Jacks 321 & PK booster

Apologies if this has been asked, I didn’t find it searching.

I bought a PK booster to add during flowering. However, I am unsure when to add it. I add Cal/Mag & silica before jacks but I just want to be sure. Thanks in advance!!!

Depends on pk booster, what else is in it, and what you expect it to do. Following the traditional 321 recipe the final npk ratio is about 3-1-4 with just the base nutrients. Most that mess with this kind of stuff try to level out p and k through transition and change final npk ratio to something more like 1-1-2.

I don’t really know that either is best you’ll do. But easiest way to fall in line with that change is to use mkp.

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It’s called Sonic Bloom and it’s 0-51-34

Sounds like MKP generally.

Most do this:
Booster mix (grams per gallon)
Jacks Part A/ Cal nitrate (Part B) / Epsom salts / MKP
2/ 2.7/ 2/ 1.2

I would only do that for about 2 weeks when I did this mix. Too long and there’s an N overload from the heightened Part B.


Thank you so much!!!

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This is a comparison of several nutrient mixes to Jack’s traditional 321 mix and MKP mix

The standard MKP I used was 2 / 2/ 2 / 1.2MKP as shown in the table. And as @dbrn32 pointed out the basic NPK ratio is roughly1-1-2. Where the Hydro mix is roughly 3-1-4


I did this the last two grows: right at the flip for three weeks.

You don’t need cal mag if using Jack’s FYI.


I probably confirmed the amounts with you before I used it. On this grow I am giving Jack’s 10-30-20 blossom booster another try. Running it for 2 weeks (rather than only 1 per Jack’s feed schedule). Returning to TAP until I use Jack’s 7-15-30 Finish for the last week or two.


My little bag of MKP is 0-52-34. Basically the same thing. I used the ratio @Graysin posted first three weeks of flower last grow and had good results. Next grow I’m gonna use it for two weeks then switch to normal Jack’s recipe with big bud powder for weeks 2-5.

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