Nutrient/EC RO

My source water comes from an RO machine which ouputs the water at ~0ppm then raises it back up to 35-50 ppm with CalMag. Confirmed by my EC meter, my water is regularly pumped out at 38ppm.

my EC meter has a resolution of 1uS/cm, and also reads ppm

As my environment is perfectly controlled and optimal - and after stumbling upon Ganja's post with recommended EC doses, i've decided to follow it to a T in an effort to perfect nutrition

I BELIEVE that the measurements Ganja quoted were in increments of mS/cm - under this assumption my EC meter should be reading 1400uS/cm to equal Ganja's stated "1.4 EC"

tell me if im wrong.

alright so here's the issue now that the facts are out of the way;

i've got a beautiful bush about 1.5 months old, she's in fox farms soil and it has been hot - runoff reading from my EC shows about 1700 uS/cm.

and indeed i've seen small signs of over-fertilization up until about a week or two ago, and i've not added anything to my water short of the already added cal/mag in an effort to avoid further burn.

for the first time i'm sitting down here to measure out some nutes and and water her with a self-proposed 1500uS/cm reading at a pH of 6.3. (i should add, the strain is 90%Afgan)

Im using bio-bizz biogrow and I'm sitting here adding ml's worth of nut to my 9 liters of water from the RO and i just now REACHED the manufacturers suggested dosage - I'm still nowhere NEAR 1500uS/cm, it's more like 700 if im lucky.

what am i doing wrong, where am i mucking up the science or misunderstanding something? it just doesn't make since that i would need to add 2ml per liter of biogrow to my water in order to meet an EC of 1.5. that's DOUBLE manu's suggestion for a fully mature plant


i guess the added question to all of this, is how do the EC meausrements you've given change in relationship to the "hotness" of your soil? do those EC readings assume nutrient neutral soil or maybe fox farms nutrient rich soil for example?

ive been working with biobizz for 6 years - im no newbie to their nutrition charts, and to be honest i wonder if you read my whole post based on some of your questions.

and let me be more clear, i am well aware of how these nutrients affect my plants. ive been using the same nutrient and soil for years - so i know generally what works for them already. the ONLY difference is the RO, and Use of an EC meter - and i know that from tap 2ml/liter will burn to shit a plant this age and size when its never been given supplemental nutrients before


on the other hand, you may possibly have a point in the fact that my RO water is sooo pure. the schedule for light mix rather than all mix might make sense but it doesn't change the fact that those numbers are in reference to what's already in your soil - not your water.

i think there are fewer people than we might imagine with the expertise to answer my question exactingly.

Ganja? help me out here. i guess the added question to all of this, is how do the EC meausrements you've given change in relationship to the "hotness" of your soil? do those EC readings assume nutrient neutral soil or maybe fox farms nutrient rich soil for example?

for everyone else's benefit here's the link to the EC listings:

Originally posted by Ganja EC (electrical conductivity) is the basic way of measuring the concentration of soluble nutrients in feed water. Absolutely pure water is not a particularly good conductor of electricity, and the more dissolved minerals contained in water, the better it conducts. Measurements like PPM, CF and TDS are based on the EC reading. EC is the measurement used for the plants that grow in the Museum. Seedlings should start out with very low EC – 1.2 - 1.4 Larger vegetating plants, rooted clones and mother plants can be given higher levels of feed – EC 1.4 -1.6In the first half of flowering, plants should start around EC 1.6 and be raised up to EC 1.7-1.8 by the middle of flowering. In the last weeks of flowering, Sativa hybrids will usually be fine with EC 1.8 -1.9;Indicas and Skunks can thrive with higher levels of nutrient – up to EC 2.0 - 2.2 (and generally need more nutrient in order to build their thicker buds).

well its one of two things - either i've finally figured out something important and itll take someone whos already figured it out to guide me through it

or i don't have a fucking clue what im talking about either

guess we'll see



and i have argumentative and aggressive tendencies, don't take it personally and just consider it an overflow of passion ;)

i've been thinking about going coco - at the moment i don't honestly remember my reservations regarding it but i seem to recall it had something to do with a tendency for nutrient lock out, salt build-up, possibly an issue with cal/mag? maybe pH instability? you tell me, what's the down shot of coco?

end of the day what I may very well do this next time is mix a neutral pH soil lacking nutrients but still a wetting agent with coco. maybe something like a 1:2 ratio favoring the soil. in this way I can retain the advantages of the soil while eliminating several of its disadvantages. the only thing i worry about is that I quite appreciate the simplicity of my watering with soil in large containers - its so nice to water so infrequently. it sounds like with coco i might want to set up some sort irrigation system for convenience sake. i'm one lazy son of a bitch

and regardless, none of this helps me at all, unless i can figure out how to measure my nutrients correctly. bottom line, my ec meter reads 231ppm, 470uS/cm (microsiemen/centimeter), or as i understand it 0.4 EC on ganja's scale. on this mix which is ~ 1ml/l bio grow/OR'd H20 and that just doesn't make any sense to me. i know my meter is calibrated on the simple fact that the ppm registers perfectly to what the OR documentation says the Cal/Mag ppm should be.   it's possible that with pure water i do have to add THAT much nutrient - but that just doesn't sound right to me for a veg'ing plant in soil.