptake of mineral ions (voodoo juice, Great White Powder, ... )
beneficial other element - Silicon - helps strengthen the plant, increased resistence (vitalink Si Max, Rhino Skin, ... )
naturally occuring chelators - organic molecules also found in soil that keep hold of the trace elements a plant needs during its life, like Fe (humic/fulvic acids, vitalink fulvic, ... )
amino acids, enzymes - promote cell devision, increased nutrient uptake, nature's catalyst for plant cellular chemical activity (b-vitamins, plagron green sensation, GO seaweed, ... )

the takeaway: using microbes and natural additives allow for increased nutrient availability, better nutrient uptake and healthier plants than would occur under sterile conditions.

other points:
- NPK labels usually show the % of the mineral of P and K.
for the P value of 5, the mineral P2O5 is shown at 5%.
the acutal element value of P is 44% of that P2O5, so P is closer to 2.2 rather than 5.
for K being 6, the mineral K2O is labled at 6%.
actual K is 83% of K2O, so 6 is actually close to 5.
- CalMag can have extra N in it, this will affect the NPK ratio of the nutrients.
- pH down (phosphoric acid) will add extra P.
- pH up (potassium hydroxide) will add extra K

Using 5 parts fulvic acid to 2 parts kelp/seaweed works 50% better in combination than either alone.
germinating seeds in water with fulvic acid & seaweed will improve germination rates.
consider a starter nutrient mix with slightly higher P in the beginning for increased energy,
when transitioning to flower, add a little more P for increased energy.
in veg stage, suggestion is that N to K ratio is 1:1.5
in bloom, suggestion is N to K ratio is 1:2.

Going to do my 3rd grow using all the above.

I've made my own feed schedule to start with as a guideline (and template for others) using the microbes & beneficials.
I can adjust for water quantity used, intended nutrient strength.
Tweak NPK ratio to account for NPK influencing additives (CalMag)

Feedback welcome!

Attached is the spreadsheet you can use as a reference, adapt to your own grow, modify as you wish. FDP Custom Hydro feed chart with NPK ratios - Copy.xlsx

And a screenshot example for 37.85L / 10Gal water


Knowledge sources:

https://medteknutrients.com.au/hydroponic-nutrient-science/

https://www.youtube.com/channel/UCmCRcRcueFHojHQ_U9Ud2mw/videos

https://www.maximumyield.com/contributors/harley-smith