Trying to solve nutrient runoff issue before new Coco grow

[phxazcraig]

I documented my last grow in this forum in a thread titled 'Explosive Growth in Coco Coir'. Lots and lots of details of what happened in that grow.

It was successful - 28 ounces of Sour Diesel - but I fought nutrient issues all through flowering and never got a handle on it. Certainly I never understood the cause. So the purpose of this thread, hopefully not too long of one, is to figure out the probable cause(s) of the issue. Or maybe just the possible causes.

In a nutshell, the issue was that my runoff EC just get going up and up, even though I was watering crazy often - every 2 hours, with a gallon of runoff from each pot each time at peak. I would put in EC 1000, measure output getting up to 2000. This only happened in flower.

Before flowering, I built up EC in the nutrients per an average GH schedule. The EC of the output was always lower than the input. All that reversed in flowering - but why? I'm not the only one alarmed by high runoff EC. I can't figure out why it kept going up week after week. My ultimate solution was to drench the plants in RO water until the EC dropped to about the same as my input tank. But it then immediately started going up after that.

So - why?

 

[yobbocrack]

hey did the fan or new leaves have any burn during bloom.

 

[Zill]

Craig,

Perhaps you continued a feeding regime for a plant vigorously growing in a vegetative stage then it moved into flowering. Now that the plant is flowering, seeing its own mortality and slowing down the nutrient draw will be dramatically reduced.

Zill.

 

[daggarooker]

Did you experiment with lowering your ec? Maybe find a better equalibrium with the runoff?

 

[yobbocrack]

Now that the plant is flowering, seeing its own mortality and slowing down the nutrient draw will be dramatically reduced.

i thought nutrient uptake is more demanding during flower depending on the plant needs.

 

[CookiesLikeWhoa]

Outside of the rising EC, did you have issues with the plants that were related to over feeding?

 

[2Bad]

Try just watering every other feed instead of nutes everytime. I did that last grow seen great results.

 

[Zill]

Oh yes, it is very energy demanding. That's why if the plant is deficient in phosphorous the leaves appear purplish. Lacking phosphorus, the plants energy currency cycle (ATP/ADP cycle) cannot support photosynthates being elaborated into more complex carbon molecules, so the plant stores the carbon as purple pigments.

Back to the flowers, yes adequate phosphorous is critical but after flowers form and are set (or not with females) the gig is up. The plant begins to slowly senesce. You see it as the flowers deteriorate. So, at the point after the flowers are set nutrients play less and less role.

 

[Fromunda506]

Been growing in coco for years and worked through the same issue early on. Your plants were accumulating nutes from overfeeding. Once the salt builds up, it starts to lock out K and P. You can flush the EC down, but as soon as you feed it starts creeping back up. If it happens again, reduce your feed strength by 20% after you flush. Keep adjusting down until your feed and runoff are in the same neighborhood (ie, when she drinks, she is taking a proportionate amount of the dissolved nutes). I feed my coco girls 3-4 times a day in mid-flower. You are better with slightly less strong feeds more times per day if they look hungry. Coco is really easy to overfeed though. Buildup happens fast because of how frequently you feed. Important to get the feed regimen dialed or it can cause you all manner of headaches. Fortunately sounds like yours didn’t get too bad. Good on you. Cheers

 

[phxazcraig]

Let me try another shot at this, kinda hoping Aquaman will jump in at some point.

If you want to see what happened in my previous (and only) coco grow, look HERE: https://www.thcfarmer.com/threads/explosive-growth-in-coco-coir.136487/
I'm not going to rehash what happened in this thread when you can simply look in the old one. There are LOTS of pics and comments there. I'll say this, I got a nice crop from the last grow.

Now I'm trying to understand what happens to plants in flower, in coco, relating to salts build-up. I tried to follow both Aquaman and Cocoforcannabis recommendations for watering and feeding schedules, and that includes at least 20% runoff with each and every watering. My waterings were very frequent, up to 7x per day (every 2 hours, plus one at night) in full flower.

So again, here is the gist of it. Before flowering my plants sucked in all the nutes I gave them, and my output EC was typically 300 units smaller than input. After flower, that reversed, and the longer the plants flowered, the higher the runoff EC became even as I was reducing the overall amount of salts. At one point my input was 1000, but my outflow was 2000!

Here is the question: Why did the outflow EC continue to rise higher than the input even with 7x daily waterings with runoff amounts that were about equal to 80-90% of the input? It seems impossible that I could water at EC 1000 with lots of runoff, then repeat that 5 more times before the lights went out and at the end of that my runoff EC was higher than it started in the morning?

I'm not looking for a fix until I understand the cause.

Or - if I simply can't get a cause - then I'll try some fixes. I have an issue with the idea of feed-flush-feed-flush (which I think is a good idea to try) because I'm running a drain-to-waste feeding system with a 30 gallon bucket of nutrient solution. I'd almost have to engineer a second system running in parallel. And I don't think everyone else is having this issue, so I'm trying to understand what's going on.

 

[GrimReffer]

Let me try another shot at this, kinda hoping Aquaman will jump in at some point.

If you want to see what happened in my previous (and only) coco grow, look HERE: https://www.thcfarmer.com/threads/explosive-growth-in-coco-coir.136487/
I'm not going to rehash what happened in this thread when you can simply look in the old one. There are LOTS of pics and comments there. I'll say this, I got a nice crop from the last grow.

Now I'm trying to understand what happens to plants in flower, in coco, relating to salts build-up. I tried to follow both Aquaman and Cocoforcannabis recommendations for watering and feeding schedules, and that includes at least 20% runoff with each and every watering. My waterings were very frequent, up to 7x per day (every 2 hours, plus one at night) in full flower.

So again, here is the gist of it. Before flowering my plants sucked in all the nutes I gave them, and my output EC was typically 300 units smaller than input. After flower, that reversed, and the longer the plants flowered, the higher the runoff EC became even as I was reducing the overall amount of salts. At one point my input was 1000, but my outflow was 2000!

Here is the question: Why did the outflow EC continue to rise higher than the input even with 7x daily waterings with runoff amounts that were about equal to 80-90% of the input? It seems impossible that I could water at EC 1000 with lots of runoff, then repeat that 5 more times before the lights went out and at the end of that my runoff EC was higher than it started in the morning?

I'm not looking for a fix until I understand the cause.

Or - if I simply can't get a cause - then I'll try some fixes. I have an issue with the idea of feed-flush-feed-flush (which I think is a good idea to try) because I'm running a drain-to-waste feeding system with a 30 gallon bucket of nutrient solution. I'd almost have to engineer a second system running in parallel. And I don't think everyone else is having this issue, so I'm trying to understand what's going on.

It’s gonna be hard for someone to swoop in and say yeah that’s your issue. There are so many different factors that come into play. If your environment isn’t dialed in then it’s gonna be harder to dial in your nutrients. I would recommend you try a lower EC in and that may help. Each nutrient is different depending on if your running a base nutrient or if your switching nutrients at flower. It’s gonna take some trial and error on your end to figure out the issue.

 

[phxazcraig]

I'm not asking to troubleshoot an issue that hasn't happened yet. I'm looking for the technical reasons runoff EC goes up even with 20% runoff and frequent feedings. I can only figure evaporation as the cause of an EC increase, which seems impossible considering the amount of runoff I had going on. Do plants themselves push salts out of the roots?

 

[Fromunda506]

The reason she continues to accumulate salt the more food you flush through her is because she is not taking all of the nutrients out of each feed. She is drinking the water, using all the nutrients she can, and leaving the remaining salts in the coco. So each time you give her nutrients at that level, you are increasing the amount of residual salt. At least in my set up, 1000 ppm is very high and will cause buildup. Everyone’s system is different, but it sure sounds like what you’re describing. Good luck getting it sorted out. You’ll be a better grower on the other side of it. Cheers

 

[GrimReffer]

I'm not asking to troubleshoot an issue that hasn't happened yet. I'm looking for the technical reasons runoff EC goes up even with 20% runoff and frequent feedings. I can only figure evaporation as the cause of an EC increase, which seems impossible considering the amount of runoff I had going on. Do plants themselves push salts out of the roots?

@Fromunda506 is correct and plays into exactly what I was saying. You feed the plant and the amount of nutrients your plant can use is dictated by your environment.. so if your environment is not dialed in your plant are not uptaking the full amount of nutrients that they could if proper environment is maintained. So the plant only uses what the environment allows it to leaving salts behind causing salt buildup. Which is why I recommend using less nutrients for your next grow and see if that fixes your issues. This is why Joe blow a 1000 miles away could be using the exact same nutrients and growing media as you and have completely different results cause humidity temp and lights all dictate nutrient uptake.

 

[tobh]

The reason she continues to accumulate salt the more food you flush through her is because she is not taking all of the nutrients out of each feed. She is drinking the water, using all the nutrients she can, and leaving the remaining salts in the coco. So each time you give her nutrients at that level, you are increasing the amount of residual salt. At least in my set up, 1000 ppm is very high and will cause buildup. Everyone’s system is different, but it sure sounds like what you’re describing. Good luck getting it sorted out. You’ll be a better grower on the other side of it. Cheers

This.

Eventually the situation could get to the point that the solution in the media is so heavily charged with EC the plant won't even uptake water anymore. This is why "flushing agents" are an isomeric solution -- they retain the water pressure of a standard nutrient solution while introducing sugars that help the plant mobilize nutrients within their cells. The science behind it is available with a google search. Granted, run-off EC is damn near useless as a metric ime. The only real way to know what's going on in your media is with a slurry test.

When I was strictly in coco, if I saw steadily increasing EC, I would do as recommended and drop input by 20%. If it was super high (2.5+) I would flush with 1/4 strength solution until runoff ran clear and was the same EC as input. Then, immediately follow with a 20% reduced feed EC. This tended to correct issues most of the time. Even when I'm keeping mother plants around now, I do so in coco as keeping RW kosher for mother plants is more a PITA than I'm willing to deal with when running a tent full of RW. I hardly ever see these kind of problems and I don't take care of coco plants as well as I should. My typical feed EC never exceeds 1.0 unless I'm pushing for lots of new growth then I might peak over 1.2.

There are a lot of variables that come into play that can drive this kind of behavior in the media (pH swings or lack of, frequency of fertigations, size of fertigations, input EC and pH, plant pests/health issues, stage of growth, environmental factors, etc.) so by narrowing down and eliminating every last detail you should be able to identify the root cause as I am like you -- I don't like doing something just because someone online said "do this, it'll work." I want to understand the why it happened to begin with.

Not sure this was useful for you or not OP but figured I'd throw my two cents into the mix.