Relationship between PPM in and PPM out

troutfarm said:

Hi everyone, I'm just finishing out my second grow in a long time and have one plant remaining, a small Amnesia Haze that I experimented with starting 12/12 from seed (I had extra room for a small plant in my room that just switched 12/12 for three larger plants).

This is my first grow using a ppm meter and I only started using half way through. My question is this, as the title states, what's the relationship between ppm in and out?

This AH is in a one gallon fabric pot with FFOF, perlite, and clay balls. It gets watered roughly every 3 days. 6 days ago I watered it with 10ml per gallon of my grow nutes which gave a ppm in of 940. The ppm out was 1500. (ph in and out was 6.4 for this feeding). The previous ppm out, 3 days earlier was 1170 for a net reduction of 610 ppm.

Three days later I watered with rested water only, which is 200 ppm in, and the ppm out was 1150, for a net reduction of 550. (ph 6.4 in and 6.5 out). I'm about to water tonight...

My question is this, given that I'm about 3 weeks from harvest and want max 1600ish ppm?? for mature flower, what should I mix my ppm nutes at today? Each feeding seems to "eat" 550ish ppm, so do I mix to 1000 ppm in so after the plant uses roughly 550, I'm left with 1600 out? Does this math even make sense?

And when the charts say a mature flower ppm range to target is 1100 - 1600 ppm, does that mean to hit that target for your mixed feeding going in? Or out?

I hope this post isn't too confusing... but I'm confused a bit.

View attachment 4130176 View attachment 4130179

Click to expand...

booms111 said:

So when you fed 900ppm and the out ppm was 1500ppm that showed a build up of unused salt build up. Next time if you want to follow ppm start right away with just the FFOF ppm until it's below 900ppm then start feeding around 500ppm. Keep a record of in and out and you will see a pattern if feeding right ppm levels. Try to keep your in ppm close to your out ppm #'s by a few hundred up or down, closer the better. I'd recommend not feeding so high next time also, try keeping your ppm feedings around 800ppm max and keep runoff ppm below 1000ppm. I like to give just plain water last 2 weeks, which should get you down to 500ppm or lower by harvest.

Click to expand...

troutfarm said:

Awesome booms111, this is exactly the info I was looking for! And makes great sense. I'm looking forward to starting my next grow and keeping track of ph and ppm data correctly from the start. Great info... thanks!!

Click to expand...

Kingrow1 said:

I think your hearing what you want to hear and missing how soil is run. I also believe ffof and such are quite organic and not much like your soiless peat so even less chance of using runoff data in any meaningfull way.

Its totally all down to you but most have said that soil isnt hydro and runoff is not anything to go off.

Click to expand...