Does inadeqaute watering effect yield?

This might be a no-shit Sherlock kind of thing but I haven't found any posts on RIU or through google that ever told me about the following:

Is it possible to under-water to the point that yield is decreased without the plant showing any obvious signs that it is under-watered?

I have been growing for a little over a year and always thought I was watering my plants properly. I take the warning to avoid over-watering very seriously and so I wait until the pots are very light but never to the point that the plants wilt or show any obvious problems. On all my grows the buds seemed to stop swelling at week six or so and I thought this was the normal grow cycle.

My current grow is the first time I considered the idea that this stalled bud development could be due to under-watering. This time when the buds first started to noticeably stall I decided to increase the frequency and amount of water. This ended the stalling and the plants are showing much larger buds compared to all of my previous grows.

So here is what I think I've learned: When stretching has ended and the buds begin to pack weight the plant consumes more water. Growers need to increase food and water at this time. When to increase is plant/strain dependent but usually around week five or six of flower.

Who else has seen or experienced this sort of thing?

I stopped using a water meter many years ago... They get watered when they start to wilt - On that day they bounce back an hour after watering. Nature doesn't always drop water on a plant when it needs it. Just have a feeling it may strengthen the plant to let it get in a full cycle of intake/out-take.

I can't speak for everyone, but personally, as the plant gets larger an starts producing buds I always increase my feeding. An example would be in 1 gallon pots watering week 1s id water 4-5 times a day. But now in the 6th week of flower I'm flooding my table twice a day, everyday.

My advice would be is to really nail your ph. Increase your watering, and just keep a close eye on your plants. You'll learn what they like

I believe you are correct, that plants can use more water than they necessarily get- and any inadequacy in the supply will adversely affect yields.

This core belief is why I built my own RDWC system, so plants are NEVER without as much water as they want, and in fact I suspect that much of the reason hydroponics is consistently faster than soil is due to this very phenomenon at work.

SwankyDank said:

This might be a no-shit Sherlock kind of thing but I haven't found any posts on RIU or through google that ever told me about the following:

Is it possible to under-water to the point that yield is decreased without the plant showing any obvious signs that it is under-watered?

I have been growing for a little over a year and always thought I was watering my plants properly. I take the warning to avoid over-watering very seriously and so I wait until the pots are very light but never to the point that the plants wilt or show any obvious problems. On all my grows the buds seemed to stop swelling at week six or so and I thought this was the normal grow cycle.

My current grow is the first time I considered the idea that this stalled bud development could be due to under-watering. This time when the buds first started to noticeably stall I decided to increase the frequency and amount of water. This ended the stalling and the plants are showing much larger buds compared to all of my previous grows.

So here is what I think I've learned: When stretching has ended and the buds begin to pack weight the plant consumes more water. Growers need to increase food and water at this time. When to increase is plant/strain dependent but usually around week five or six of flower.

Who else has seen or experienced this sort of thing?

Click to expand...

Ok, so perhaps i'm lucky because it's relatively warm here in CA, but I've never ever, ever, seen any damage from overwatering, from a soil that retains too much water? Yes, but overwatering in a good soil mix is nearly impossible, assuming you approach it logically, when I water my plants, I flood the bejesus out of them, not all at once, and not to the degree to where the aeration "floats", the trick is to set your sprayer/hose on a single jet, if you have it on the "shower" setting it floats the perlite up like mad, and the soil tension doesn't allow it to be fully absorbed. The jet setting helps to water them without that being an issue.
Also if you let your soil get to the point where your plants are drooping, you are essentially airpruning the roots. Which is bad.
Cannabis likes water, but hates wet roots, so you need to make your soil media to where it keeps itself a more "humid" state as opposed to a wet sloppy consistency, that's why I use soooo friggin much aeration in my mix.
I always, always, water them extremely thoroughly.
A good quality compost with most of it being degraded leaves is a perfect thing to add for the "humidity" of the soil.
The trick is to get a good aeration mix, using as much as you can of the types that retain water, volcanic rock, pumice, rice hulls, vermiculite, biochar, etc.
Perlite doesn't work as well as the others do, vermiculite is perhaps the best.

Thanks for replies everyone.

I thought of another way to summarize:

When growing in soil It is better to err on the side of slightly over-watered rather then err on the side of slightly under-watered.

greasemonkeymann said:

Ok, so perhaps i'm lucky because it's relatively warm here in CA, but I've never ever, ever, seen any damage from overwatering, from a soil that retains too much water? Yes, but overwatering in a good soil mix is nearly impossible, assuming you approach it logically, when I water my plants, I flood the bejesus out of them, not all at once, and not to the degree to where the aeration "floats", the trick is to set your sprayer/hose on a single jet, if you have it on the "shower" setting it floats the perlite up like mad, and the soil tension doesn't allow it to be fully absorbed. The jet setting helps to water them without that being an issue.
Also if you let your soil get to the point where your plants are drooping, you are essentially airpruning the roots. Which is bad.
Cannabis likes water, but hates wet roots, so you need to make your soil media to where it keeps itself a more "humid" state as opposed to a wet sloppy consistency, that's why I use soooo friggin much aeration in my mix.
I always, always, water them extremely thoroughly.
A good quality compost with most of it being degraded leaves is a perfect thing to add for the "humidity" of the soil.
The trick is to get a good aeration mix, using as much as you can of the types that retain water, volcanic rock, pumice, rice hulls, vermiculite, biochar, etc.
Perlite doesn't work as well as the others do, vermiculite is perhaps the best.

Click to expand...

I water my plants at least once a day.

greasemonkeymann said:

Cannabis likes water, but hates wet roots, so you need to make your soil media to where it keeps itself a more "humid" state as opposed to a wet sloppy consistency, that's why I use soooo friggin much aeration in my mix.

Click to expand...

The humidity issue is another thing I'm re-visiting as most books/grow guides teach that keeping humidity below 50% is crucial during flower. For my setup, my eyes tell me that the plants are growing and budding much better with percentages in the upper 50's to lower 60's and I haven't had any mold issues. There is excellent air-flow so maybe that balances it out. I have noticed the higher humidity is directly tied to more water, probably due to increased evaporation from the pot plus increased transpiration from the plants.

Anyway, I think I have adjusted my approach to water and humidity. A little less worrying about excess moisture.

nk14zp said:

I water my plants at least once a day.

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I first really noticed this watering issue in July when temps were hitting low 80's in the canopy. I was watering every other day and it still didn't seem like enough water. My sub-conscious mind was saying give it more water this shouldn't be drying out so quickly but I was so worried that once a day would be too much. One day I finally said screw it and doubled the amount from 2 quarts per plant to 1 gallon. Somehow they still dried out in two days and the difference in growth was so visibly obvious that I increased the dose to 1.5 gallons and that seems to be the sweet spot. This is in 4 gallon containers.

Swanky,
I totally agree with your conclusions. I feel like I experienced the same issues, even down to the 6th week slowdown. More water totally helped. Like you said, it really is kind of a no-brainer.

Look at those nature shows. Its all dry and dusty. Then it rains and plants pop out all over the place. Imagine how much more the plants would grow if there was always some water around.

I would totally go with too moist over too dry. I mulch the top of my soil-filled pots with coco chunks to try to keep the moisture in.

Increasing the amount of "minerals" in my soil really helped with the 6th week slump too. The first soil mix I used included like a teaspoon of Azomite, like that stuff was precious and poisonous. I'd always have to feed plants something near the end of flowering. Then these guys convinced me to go up to 4 cups of a more diverse mineral mix per cubic foot of soil. Results have been great since then. No more soaking buckets of bat guano and kelp all over the place. The soil can carry everything through. Thanks guys!

youraveragehorticulturist said:

Swanky,
Then these guys convinced me to go up to 4 cups of a more diverse mineral mix per cubic foot of soil. Results have been great since then.

Click to expand...

Do you have a link or can you share the recipe for the mix? I would like to try it.

SwankyDank said:

Do you have a link or can you share the recipe for the mix? I would like to try it.

Click to expand...

I have the same mind set as you probably, underfeed and underwater the plants. I have to start topdressing at week 4. I am switching to a larger pot, I think that I was getting root bound in 5gal... Smaller plants until then lol.

ttystikk said:

I believe you are correct, that plants can use more water than they necessarily get- and any inadequacy in the supply will adversely affect yields.

This core belief is why I built my own RDWC system, so plants are NEVER without as much water as they want, and in fact I suspect that much of the reason hydroponics is consistently faster than soil is due to this very phenomenon at work.

Click to expand...

This is something i believe myself, hydroponics allows plants to have an unlimited water supply i think alot of people overlook this, and focus more on nutes
the plants process so much water and light through their life but only requires a tiny amount of nutes in comparison
i was running at 2.0 most of the time, i run at 1.5ec and see no difference

i take advantage of this unlimited water supply and it seems to work for me

i run my garden between 85-88f most of the time, i do not use co2 additions but i do use lots of air movement
something like 20-25% of the power of my lights with fans and extraction

when running a hot room the plants will constantly drink and constantly transpire, keeping the humidity low is essential to allow the plant to transpire into the air around it
keeping constant movement of air over the plants at all times ensures the humidity around the leaf surface is low to keep the exchange process going

this idea that plants will shut down over 75-80f indoor is not my experience

the plant will close its stomata in an effort to protect itself and conserve water. this causes the leaves to heat up and they will die quickly
i think this is a soil growers problem not a hydro one

with hydro this never happens for me, during the heat wave here my temps reached 92f, a large plant i was growing was drinking 12 liters of water every day
in the later stages of flower
i believe being able to process this amount of water though the plant with the added heat, helps speed things up

peace

@skunkd0c I agree with pretty much all of the above. One thing I've noticed this summer is that higher temps push my girls to finish faster.

As I've raised my running RH, I've noticed my girls tend to be less leathery and they do grow faster.

I raised my EC to 2.0 in response to advice from people running CDM/CMH lighting; they say the plants running under such light want higher EC than under HPS. It's working so far...

Gotta have CO² from somewhere... if the room isn't sealed, then it needs enough ventilation to get a good amount.

skunkd0c said:

with hydro this never happens for me, during the heat wave here my temps reached 92f, a large plant i was growing was drinking 12 liters of water every day

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3 gallons! That's a lot of water. How large was it? I want to start growing bigger and would like to get a feel for how much water a big plant can handle.

skunkd0c said:

i believe being able to process this amount of water though the plant with the added heat, helps speed things up

Click to expand...

I just saw this increased speed first hand. This grow is the first time the plants have finished flowering at the time stated by the breeder. With previous grows the plants seemed to be laboring to finish and I would end up chopping even though they didn't look ready. Now it is obvious they are ready. Not just trichromes but to the naked eye it is obvious they are done and it is two weeks earlier then any previous harvest.

ttystikk said:

@skunkd0c I agree with pretty much all of the above. One thing I've noticed this summer is that higher temps push my girls to finish faster.

As I've raised my running RH, I've noticed my girls tend to be less leathery and they do grow faster.

I raised my EC to 2.0 in response to advice from people running CDM/CMH lighting; they say the plants running under such light want higher EC than under HPS. It's working so far...

Gotta have CO² from somewhere... if the room isn't sealed, then it needs enough ventilation to get a good amount.

Click to expand...

The humidity thing is a complex one, in the early days folk believed that low humidity produced more resin
the plant would respond to the dry air and fight back with extra resin, i have never noticed this, i think its a myth

outdoor plants would have much higher humidity and they love it, sub and tropical plants grow in places that do not tend to be dry like a desert
so i think higher 50/60% humidity is better for the plant tissue, just as it is better for humans and their skin
hot dry air blowing on plants causes more wind damage than hot moist air, also plant growing in soil could benefit from higher humidity
as they are not able to drink whenever they like as hydro plants can

but the high humidity in my case would stop the plants being able to transpire into the air around them
as i am running a hot room with cold res i do not heat the res i try to keep them tap water cool
i add water daily with big plants its better for the DO levels

i guess it is about finding the right balance, the reason why plants grow fast in green houses is because of trapped heat and extra humidity

i lowered my ec as everyone else i talk to seems to grow on a lower ec lol, 1.3-1.5 i thought i would give it a go
i am in the testing phase so far so good,

I follow vapor pressure deficit theory, or VPD. There is an ideal range for humidity which shifts upward as temperature rises. Within this range, plants can grow their fastest because they aren't trying to keep up with moisture loss. Yes, get RH too high and they can't transpire but that's above the ideal VPD range. I'm running RH in the seventies at temps in the upper seventies/low eighties and the ladies love it.

Under watering, letting soil dry out will make yield suffer and leaves die off. . Over watering will cause root rot and dampening off and black mold. Find the happy medium your plants like. It varies from plant to plant.

SwankyDank said:

3 gallons! That's a lot of water. How large was it? I want to start growing bigger and would like to get a feel for how much water a big plant can handle.

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i grew it for 1 week under 125 cfl just to get the roots growing out of the larger 3 inch rockwool blocks
i then vegged it for 5 weeks under 600w MH ,

she flowered for 8 weeks with a 600w hps directly above and a 600w on the side. although it was sharing this other light with some more plants
so it would be fair to say it flowered with the equivalent of 900w of hps and had a total grow time from rooted clone of 14 weeks

she was bent over to 4.5 feet or so tall would of been about 7ft tall if it was not bent over
it was 3.5 ft deep and 5 ft wide and yielded 28 oz






peace

skunkd0c said:

The humidity thing is a complex one, in the early days folk believed that low humidity produced more resin
the plant would respond to the dry air and fight back with extra resin, i have never noticed this, i think its a myth

outdoor plants would have much higher humidity and they love it, sub and tropical plants grow in places that do not tend to be dry like a desert
so i think higher 50/60% humidity is better for the plant tissue, just as it is better for humans and their skin
hot dry air blowing on plants causes more wind damage than hot moist air, also plant growing in soil could benefit from higher humidity
as they are not able to drink whenever they like as hydro plants can

but the high humidity in my case would stop the plants being able to transpire into the air around them
as i am running a hot room with cold res i do not heat the res i try to keep them tap water cool
i add water daily with big plants its better for the DO levels

i guess it is about finding the right balance, the reason why plants grow fast in green houses is because of trapped heat and extra humidity

i lowered my ec as everyone else i talk to seems to grow on a lower ec lol, 1.3-1.5 i thought i would give it a go
i am in the testing phase so far so good,

Click to expand...

This whole year so far i have not used a de-humidifier nor an AC unit. It is currently 8:09pm 82% RH 78f. At 3pm earlier it was 88f in my house and the plants dont seem to mind it. I even flowered some dj short blue dreams in 80%rh 85f with no issues, i did top the hell out of them and use a screen of green though. And they did drink a gallon per plant every 3 days. However, if i throw some indica's in there they might get stretchy from the heat and that is not how i like my indica's lol