I run DWC and I use the 3 part gh nutrients. I usually just use a equal part of each but I've come to notice that it I add an equal amount of mml the ppm are equal. Just for example; say I add in 3 ml per gallon of grow and it equals 300 ppms. Then I add the same amount of ml of bloom but it'll only be 200 ml. My question is. Should I go by ppms or just milliliters?
Depends on whether you're trying to follow GH's schedule, or do your own thing. N, P and K (and other minerals) contribute PPM. Each of GH's bottles has different strengths of N, P and K. So, the amount you add of each gives you different NPK ratios. To get what GH believes to be the best NPK ratio, they tell you to use the MLs of each bottle.
GH's recommended schedule on the label produces this:
--------------- R A T I O S
-------------- N-P-K ---------- K-Mg-Ca ------- PPM
Seedlings -- 1.21-1.00-1.82 -- 5.48-1.00-2.67 --- 126
Mild veg --- 1.21-1.00-1.82 -- 5.48-1.00-2.67 --- 503
Aggr veg --- 2.07-1.00-2.98 -- 7.98-1.00-3.57 --- 970
Transition - 1.21-1.00-1.82 -- 5.48-1.00-2.67 --- 1005
Flower ----- 1.00-1.28-1.59 -- 4.00-1.00-2.12 --- 1040
That's full-strength. Normally growers cut it in half, so the total ppm in practice would be half of the above.
When I used GH Flora 3-part I used the
so-called "useless" schedule. It produces this:
--------------- R A T I O S
-------- N-P-K ----------- K-Mg-Ca -------- PPM
VEG
week-1 1.32-1.00-2.41 -- 6.76-1.00-2.15 --- 323
week-2 1.85-1.00-3.06 -- 8.08-1.00-2.82 --- 574
week-3 2.06-1.00-3.31 -- 8.54-1.00-3.07 --- 667 [continue as needed]
BLOOM
week-1 1.00-1.29-1.88 -- 4.54-1.00-1.77 --- 745
week-2 1.00-1.47-1.70 -- 3.75-1.00-1.90 --- 767
week-3 1.00-1.52-1.71 -- 3.65-1.00-1.88 --- 875
week-4 1.00-1.72-1.87 -- 3.53-1.00-1.66 --- 946
week-5 1.00-2.21-2.25 -- 3.33-1.00-1.31 --- 966 [cut in half if using bloom booster]
week-6 1.00-2.70-2.36 -- 2.91-1.00-1.23 --- 966
week-7 1.00-3.16-2.73 -- 2.88-1.00-1.05 --- 930
You can download
this spreadsheet to play with different different amounts of each bottle and see how the NPK and total PPM is affected.
