Why is runoff EC spiking?

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phxazcraig

phxazcraig

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I've been watching my runoff EC all grow, and until flowering, it was always quite a bit lower than input.

Until I hit flowering. Why?

Now, despite adding longer watering times to get perhaps 40% runoff, my EC is 600 higher than input - hit 2000 for an input of 1450 last night.

I'm growing in coco/perlite, 5x daily watering. Plants just finished 4th week since 12/12 flip, and they generally look very healthy. When the EC started rising I noticed a small bit of tip burn.so I backed off on EC for a week, and the tip burn went almost all the way away, but not quite. That was an EC over 1200 or so. But after a bit of a drop EC still went up. When it hit 700 points higher than input I added more time to each watering, to get 40% (or more) runoff. EC dropped for a bit, but now is rising again. Last night I threw some RO water into the reservoir to dilute EC to 1200, and EC dropped 100 points today. This crop has done well on lower EC, so I think maybe I'll just keep it lower.

In the meantime, let's speculate, unless you know what's going on here.

I changed a couple of things when I flipped to flower. Around that time I started putting H2O2 into the reservoir. I also changed the nutrient ratio (per GH mid-level charts) and I started using Floralicious and Liquid Koolbloom. The LED power has been OK or a bit high throughout. I kept PAR above 700 through final veg and am up to 1000 or more now, because of plants crowding the light.

I'm wondering why the EC keeps building in two ways:
1. Something in the nutes is not being absorbed and is building up. (I'm wondering about Floralicious). Also note flushing out much.
2. My plants are simply not eating the nutes like they were before they lost 6 hours of light.
3. Something in the pots other than my plants was eating (processing?) nutes and is not now - perhaps good microbes killed by the H2O2?

And - should I do some sort of flush, perhaps RO water with just cal/mag? Water with that continuously until EC comes down a bunch?
 
jguit

jguit

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Increase watering frequency? or maybe they're just light feeders.

Try resetting/flushing your media to 1 EC with just your base nutrients and run at 1 EC for a few days and see if it's any better. If that helps, then maybe add liquid koolbloom to the mix at 1/2 strength on top of your base feed.

are you giving them a watering when the lights are out?
 
Last edited:
jguit

jguit

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I though we were talking EC? I've seen some people give EC readings in microsiemens instead of the usual millisiemens.
 
Dirtbag

Dirtbag

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I though we were talking EC? I've seen some people give EC readings in microsiemens instead of the usual millisiemens.
Could be. I've seen all kinds of backward interpretation of numbers here so maybe I'm jaded lol.
If it's 1.4, I'd still say that's a bit high. In early flower you often get a runoff spike, it happens.
 
phxazcraig

phxazcraig

519
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Could be. I've seen all kinds of backward interpretation of numbers here so maybe I'm jaded lol.
If it's 1.4, I'd still say that's a bit high. In early flower you often get a runoff spike, it happens.
Based on my one grow so far, I'm associating flowering with an EC spike. As long as it goes down. I'm closely following a GH feed chart, except typically been diluting it by about 200 points on whatever scale I'm on. Which is either 1.4 or 1400 instead of rhe 1.6 or 1600 on the chart. Is it typical for it to drop back down?
 
phxazcraig

phxazcraig

519
93
Increase watering frequency? or maybe they're just light feeders.

Try resetting/flushing your media to 1 EC with just your base nutrients and run at 1 EC for a few days and see if it's any better. If that helps, then maybe add liquid koolbloom to the mix at 1/2 strength on top of your base feed.

are you giving them a watering when the lights are out?
Yes, there is a 2am feeding. Lights are on 10am to 10pm. Using schedule from cocoforcannabis. Plants look good.
20220317 213138
Here is a quick cell phone shot of a branch in the brightest area. Seems ok to me.
 
Dirtbag

Dirtbag

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Based on my one grow so far, I'm associating flowering with an EC spike. As long as it goes down. I'm closely following a GH feed chart, except typically been diluting it by about 200 points on whatever scale I'm on. Which is either 1.4 or 1400 instead of rhe 1.6 or 1600 on the chart. Is it typical for it to drop back down?
Yep absolutely, by week 4 or 5 it's starts slowing down, just keep up with either lower ec feeds or more runoff to keep the ppm in check and you'll be fine.
 
phxazcraig

phxazcraig

519
93
Yep absolutely, by week 4 or 5 it's starts slowing down, just keep up with either lower ec feeds or more runoff to keep the ppm in check and you'll be fine.
Flipped to 12/12 Feb 15, so just finished week 4. I've read a few times that Sour Diesel may take an extra three weeks (11 total) in flower. I'm treating that like an extended middle flower, per a GH chart.
 
E

Enzo

17
3
If you are getting an increase in your run off EC and you have 5x a day watering frequency I would recommend verifying your pots water content. Crop steering and water content are great topics to look into.
It sounds to me like your getting to large a dry-back during irrigation’s creating channels and increasing EC.

Some best irrigation strategies are to start with your deried EC and flush your root zone till EC in = EC out. This could also be considered “field capacity”. Meaning the maximum amount of solution your medium can hold. In coco filled 1 gal pot it’s like 54% before you start getting runoff. That’s a good start for within 2 hours of lights turning on.
From that point you want to manage your dry backs between irrigation events. Let’s call “field capacity” 100%. If your plant uses 20% of that water in the pot in 1 hour you would call that a 20% dry back. If you have a 20% dry back, because there is less water in your medium your EC increases. It may only be by .1 or less but it does increase as EC is a measure of total dissolved solids within the water content.

OK so now we know how the EC goes up. So let’s talk about the irrigation strategy. If after that hour you were at the 20% dry back and you irrigate but don’t replenish the entire amount of the dry back (never reaching field capacity) your medium EC will be higher than the input EC. Maybe by a little or maybe a lot. It just depends on the amount of dry backs and how frequent the irrigation‘s and how long those irrigations are. If you’re never getting back to field capacity after the first irrigation then every irrigation there after your EC is technically just going up and up and up. Even if you get some run off at the end of that day let’s say unless you were completely flushing your medium to bring it back to the input EC value you would never get back to that value ultimately ending in a nutrient toxicity.

So with that being said let’s say after your first hour you dry back 20%, if you were to irrigate long enough to get to total field capacity (100%) with no run off or very little your EC for your medium should now be back to roughly your input EC. ( until this is dialed I recommend a tiny bit of runoff every irrigation). Dry back 20% and irrigate again getting some runoff. It doesn’t have to be a lot but it lets you know you’ve hit field capacity with getting some runoff.

This is called crop steering. By managing the dry back percentage, the frequency of irrigation and the length of those irrigation‘s one can manage a plants production focusing either on more vegetative or more flowering aspect of growth.

And just one other note technically a plant doesn’t require a dry back as is shown in the DWC or flood and drain style of growing. However in coco the dry backs can be extremely important in a plants initial root growth and exploration as well as the more aggressive vegetative and flowering phase. ✌️
 
phxazcraig

phxazcraig

519
93
If you are getting an increase in your run off EC and you have 5x a day watering frequency I would recommend verifying your pots water content. Crop steering and water content are great topics to look into.
It sounds to me like your getting to large a dry-back during irrigation’s creating channels and increasing EC.

Some best irrigation strategies are to start with your deried EC and flush your root zone till EC in = EC out. This could also be considered “field capacity”. Meaning the maximum amount of solution your medium can hold. In coco filled 1 gal pot it’s like 54% before you start getting runoff. That’s a good start for within 2 hours of lights turning on.
From that point you want to manage your dry backs between irrigation events. Let’s call “field capacity” 100%. If your plant uses 20% of that water in the pot in 1 hour you would call that a 20% dry back. If you have a 20% dry back, because there is less water in your medium your EC increases. It may only be by .1 or less but it does increase as EC is a measure of total dissolved solids within the water content.

OK so now we know how the EC goes up. So let’s talk about the irrigation strategy. If after that hour you were at the 20% dry back and you irrigate but don’t replenish the entire amount of the dry back (never reaching field capacity) your medium EC will be higher than the input EC. Maybe by a little or maybe a lot. It just depends on the amount of dry backs and how frequent the irrigation‘s and how long those irrigations are. If you’re never getting back to field capacity after the first irrigation then every irrigation there after your EC is technically just going up and up and up. Even if you get some run off at the end of that day let’s say unless you were completely flushing your medium to bring it back to the input EC value you would never get back to that value ultimately ending in a nutrient toxicity.

So with that being said let’s say after your first hour you dry back 20%, if you were to irrigate long enough to get to total field capacity (100%) with no run off or very little your EC for your medium should now be back to roughly your input EC. ( until this is dialed I recommend a tiny bit of runoff every irrigation). Dry back 20% and irrigate again getting some runoff. It doesn’t have to be a lot but it lets you know you’ve hit field capacity with getting some runoff.

This is called crop steering. By managing the dry back percentage, the frequency of irrigation and the length of those irrigation‘s one can manage a plants production focusing either on more vegetative or more flowering aspect of growth.

And just one other note technically a plant doesn’t require a dry back as is shown in the DWC or flood and drain style of growing. However in coco the dry backs can be extremely important in a plants initial root growth and exploration as well as the more aggressive vegetative and flowering phase. ✌️
My take out of this is that I should try rotating or moving my halo drippers so the input isn't always in the exact same spot.

Unfortunately, I don't think I have any way to measure dry back. Can't lift the pots to weigh them because of the net, mostly.

I've thought about the idea that I'm getting wet/dry channels in the coco - but... hmm. I do add Yucca powder as a wetting agent, and I've not noticed any dry areas on the surface. I'll fiddle with the halos a bit, and I think I'll send a few gallons through via hand watering to make sure things are completely wetted. This is one time I'm inclined to just empty the reservoir in one long watering, and then pour the runoff back into the reservoir, with a couple of gallons of RO water. (Gets old mixing nutes.)
 
phxazcraig

phxazcraig

519
93
I'm going to try to dissect this for better understanding.
If you are getting an increase in your run off EC and you have 5x a day watering frequency I would recommend verifying your pots water content. Crop steering and water content are great topics to look into.
It sounds to me like your getting to large a dry-back during irrigation’s creating channels and increasing EC.
OK.
Some best irrigation strategies are to start with your deried EC and flush your root zone till EC in = EC out. This could also be considered “field capacity”. Meaning the maximum amount of solution your medium can hold. In coco filled 1 gal pot it’s like 54% before you start getting runoff. That’s a good start for within 2 hours of lights turning on.
From that point you want to manage your dry backs between irrigation events. Let’s call “field capacity” 100%. If your plant uses 20% of that water in the pot in 1 hour you would call that a 20% dry back. If you have a 20% dry back, because there is less water in your medium your EC increases. It may only be by .1 or less but it does increase as EC is a measure of total dissolved solids within the water content.
Understood.
OK so now we know how the EC goes up. So let’s talk about the irrigation strategy. If after that hour you were at the 20% dry back and you irrigate but don’t replenish the entire amount of the dry back (never reaching field capacity) your medium EC will be higher than the input EC. Maybe by a little or maybe a lot. It just depends on the amount of dry backs and how frequent the irrigation‘s and how long those irrigations are. If you’re never getting back to field capacity after the first irrigation then every irrigation there after your EC is technically just going up and up and up. Even if you get some run off at the end of that day let’s say unless you were completely flushing your medium to bring it back to the input EC value you would never get back to that value ultimately ending in a nutrient toxicity.
But basically, you should have 100%/field capacity if you are getting runoff, correct?
So with that being said let’s say after your first hour you dry back 20%, if you were to irrigate long enough to get to total field capacity (100%) with no run off or very little your EC for your medium should now be back to roughly your input EC. ( until this is dialed I recommend a tiny bit of runoff every irrigation). Dry back 20% and irrigate again getting some runoff. It doesn’t have to be a lot but it lets you know you’ve hit field capacity with getting some runoff.
I'm pretty sure I'm over 30% runoff on most feedings. The first one in the morning is a little short of that because the only feeding between 8:30 and 10am is at 2am. Otherwise there is a watering at 10am, then every 3.5 hours after that until lights out. (I actually start the first watering 5 minutes after the lights come on).

I get runoff from every watering event, and this goes back to week 1.
This is called crop steering. By managing the dry back percentage, the frequency of irrigation and the length of those irrigation‘s one can manage a plants production focusing either on more vegetative or more flowering aspect of growth.
That's what I'm attempting, I think.
And just one other note technically a plant doesn’t require a dry back as is shown in the DWC or flood and drain style of growing. However in coco the dry backs can be extremely important in a plants initial root growth and exploration as well as the more aggressive vegetative and flowering phase. ✌️
I guess one variable I haven't really measured is how much water is used between feedings, runoff+evap+plant use. I don't really know how wet/dry the coco is. I've just assumed it was wet throughout. My feedings are 35 seconds, by the way. I say about a gallon per feeding/split over 4 plants. Somewhere around 5+ gallons a day going in, and about 4 gallons a day in runoff. It's a lot.
 
E

Enzo

17
3
Day 8 of flower currently getting dripped on 4 times a day with zero runoff, getting roughly a 15-17% dry back before every irrigation. Temp 82 humidity 68% input EC 2.8 media EC is currently 2.9.
E13F2564 E795 49CD A93F 8677BF1181AD

As far as the halo drippers I have never used them. But coco has excellent wicking capabilities. Which I love because when I drip on it I drip slowly for long periods of time giving the coco ample time to wick. When the rate of drip is increased the weight of the solution pushes runoff out before saturating the media completely.

you are correct that runoff = 100% field capacity as long as the dripping was slow enough to fully saturate the media. Remember too fast a drip just pushes out runoff before it can wick completely.

And remember the larger the dry back the higher the ec will go, which means the longer the next irrigation must be to bring the ec levels back to the input ec. The shorter the dry back the smaller the EC will climb and the shorter the irrigation shot will need to be. Short dry backs with short irrigations require smaller shot sizes more frequently. The more feedings the more oxygen is brought into the medium via capillary action. So technically a plant getting 20 x 5 second shots will get more oxygen then a plant getting 5 shots 20 seconds long.
 
jguit

jguit

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Great information @Enzo! Thank you for sharing. I'm going to do a little bit of experimentation on my next coco run and try to do a generative/reproductive steering attempt with coco. More frequent shots in veg and more dry back flower. I haven't seen much info about steering in coco. Thanks again.

The only time i saw a big EC runoff spike was in the beginning of flower as @Dirtbag mentioned. Once I got up to around 10 fertigations per day, my runoff EC is only a few points higher than input with no visible problems with my plants.

That said, my shots happen fairl quick, 250ml per plant in 1 gallon pots in 10 seconds and havent noticed any major salt buildup, at least nothing i'm overly concerned about. Runoff is never more than .4 EC more than the input. When you say drip slower for better wicking, how long are we talking about per fertigation event?

Thanks again!
 
jguit

jguit

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906
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But basically, you should have 100%/field capacity if you are getting runoff, correct?
I think the takeaway is that if you are feeding too fast, even though you're getting runoff it may cause channeling in the coco by not letting it fully saturate causing an EC spike.

I think in my case, even though my shots only take about 10 seconds, my frequent feeding schedule (x10 a day) somewhat mitigates the buildup. I'm going to do some experimenting on my next run with slower fertigation events.
 
Peat_Phreak

Peat_Phreak

206
63
When runoff is higher than your feeding EC, it means your plant is not eating all the nutes you are providing so it builds up. Remedy is to flush with pH water until EC is around 800ppm. Then feed at a lower ppm than you were before.
 
phxazcraig

phxazcraig

519
93
This morning runoff went down to 1700, but I had dropped the input to 1200. I have a bit of opportunity here to do some experimentation.

First - channeling of runoff - indeed for 30 seconds the halo drippers don't drip, they have a pretty fast little stream there. I have two options here to mitigate that.
-I have a ball valve on the input side that sits in front of the plants. It's wide open, but I could dial in a restriction to slow the stream down, then double the watering time to make up for it. Problem here is the inability to get any measurements of the water coming in. I cannot take the halos out of the put because the base of the plants is much bigger than the gap in the halo. I'll have to cut down the plants to get those halos off. However, I could pull the hose coming out of that ball valve, measure the unrestricted flow, the dial in a restriction that cuts the input in half, and start over figuring how long the watering cycle should last.

Second - dissipate the water under the halos more effectively. The halos consist of a plastic ring with more than two dozen tiny little holes in the bottom. They tend to spead the water pretty well as-is, but perhaps I should try to put something between the halos and the coco to diffuse the water more evenly. I'm thinking some sort of fibrous mat here, but haven't come up with an idea for the right material. Possibly I could simply cut up an old towel to the shape of the pot and lay it on top of the coco, under the halo. I really like this idea as it sounds like it would perfectly distribute water in the pots, but ... expect the unexpected. Wondering if anyone else tried something like this?

Third - I could most easily double the amount of feedings per day and reduce the watering time per runoff amount. My timer can be programmed up to 20 on/off events. But I lack a schedule for watering more than 5x daily.

Fourth - I could do some sort of flush, one time, by hand or by dumping the whole reservoir. I'm inclined to try this via hand-watering, and I have a flush product called FloraKleen I've never tried.
 

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