technical watering question from a noob (how dry is too dry, where is the sweet spot?)

[hot_box_enthusiast]

preamble:
(using Promix HP, LED lights)

in trying to learn a lot about my plants and the art of growing, I've taken to daily weighing and monitoring through veg and flower of a number of different strains. each day, when the lights come on I weight the plants. Then I water them. The next day I do the same. This allows me to calculate how much water is being lost each day (through general evaporation of the media, and plants 'drinking' the water).
if all my "research" of the past few months has taught me a few relevant things about growing cannabis for noobs they might include
1. noobs are prone to OVERWATERING their plants
2. plants want to get nice a dry before watering again

by weighing my plants daily I've been able to dial in on this a bit.

For example #1 - since I knew what the weight of a pot with media would be when bone dry, I could bring my plants close to dehydration and observe their physical reaction. At first the lower leaves become softer. A couple times I've purposely pushed a plant an extra day just to 'see'.

For example # 2 - I've also been able to observe the effects of over watering. For example; let's say I have two plants (A & B) that are each bone dry at 200g, and fully saturated at 550g. Assume the plants are the same size and health. Lets assume one difference which is that their watering cycles are out of sync. IF plant A weighs 250g (so its getting close to dry) and plant B weighs 350g (so its been more recently watered)... I wanted to get these plants "in sync" so I water them BOTH to saturation (so plant A gets 300g to bring it to 550, and plant B gets 200g to being it to 550)... the goal is now they should both weigh 550 and continue in sync. It doesn't work because plant B wasn't allowed to dry enough... when I weigh both these plants the next day, plant A will have drank more.

For example # 3 (related to #1 & 2) - If I push a plant TOO far, then it doesn't drink as much the next day. Assume plant C is bone dry at 200g, and fully saturated at 550g. Assume plant C drinks 100g per day.
scenario a) - if plant C weighs 250g... then it is NOT yet totally dry. BUT if I wait until tomorrow to water, then today it only drinks 50g (its bone dry at 200g) AND when I saturate it tomorrow, it ALSO won't drink 100g yet (it needs that day to recover)
scenario b) if plant C weighs 300g... then it is even FURTHER from being totally dry. If I let if drink 100g until tomorrow... this would be the perfect scenario. It drinks as much as possible, then tomorrow just as it dries out, it gets more.
scenario c) if plant C weighs 325g... now this one is easy... it just needs another day.

SO MY QUESTION (finally)// Where is the sweet spot between scenario a) and b) and c)?
a) seems clearly bad. even though the plant gets "bone dry" it seems to suffer by missing out on its 100g per day feed
b) would be great, but life doesnt work like this.

So if I weighed plant C and its 275g what do I do? What if it weighs 250g? Do I let it suffer the effects of not gettings its maximum 100g per day drink? Do I top it up to 300g so that tomorrow morning it needs a full feed?

I know I am deep in the weeds here, but this is the kind of questions that interest me to answer.

 

[quirk]

5 gal. Airpots
Dry weight = 11 lbs.
Wet weight = 19 lbs.
I water when I hit 12 lbs. and never go above 18 lbs. This is my sweet spot and prevents watering too OFTEN related problems. K.I.S.S.

 

[JCGreen81]

You’ll want to take all of your funding to date and meet them all in the middle so you never are dry nor too wet. You have enough compounded data to weigh this.

your plants will tell you for the most part. So will the weather man/sun.

you seem to have a good groove

 

[Oakiey]

Looks like your overthinking this.

Best time to water is the day before they start going down

 

[Mak'er Grow]

With so many variables with unknown values you will never get an exact time period for watering...so many things factor in...as it grows it will consume more and depending on climate and so much more its almost impossible to be exact.
Thats why most growers will say when its not praying to the sun/light gods then check soil with finger and check its weight and water as needed.
I my self start with adding 500-1000ml when I transplant to start and see how long it take before the plant starts to droop. From there I know to stay around that time period or a little sooner.
Best of luck and happy growin'

 

[hot_box_enthusiast]

thanks for all the replies so far!

re: "overthinking". I am down a rabbit hole because I love learning In my experience there is a lot to be learned around the margins (i.e. what is a bit too wet, a bit too dry, etc). I want to be clear that I have no intention of forever weighing every plant every day, and to emphasize that I am combining the numbers with LOOKING and feeling and then taking photos and reading about the plants. I am trying to learn more by paying close attention - so don't worry - I don't think I can (nor want to) calculate an "optimal watering" number but I want to learn it by doing // hope this stoney rambling made sense. Also... over thinking for some is what makes it fun for others

another stoney aside - another think I've emphasized learning though this analysis... I popped two packs of seeds at the same time, but transplanted one pack into 3.5" square pots and the others into 2.5" deep pots. I knew that I had to be careful not to overwater especially with the 3.5" pots that hold more media so I couldn't just "saturate" as they would take too many days. long story longer - by carefully knowing each day how much I was adding to each, and measuring to the mm each input I could understand the difference between these pots. fwiw I am sure you can learn these lessons without weighing everything

one actual outcome I've employed so far; in the 2.5" pots, they are dry at 200g and the bigger plants drinking 100g per day. So right now my rule for that batch is simply "if weight <300g then add volume up to 400g (which at drinking 100g per day means they have at least one more day before needing it again). This is what led me here. I have learned through researching growing that plants actually respond positively to stressors (add some stress, plant grows even more vigor). That is why I thought that maybe I am better to let the plants dry right down (like my rule could be if weight <250g then water... which means a plant weighing 260 wont get water that day, and will be more thirsty the next day) because the plants will come back even more. I hope that made sense to someone That is the deeper nature of my "where is the sweet spot" question... to know how much "drought stress" is *ideal*.

cheers!

 

[furnz]

Soak the container through when they feel about 25% water weight left.
Bone dry is bad for 'soil life' and can over concentrate nutrients in soil-less mediums. It will also yellow leaves prematurely, even before wilting.
Avoid just giving them a little water here and there, soak through or dont water. Trying to 'top off' a container with water is how you run into overwater symptoms. If it hasnt reached the 25% water weight left threshold, than leave it alone.
If you cant soak without the fear of staying too saturated, than you transplanted to a container too large.
Basically aslong as your not getting bone dry or watering a container with lets say 50% water weight or more, you'll be fine.

 

[DarthVaper84]

thanks for all the replies so far!

re: "overthinking". I am down a rabbit hole because I love learning In my experience there is a lot to be learned around the margins (i.e. what is a bit too wet, a bit too dry, etc). I want to be clear that I have no intention of forever weighing every plant every day, and to emphasize that I am combining the numbers with LOOKING and feeling and then taking photos and reading about the plants. I am trying to learn more by paying close attention - so don't worry - I don't think I can (nor want to) calculate an "optimal watering" number but I want to learn it by doing // hope this stoney rambling made sense. Also... over thinking for some is what makes it fun for others

another stoney aside - another think I've emphasized learning though this analysis... I popped two packs of seeds at the same time, but transplanted one pack into 3.5" square pots and the others into 2.5" deep pots. I knew that I had to be careful not to overwater especially with the 3.5" pots that hold more media so I couldn't just "saturate" as they would take too many days. long story longer - by carefully knowing each day how much I was adding to each, and measuring to the mm each input I could understand the difference between these pots. fwiw I am sure you can learn these lessons without weighing everything

one actual outcome I've employed so far; in the 2.5" pots, they are dry at 200g and the bigger plants drinking 100g per day. So right now my rule for that batch is simply "if weight <300g then add volume up to 400g (which at drinking 100g per day means they have at least one more day before needing it again). This is what led me here. I have learned through researching growing that plants actually respond positively to stressors (add some stress, plant grows even more vigor). That is why I thought that maybe I am better to let the plants dry right down (like my rule could be if weight <250g then water... which means a plant weighing 260 wont get water that day, and will be more thirsty the next day) because the plants will come back even more. I hope that made sense to someone That is the deeper nature of my "where is the sweet spot" question... to know how much "drought stress" is *ideal*.

cheers!

With your attention to detail you should skip soil and go straight to hydro. You’re suited for it lol