yello
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Fertilizer (NPK) - I don't get it.

I am new to hydroponics and I am still deep in the learning phase, but when it comes to fertilizer in the not learning phase.

I wanted to mix my own fertilizer as I found some hints what to mix in a book. In the book there is an example:

Code: Select all

Hydroponic nutrient recipes

To make 1.00 gallon(s) of FLOWERING NUTRIENT 5.5 - 7.97 - 18.4

Use 
4.10 grams of Calcium NitrateCa(NO3)2
2.80 grams of Potassium Nitrate KNO3
0.46 grams of Potassium Sulfate K2SO4
1.39 grams of Monopotassium Phosphate KH2PO4
2.40 grams of Magnesium Sulfate MgSO4 * 7H2O
0.40 grams of 7% Fe Chelated Trace Elements See Trace Box
So far it's clear. Then I downloaded the spreadsheet "saltmix3". When I type in the numbers there I get NPK of 264-82-424 based on those gram and 1 gallon. (I ignored the 0.4g Fe)

Can somebody explain that roughly? Or give a link (that is suitable for dummies)?
Attachments
saltmix3 XLS
saltmix3 XLS

evtubbergh
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You should probably link to the original spreadsheet so anyone willing to really look can see the calculations behind it.

In short though; that does not seem to be a ratio but the amount of each element or compound in parts per million, which is much lower than solid fertiliser. This is for a reason though, because if you're doing this hydroponics you need very low concentrations or you will burn your plants. In soil the concentrations are higher and they release slower as they dissolve.

Actually it is still a ratio just not like you're used to seeing as percentages :)

evtubbergh
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So just for fun to convert it to what you would see on a bag of solid fertiliser:

264 N 82 P 424 K (ppm)

0.0264-0.0082-0.0424 (%)

But I may be wrong and those values are for elemental K and P. The values on the bags are actually for the compounds (P2O5 and K2O), which mean there is actually less of each element along with other oxygen. (N is always the same because it is stable as just N)

yello
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I guess I confuse NPK and PPM. I need to do my homework :-)

valley
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NPK- nitrogen, Phosphorous, potassium, - PPM parts per million

Richard

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feldon30
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yello wrote:I guess I confuse NPK and PPM. I need to do my homework :-)
N – nitrogen: promotes the growth of leaves and vegetation
P – phosphorus: promotes root and shoot growth
K – potassium: flowering, fruiting and general hardiness

If a bag of fertilizer has an NPK rating of 6-12-9, then it has 6% Nitrogen, 12% Phosphorous, and 9% Potassium. If you think about those descriptions above, you can see why tomatoes and peppers do better with a low N, medium P, and high K. You want lots of flowers and fruit, not a large bushy green plant with hardly any fruit!

PPM - Parts Per Million as indicated above.

evtubbergh
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To be clear; 1 ppm is 1 millionth of the total. Like % is 1 hundredth.



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