Precision Irrigation - learn to crawl before you walk

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Heyho Friends!

Long time Lurker here!

Learned a lot about hydroponics and sealed rooms here and on the archived overgrow.

About 6 years ago i took the leap and went from growing in tents to closed environment myself.

I had a little opticlimate 3500, a few cmh lamps and boy; was it a struggle... getting the air dialed in was a hustle and i made many mistakes. In the beginning i couldnt hang all lamps bc the electric installation crapped oit on me.

So the compressor of the ac unit ran for a minute, was off for a minute and so on until it got stuck after only a year and a half of use. So that was to change, and without cooling your grow room gets pretty baked with hid lamps...

Also i had some serious construction errors. For example; i insisted on laying tiles. Which was nice for the walls but laying tiles on wooden flooring is... well not the best choice. Wood moves and tiles just shouldnt. So the floor was covered in cracks and every sip of water that got spilled in there soaked into the wood below. Beautiful. At some point i even had shrooms come out of the cracks of the tiles. Yikes.


But none of this turned me off; i was eager to control environments and with my little setup i learned about the right dehum capacities, VPD, air handling and many more.

And, at least back then i thought, i was crushing it..

Super sticky buds and consistent flavor year round was my mission and for a while it seemed like i acieved.

But my room being only 4m² large and spiked with building flaws i always planned for the next room.

And the opportunity came this summer for a brand new room in a 50m² building made from shipping containers.

Im writing this thread as some sort of journal. I will post my grows and tries here and hope we learn together and become friends.

And as farewell heres a picture of the view my plants had in that fucked up little project of mine.

 

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So after that little teaser into the world of plant peoduction i was hooked. All i can think about is providing the perfect environment for my babies. Not for i want to care for them. This is a selfish endeveaour. I LOVE being god. I like being in control. And with technology at my disposal i sure can have my best swing at it.

So i packed up my little AC and my Dehu, and bought some LED and a Trolmaster set.

At the new location i had more space and better workflow. Heck i even buried 2 1000l pallet tanks as reservoir for the 2 rooms that are planned.
The container itself is insulated and in addition i put panel walls of walk in freezers for ease of clean of the rooms.

I attached all pictures i have of the build. I'm really not good at documenting what i do.

What might be the reason??

On the last pic there you see the first crop already moved into the construction site.

Not the best move but i had no other option.

 

[Gruendaumen]

So i started my grow. I am growing smokable CBD Flower. And because i lost all my genetics due to a ruffle with the authorities i had to phenohunt again. So i threw in 4 different strains.
Already not the best idea itself but paired with switching to LED i was flying totally blind.
Plants looked horrible for the first like 7 weeks. I vegged them for 4 weeks, hoping to improve them but to no effect.

In hindsight the problem was obvious. 2.5EC is just too low. Never thought i would say that sentence but here i am.

When i had nothing to loose and was flipping the first and very horrible looking plants on my new facility to flower i stumbled upon crop steering. Precision irrigation to be precise.


And what i read made at least as much sense to say fuck it they cant get worse. So i started to feed 3.5EC and only feed a little with huge drybacks in the first part of flower.

Plants responded great, they looked like d21 on d10 it was very irritating.

But it scratched my itch of wanting to be in control.

I stumbled through that run because all was already gone when they didnt recover during veg but i read, learned and came up with a plan.

Next run i will be utilizing P1 and P2 irrigations on rockwool slabs, and, because i cant afford them yet im going to work without sensors.

And so i got to work.

 

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Crop steering is a term that gets flung around quite a lot so i want to take a moment to define what i see as crop steering.

Its using different means of environmental control to illicit specific plant responses at certain points in a plants life.

In veg we often want it to have no constraints (slight caveat bc its obsly all strain dependent) and to produce structure freely. This means 30°C; no nighttime diff and a VPD of 0.8-1 kPa

When we flip to flower we want to simulate drought stress, even though theres ample water around. We do that by irrigating in a certain way. We prolong the delay from one irrigation to the next after we reach field capacity to have big dry backs. This makes the substrate ec go up and the plant goes in 'panic mode', stops stretching and puts all her energy in setting on flowers.
We still run 30°C but have a good cool down at night (~5°C). VPD from 1 to 1.2 kPa

After this phase is over (beginning of week 4) we switch to vegetative steering again. We put on many irrigations and let the plant bulk on those flower sires it set during stretch phase.

Temp around 27°C with little to no nighttime diff and VPD around 1.2 kPa


And after doing that for about 2 weeks we switch to ripening. Here we simulate a little drought stress again but when we irrigate we go for ample runoff so that the EC in the media doesnt get out of control.

Here we gradually lower temps as qe please. I like to go down to 23°C daytime 20° night and VPD of ~1.4 kPa

In an ideal world we now just take out all nitrogen out of our feed and run 2.5EC all the way to harvest. That way we dont starve the plant of calcium and avoid a lot of bud rot.

 

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So heres my next run to implement the irrigation strategy.

Its my first time on rockwool slabs. I vegged ~60 Sour Chem Seeds from Oregon CBD for about 3 weeks off site.

A day before transplant, i loaded the slabs full of nutrient solution and let them wick it all up over night.

Then i turned on the heating to condition the room and went to bed.

 

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The next day i brought in the young plants, already topped twice in veg.

I dipped/drenched them in a mixture of fungizides and acaricides and set them on the slabs.

First section of irrigation strategy is rooting in. Here i give 1-2 very small shots (~40ml) per plant. Just to draw oxygen into the media and thus promote root growth. I dont want to go back to field capacity for a few days so input of water should be lower than what is lost through evapotranspiration. Here is where substrate sensors come in handy because weighting rockwool slabs is an unpleasant and unprecise endeavour.

Before i go on i want to explain a few important terms; field capacity is basically just the amount of water any given substrate can hold. If you irrigare any pot it soaks up the solution until it is saturated and runoff occurs. The volume of water that gets held back is the volumetric field capacity.

Dryback is almost self explanatory. In our instance when we speak of dryback we mostly always speak of the dryback that occurs over night. This one is the biggest and hence the most important one to steer our media ec in a certain direction.
Shot size is the size of a irrigation events. Its often provided as % of a given media vol. So a 40ml shot in a 4l media is a 1% shot.

During veg steering we use 1-3% shots with small drybacks, during generative steering we use 4-8% shots with large drybacks.

Generative steering is the term for the simulated drought stress in stretch i spoke about above.

 

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So the plants are moving fast, they seem to like their new home.

They put on about 5cm a day and its time to think about an irrigation plan beyond rooting in. For now all i do is with a growwater timer from g-se. But it only can set daytime and nighttime irrigation scheduled.

With precision irrigation i wat to divide the 24hr period into 3 phases.
P1 is called ramp up and starts roughly 1.5 - 2 hrs after lights on. Here we put on a few very small shots to go back to field capacity after drying back over night. This has to be done by multiple small shots so that channeling does not occur in the substrate. P1 lasts for 1-2 hours.

It turns over into P2 which is called maintenance phase. Its supposed to maintain a certain field capacity. It is widely used in veg steering but in generative we may want to skip it, depending on substrate/plant size ratio.
P2 lasts until 1.5-2 hrs before lights off and turns over into P3

This is the dryback phase where we want the substrate to dry out slowly but only until a set water content as overdrying especially rockwool can be devastating.

So i need a controller to do that for me. Because i cant afford to invest in a growlink or aroya setup yet and i feel im learning more when i need to make my own thoughts.

My plan was to use an arduino uno and a relais to switch a pump on and off.

And with todays technology even a never-have-written-a-line-of-code human like me can do such projects.

I just turned to chatgpt with what i want my arduino to do and it shat out the code i needed in not even 30s. Chilling.

So all there was to do is a little troubleshooting with the AI Overlords apologetic help and off we go.

Then i souced an old growwater timer's casing and the potentiometers for my project è voilà; finished is the DIY Phasic Irrigation Controller for the cheaps. If anybody wants the code or more detailed photos im happy to provide, just dm me or something...

With the left two knobs i can now control event duration and interval of P1, with the right two knobs those of P2.

I will install the new piece of tech probably on wednesday after ive tested it a bunch more...

You just never know with the irrigations...

 

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So now that we are up to date here i will do my best to write an update at least every sunday. Probably also when something important happens.

Thanks for reading along, i hope you enjoy as much as i do and happy growing people!!

And with that, i let you off with a few pics of the current run.

 

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FUCK!!
I totally forgot to post, this is starting GREAT hehe

So the plants are moving along nicely. Good week of progress, i had an elbow on my irrigation lines burst on me, that was a bummer bc i believe i have dried back the rockwool a little too far there. I only recognized it when i was at site and they were already kind of light. No wilting or anything but with the hydrophobic properties that arise in rockwool im afraid i might have diminished my steering capabilities.

We'll see about that as we move along.
On sunday i pruned the ground floor to get some air flowing. I took another 2 cuts of every plant so that i can choose my top three to keep as mother stock after the fact.

Today they enjoy their first night of 12 hours uninterrupted darkness.
Up until now i ran 30°C straight as well as 75% rH.

Here is the time series data of my last week.

Now im starting to introduce a night temp diff.
I go 30°C day - 26 night.
And because i need my vpd to stay in check i turn down the rH at night to ~70%.
I will incrementally lower the rH over the course of the flower period to slowly move vpd in the direction of 1.4kPa.

At the moment they still get veg nutrients bc i still had so much in the res, i didnt want to throw it out. But i am already shortening the irrigation window to set up my dry backs. They get their feed at 4.5EC 5.8pH Runoff is at ~6EC and 6pH.

My irrigation controller is causing some issues still, im working on getting that implemented.

Room parameters
Temp 30/26 day/night rH 75/70 co2 1100 ppfd 1000

 

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So im a little early today but something bad happened...

About half of the crop (maybe more) is throwing out anthers.

So thats sad.

Straight up hermed..
i doubt its something wrong with my setup but im open in getting my mind changed if someone here would want to chime in?
Its not in a particular spot, they are spread through the room. I didn prune extremely hard but maybe that was a trigger?
Theres nothing wrong with light schedule. Two days ago I did go in 3hrs after lights out to apply IPM spray but they had over 8 hours of dark after i was finished and ive never seen a whole crop herm after such a miniscule event, did you?
There was no other equipment failure or a comparable event i.e. that temps were extremely high or something...

Im completely baffled...

Air parameters were 30°C and 75% rH straight during veg with 600-700ppfd and 800-900ppm co2.
At first day of flower i cranked light to 1000ppfd to make up for the dli loss when flipping and set co2 at 1200 ppm.
I also introduced a slight temp diff of 4-5°C and lowered rH during night to keep vpd at ~ 1.1.

So i really doubt its some environmental factor those values are as good as ive ever had them but i never had such a hermed out crop...
Strain is sour chem of oregoncbd. Its Chem4 on GG#4 conversion (somehow they transitioned their GG#4 from THC to CBD dominant or something)

maybe any of you have ideas on how that herming happened?

Cheers