Need Help: Understanding ppm and EC

jhartley295 said:

Does this mean my water in is basically 1.0 EC and runoff EC is up to 4.0? (2000÷500)

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Yes.

The 2000ppm runoff would concern me in my environment, especially at that stage of growth. This stuff may depend on the soil you use, the nutrients. But, for me, during late veg I have 900-1200 ppm runoff. After transition, my ppms become volatile. They rise quickly. I found that, if they reach 2400-2500ppm, that's where lockout occurs. I dialed in my feeding strength (and runoff volume) such that they stay around 1600-1800. I become concerned if they go higher. 2000ppm would cause me to feed less, more volume. 2200ppm would cause me to feed half-strength an 100% runoff. (In this range the runoff ppms are very twitchy. They climb fast. It may be due to the soil acidifying from the salt build-up, making the nutrients less available, causing more to remain in the soil. It spirals out of the control quickly at 1800 and above.).

This may depend on the soil and nutrients a grower uses. For me, the above is how it works. I would keep an eye on your runoff ppms. If you start seeing stress, deficiency, I'd pin it on salt buildup. (But, your runoff ph doesn't suggest a problem is brewing. My soil ph tracks the runoff ppms. It goes lower as the ppms go higher. I don't test runoff ph because it seemed ambiguous, depending on how long the water remained in the soil, how concentrated or dilute that amount was. There is a precise way to do it called the NCSU Pour-through extraction method. But, I was always too lazy to do that. Others use a slurry method. I ended up using a relatively expensive soil ph probe. That's what I used to see the soil's pH track the runoff ppms. At 2000ppm the, the soil would be around 5.0. That's not as bad as it sounds because the ph rises as the soil dries.).

Thanks, az2000. That is valuable info. right there!

"After transition, my ppms become volatile. They rise quickly. I found that, if they reach 2400-2500ppm, that's where lockout occurs."

That describes my closet grow problems to a tee. It started shortly after pre-flower. (in my case, high N, possible Ca excess from hard water + nutes, causing an Fe deficiency.)

The spot-on PH runoff is what was confusing me, in my shed grow. not matching the high ppm runoff levels.

What is also confusing, is the soil feed schedules from nutrient mgfr's...at this stage in week 5, they say 2100 ppm feed level. In my closet grow, I'm fighting N excess due to high ppm well water and what might be iron lockout.(from too much calcium?) I was feeding at less than 1/2 strength to boot.

But hot soil when transplanting and hard water must be the culprit.

I got some really great feedback on that thread (including yours!), now it's locked?

I can't thank everyone there now...so THANKS ALL! New RO system arrives today! Now I'll have to really pay attention and get the nutes right starting with clean water. So, I'll follow the advice in the other thread: 1/2 well water/ half RO, build nutes slowly after one or two waterings first, since the soil should have some nutes left after flushing twice pot size. And let the girls tell me what they want from now on!

Whoever said an old dog can't learn new tricks just missed it a bit...It just takes a lot longer to sink in these days WITH some generous. knowledgeable people sharing their valuable experience. :p

There is no point in testing soil runoff. That is more geared for soil-less non amended mediums and even then it's not really a good tool to use if you are a newer grower unless you really understand feeding cycles and the medium you are using. That won't give you an accurate reading on anything and basically is giving you a false sense of whats going on.

I'm figuring that out by feeding a 1/2 gal pot with 6.5ph/780ppm/71°F nute solution.

50% run off @ 2400ppm. Diluted runoff with distilled to make another liter @ ~1200ppm in/out 2480ppm. Useless as you know what on a you know what!

Ph out both times 6.2. I guess that and ppm input is what is important with soil? Now I'm out of distilled water and can't lower input ppm but I've got way more plants than I have lights and space for , so I'm experimenting on them.

This particular Gold Leaf fem has been in Happy Frog 1/2 gal pot for 6 weeks. I would think the nutes would be gone, especially after flusing, and runoff ppm would match input solution?

Obviously, I don't understand soil medium or feed cycles or nutes or...

My last grow (first attempt) 2 yrs ago I harvested 15oz from 3 autos using home-mixed soil and hard well water. Figures...trying to get more technical made it a lot more confusing and fussy.