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Old 06-25-2020, 10:48 PM #1
vcasqui
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Liquid fertilizer PPM doubts

Hello guys, I need your wisdom:

I readed ShroomDr's Nutrient Formula... a while ago. I liked the idea of mixing my fertilizers to give the right amount of nutrients to my plants, so I measured the weight of them and did the following calculations (I want to know the amount of nutes in 1ml/L):

Veg fertilizer (10-7-9): 1'2gr/ml -> ((1'2*1)/1000)*1000000 = 1200 ppm
N - 1200 * 0'1 = 120 ppm
P - 1200 * 0'07 * 0'436 = 36'6 ppm
K - 1200 * 0'09 * 0'83 = 89'6 ppm
Total = 246'2 ppm

CalMax (2-0-0)(3 Ca - 1 Mg) -> 1'1gr/ml -> 1100ppm
N - 1100 * 0'02 = 22 ppm
Ca - 1100 * 0'03 = 33 ppm
Mg - 1100 * 0'01 = 11 ppm
Total = 66 ppm

The thing is, when I measure the ppm with an EC meter, I get:

Veg fert: 1ml/L = ~0'3 EC (150 ppm)
CalMax: 1ml/L = ~0'35 EC (175 ppm)

I know that ShroomDr mentions in his thread that some products do not register EC, or they register too much EC in comparison with the actual "food for the plant" in them; but the readings I took are way too far off when compared to the calculations I did.

So my questions are: Are my calculations correctly done? Should I feed my plants following these calcs?

I usually trust maths above anything else, but I also don't want to kill my plants. If I want to achieve, say, 200ppm of Ca, then I should give them 6ml/L of CalMax (~2'1 EC), which looks crazy to me (and it's waaaay above of the 1'5ml/l recommended by Grotek).

So that's why I need your help. What should I do? I need you.

Thanks

Last edited by vcasqui; 06-26-2020 at 11:51 AM..
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Old 06-27-2020, 01:47 PM #2
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Originally Posted by vcasqui View Post
I know that ShroomDr mentions in his thread that some products do not register EC, or they register too much EC in comparison with the actual "food for the plant" in them;
I would take that as the final answer.
I was surprised on how high was gettin the ec after adding a humic acid product to up the ph....
no problems in the end.
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Old 06-28-2020, 08:05 PM #3
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Thanks man. I'll follow the calculations then.

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Old 06-30-2020, 03:57 AM #4
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Quote:
Originally Posted by vcasqui View Post
Hello guys, I need your wisdom:

I readed ShroomDr's Nutrient Formula... a while ago. I liked the idea of mixing my fertilizers to give the right amount of nutrients to my plants, so I measured the weight of them and did the following calculations (I want to know the amount of nutes in 1ml/L):

Veg fertilizer (10-7-9): 1'2gr/ml -> ((1'2*1)/1000)*1000000 = 1200 ppm
N - 1200 * 0'1 = 120 ppm
P - 1200 * 0'07 * 0'436 = 36'6 ppm
K - 1200 * 0'09 * 0'83 = 89'6 ppm
Total = 246'2 ppm

CalMax (2-0-0)(3 Ca - 1 Mg) -> 1'1gr/ml -> 1100ppm
N - 1100 * 0'02 = 22 ppm
Ca - 1100 * 0'03 = 33 ppm
Mg - 1100 * 0'01 = 11 ppm
Total = 66 ppm

The thing is, when I measure the ppm with an EC meter, I get:

Veg fert: 1ml/L = ~0'3 EC (150 ppm)
CalMax: 1ml/L = ~0'35 EC (175 ppm)

I know that ShroomDr mentions in his thread that some products do not register EC, or they register too much EC in comparison with the actual "food for the plant" in them; but the readings I took are way too far off when compared to the calculations I did.

So my questions are: Are my calculations correctly done? Should I feed my plants following these calcs?

I usually trust maths above anything else, but I also don't want to kill my plants. If I want to achieve, say, 200ppm of Ca, then I should give them 6ml/L of CalMax (~2'1 EC), which looks crazy to me (and it's waaaay above of the 1'5ml/l recommended by Grotek).

So that's why I need your help. What should I do? I need you.

Thanks
As long as your math is good you will be all set.

Remember you are measuring 100% of P205 with you Ec meter but your plant is only using 43.6% in P form but your EC meter will measure all of it. Same for K20.

Your EC meter is also picking up the dyes and preservatives in the nutrient solution as well.

Peace.
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Old 07-01-2020, 10:17 PM #5
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Yep, right now I'm feeding the plants based in the calcs I did. So far they seem to be ok, if not better than before (maybe it's too soon to tell, but they look happy). I'm being careful with the CalMax tho, since the base fertilizer already has some Ca and Mg in it, but I don't know how much exactly since the label doesn't specify it.

Right now I'm doing: 1ml/L veg + 1ml/L bloom + 0'5ml/L CalMax. This gives me:
N - 179
P - 78
K - 209
Ca - 17 (+ wathever the base fert has)
Mg - 6 (+ wathever the base fert has)

Which is pretty close to Ed Rosenthal's 200-70-200 for vegetative stage. The good thing is that it should be pretty easy to adjust if I feel like the plants need more/less of any nutrient.

I'm also trying to adjust the PH with wine vinegar to 6'7. But it's not as easy as it seems since it takes a while to stabilize, so I'm preparing my solution a day in advance and doing my best.
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