EC readings when approaching harvest.

[2ShedsJackson]

I've been checking the EC readings of my feed water and then checking the run-off EC after letting it drain out for about 1 hour. I'm following the CocoforCanabis guide by which I mean keeping the run-off EC between 0 to +300 above the input feed EC. All's been well until this week when the run-off EC has gone crazy, over +1000 sometimes +1200!!
I'm wondering whether the plants reduce their nutes requirement when they're almost due for harvest or has something else gone wrong?

[Allotrope1000]

Hi, 2Sheds.
For my greenhouse grows (50/50 coco/perlite, 7 gal fabric pots, GH Trio + CaliMagic, 6.0 pH), I never checked my EC due to swings in the local public water supply. EC is high due to hardness.
Did you check the EC of your water source before mixing nutes? That could be a possible source of your high EC readings.

[2ShedsJackson]

Hi Allotrope1000,
I'm using rainwater, it stays almost constant at EC of ~140. I bought a 240ltr waterbutt specifically for this grow because the tap water is very hard and shifts about quite a bit.

I'm adding 1ml/ltr cal-mag which takes it up to EC 220, my 4-3-6 Grow juice will raise it up to 920 and the 2-7-4 Bloom and 0.1-0.1-0.1 Top Max will raise it to about 1000.

The last week I increased the Bloom & Top Max to Bio Bizz recommended which took it to about 1150. That's when the run-off EC started to go ape.

I've ditched the Grow nutes altogether today and just run with standard Cal-Mag, with Bloom & Top Max at half measures, EC in was 350, EC out was 1100. I'm gonna repeat later when it's wake up time ( they're on their 4hr break ). I'll report back with an update later.

I'm almost out of the Grow now but getting close to harvest so hoping they won't miss the nitrogen too much.

[Orggrwr]

Yes, it's normal for plants to reduce nutrient and water uptake the last couple of weeks. A sure sign you're getting close to harvest.

[2ShedsJackson]

Readings after 2nd watering = 2.0 ltrs in @ EC 300, 1.4 ltrs run-off @ EC 1050. Not much of a reduction. Plants look happy though.

[Bluey]

Reduce the EC as the plant begins to take up less water. I will reduce EC from about 1.6 to about 1.2 over those last couple of weeks....or there abouts.

I do not measure runoff pH or EC. Its too variable to make decisions on re your plants health