Anyone growing in perlite? Results?

Porky101

Well-Known Member
N (NO3-) 115.853 5.3% +/- 0%
K 172.903 -1.2% +/- 0%
P 67.648 4.1% +/- 0%
Mg 50 0% +/- 0%
Ca 120.91 -3.3% +/- 0%
no your npk arent wrong, theyre what hydrobuddy says, your elemental real world P istill need conversion,, as K do too.
calc some common fertilizers and compare the ratio on the bag with what hydrobuddy state as ppm and fertilizer ratio, you will get the picture.
p insnt p2o5
and K isnt k2o


Ok I understand that.

What I am asking is, I always thought my formula, which has N (110) P (50) k(100) was an NPK ratio of 110-50-100. But now hydrobuddy tells me it is 1-1.04-1.14 NPK. SO what I am saying is, is my NPK wrong for Cannabis. I know cannabis like 3-1-2. I thought I had that by having 110-50-100. Are you telling me my ratio's are wrong?
 

cobshopgrow

Well-Known Member
no not saying theyre wrong, go after the real ppm.

Converting nutrient analysis to composition[edit]
The values in an NPK fertilizer label are related to the concentrations (by weight) of phosphorus and potassium elements as follows:

  • P
    2O
    5 consists of 56.4% elemental oxygen and 43.6% elemental phosphorus by weight. Therefore, the elemental phosphorus percentage of a fertilizer is 0.436 times its P value.
  • K
    2O consists of 17% oxygen and 83% elemental potassium by weight. Therefore, the elemental potassium percentage is 0.83 times the K value.
The N value in NPK labels represents actual percentage of nitrogen element by weight, so it does not need to be converted.

So, for example, an 18−51−20 fertilizer contains by weight
  • 18% elemental nitrogen,
  • 0.436 × 51 = 22% elemental phosphorus, and
  • 0.83 × 20 = 17% elemental potassium.

the 22 and 17 are your REAL ppm.
 

Porky101

Well-Known Member
no not saying theyre wrong, go after the real ppm.

Converting nutrient analysis to composition[edit]
The values in an NPK fertilizer label are related to the concentrations (by weight) of phosphorus and potassium elements as follows:

  • P
    2O
    5 consists of 56.4% elemental oxygen and 43.6% elemental phosphorus by weight. Therefore, the elemental phosphorus percentage of a fertilizer is 0.436 times its P value.
  • K
    2O consists of 17% oxygen and 83% elemental potassium by weight. Therefore, the elemental potassium percentage is 0.83 times the K value.
The N value in NPK labels represents actual percentage of nitrogen element by weight, so it does not need to be converted.

So, for example, an 18−51−20 fertilizer contains by weight
  • 18% elemental nitrogen,
  • 0.436 × 51 = 22% elemental phosphorus, and
  • 0.83 × 20 = 17% elemental potassium.


Ok but this is where I am confused.

I always believed you want an NPK ratio of 3-1-2. My PPMS reflect the 3-1-2.

Now I know you are saying that magnesium sulphate has S and MG. So with MKP you have the K and P component I understand this.

But it seems to me my NPK ratio is wrong now? My PPM ratio is alright.

I tried to input the Megacrop formulation in hydrobuddy but I dont get an NPK near what Mega crop are listing? I get an NPK of 1 - 0.28 - 1.74
 

cobshopgrow

Well-Known Member
btw. thats a problem.
most people refer to these ratios on the bag.
research papers maybe to elemental ppm.
nobody knows, be sure most people dont even know this and there is simply tons of confusion.
calculate fertilizer knowen to work in hydrodduy and go after the elemental ppm and their ratios, rest is just guesswork.
 

cobshopgrow

Well-Known Member
its all pretty confusing.
other countries other labeling.
whats on bag in the uk as ratios isnt the same as else where.

In the U.K., fertilizer labeling regulations allow for reporting the elemental mass fractions of phosphorus and potassium. The regulations stipulate that this should be done in parentheses after the standard N-P-K values, as in "15-30-15 (15-13-13)".[4]

convert your p and k from elemetal to p2o5 and k2o and the ratios it shows should fit.
hydrobbudy will show above fert prob like a 1.1x-1-1 or soemthing.
 

Porky101

Well-Known Member
My current formulation works out like this :

Veg :

N P205 k20 1-1.04-1.14
N P K 1-0.45-0.95 -----------------> This seems fine....
 

TintEastwood

Well-Known Member
Yep. It's confusing. Npk ratio vs Ppm in solution are not equal.

Assuming all US labeling...

Megacrop.
Bag label % 9-6-17 = Ratio 1.5-1-2.75

Jacks.
Bag label % 10-30-20 = 1-3-2 NPK ratio.

d0af1d8d7f8d67647dd691dc0117543e61097188.png

8fb7e7656055780f973980f20d5181fbdc4f35a3.png

Virtually same npk ratio 1-3-2 using other products.
Funky-Freebase.png

Capture+_2020-07-04-04-45-27.png
 
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cobshopgrow

Well-Known Member
yes, there is always a lot lost in translation for sure.
one can only really check the labeling and see if its P2O5 or P etc. and work with the real ppm after the eventually needed conversion.

european fertilizer state the Mg as MgO and Ca as CaO , USA gives elemental, Mg Ca,, to make the confusion even more complete.

as long you remeber P2O5 isnt P etc, youre fine.at least.
 

TintEastwood

Well-Known Member
So with that said....

I'm looking for NPK ratio recommendations for the different weeks of flower.

In the past I have not kept track of my ratios thru the grow.
 

cobshopgrow

Well-Known Member
if i would have some definitve ones...
would be mainly interessted in when mg is peaking and ca too.
i have this, but its general for all fruiting plants, not cannabis.
and i saw also different ones with different curves, so below could be simply not good for us, idk.

where the n goes down the fruiting starts, so basically our 12/12 switch.
fert.jpg
 

Porky101

Well-Known Member
if i would have some definitve ones...
would be mainly interessted in when mg is peaking and ca too.
i have this, but its general for all fruiting plants, not cannabis.
and i saw also different ones with different curves, so below could be simply not good for us, idk.

where the n goes down the fruiting starts, so basically our 12/12 switch.
View attachment 4614025
Nice chart.

Can you add the weeks in?

From my experience:

Week flower 1-3: Needs a ton of N CA MG.
Weeks 3-6 needs more P and K.
Weeks 6-8 needs mainly K.
 
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