i would like to put a pepper seedling into a kratky setup, and i have some questions.
i'm inclined to use dyna-grow foliage-pro (9-3-6) because it is what i have.
the feeding guidelines on the label:
Maintenance: Mix ¼ – ½ tsp. per gallon of water with every watering.
Production: Mix 1 tsp. per gallon of water, once a week.
Monthly Feeding: Use 2 – 3 tsp. per gallon of water. Siphon Mixer: (1:15 ratio) Mix 2 – 4 fl. oz. per gallon of water for a concentrate feed solution.
Foliar Application: Mix ¼ – ½ tsp. per gallon of water and spray directly of leaves.
note that 1/4 tsp:gal is about 1:3000, and 1 tsp:gal is about 1:770
after searching, i've found suggestions for kratky all over the place basically from 1/4 tsp:gal to 1 tsp:gal.
i decided to mix up a test batch using 3/8 tsp:gal (1:2000). resisting the urge to use tap water, i actually used distilled water!
here are my measurements:
the last two entries are for this kratky experiment, but the others might somehow be helpful.
regarding the pH of the distilled water (5.6), i'm guessing there was some trace contamination. pH can swing easily with minimal solute in an unbuffered system.
so anyway, this test batch is pH 4.6 and EC 370 μS/cm. i have a feeling that i should increase the pH with NaOH to 5.5-6.5 (which will also increase EC), but then ultimately what EC should i shoot for considering i'm titrating an acidic nutrient?
i don't really understand the implications of EC beyond trying to use it to get some idea of nutrient concentration. i've read some posts with rhetoric about "don't use tap water as it will count towards your EC" as if to say that all contributors to conductance have an equally meaningful impact on plant health. i've probably misunderstood it? i don't get why we're looking at EC all the time instead of just relying on initial gravimetric and volumetric measurements (or better yet, testing for individual nutrients). what can EC tell you if you don't know what's contributing to it? is there some overall upper limit for EC where plants tend to get sick? if anyone can point me in the right direction, i'd appreciate it.
edit: if the suggested advice is to just give it 1/2 tsp:gal (using distilled water) or something like that and don't worry about it, i'd gladly take it
Edited by sinensis, 09 July 2018 - 07:39 PM.