EC question

[gangadoctor]

hi guys, first post but been lurking around for over a year;

i'm growing in a 9 pot alien dwc system with a header pot (brain with float valve) and a 100 litre back up res using dutch pro nutes. grow room equipment consists of x2 675w gavitas and x2 600w budmaster led's on light movers, split aircon inverter unit, co2, air scrubber, dehumidifier and humidifier and water cooler in my closed grow space. only my 3rd grow (1st one in dwc).

here's my issue...

my water temp is 18c, ph is a constant 5.8 and ec is 1.1. plants are in 2nd week of flower. my last water change was 14 days ago and none of these readings have changed in the last 14 days. the water level in the 100 litre res has depleted by about 75 litres (which was ph'd to 5.8 - no nutes) over the week and the dehumidifier is doing its' job.

i can't understand why the ec level isn't changing. i haven't added any new nutes for 14 days. the plants look very healthy and vibrant and i'm not sure what to do or where i'm going wrong - i mean do i just leave everytinh alone till the next water change. having said that - everything is fine?

coffee

 

[go4snypr]

The only reason the ec would stay the same is if the plant is using the same ratio of water to nutes. In theory that is exactly what you want. I would be surprised if it stays that way for any length of time though.

 

[gangadoctor]

Fair enough but surely 14 days is long enough? Also, as the leaves evaporate water/nutes and new water/nutes are absorbed from the roots the ec would have declined by now. Bearing in mind about 75 litres of water has been used as top up from the res... Which is only oh balanced and no nutes?

 

[go4snypr]

The EC will only change if the nute to water ratio changes. if the plant is using an equal ratio of nutes to water, the ratio stays the same, so the EC stays the same. If you are topping up the res with ph adjusted water with no nutes and your EC is not changing, then I would suspect your meter is faulty.

 

[gangadoctor]

No the metre is fine. I'm using bluelab guardians and they're the dogs bollox. I've used both metres in the solution just to be double sure and I've also used a pen ec reader. All reading literally the same ec.

This is why I'm so mythed you see... I've on purpose left my nite mixture weak and the ec hasn't moved. My base ec is 0.7. I would have thought after 14 days and 75 litres of plain water added in the ec would have decreased.

As I've already mention the plants look great. Strong and bright green with no deficiencies or burns.

 

[go4snypr]

so if I have this correct you mixed up a solution to 1.1. Let the plants feed for 14 days and what was lefts was still at 1.1. You then added a bunch of water at 0.7 and the res is still 1.1??

 

[gangadoctor]

Yes I've mixed a solution to 1.1. Let the plants feed for 14 days and the ec is still 1.1. And the dwc system is linked to a 100 litre res via a float system which automatically drip feeds water into the plants as its depleted. To date 75 litres has been transferred only ph balanced

 

[gangadoctor]

Surely the ec has been diluted enough to show a lower reading?

 

[go4snypr]

I would think so.