Using a water meter for cannabis

fawnridge · Mar 20, 2023

Got this water meter yesterday and I have a few questions about using it.
1. How deep into the soil should you check?
2. What should the meter read a) the day after watering, b) the day that water is needed?
3. How accurate is this meter?
Thanks and a tip of the hat.

Habosabin · Mar 20, 2023

I'd go down like 6 inches. These work well to train you into watering correctly. Once you get the hang of it you won't need it. It just depends on the size of your container but you don't water until it's hitting the red. Lift the pot when it says its low to get a feel of the pot. Then lift it when it says its saturated. then you will know your range.

fawnridge · Mar 20, 2023

Habosabin said:
I'd go down like 6 inches. These work well to train you into watering correctly. Once you get the hang of it you won't need it. It just depends on the size of your container but you don't water until it's hitting the red. Lift the pot when it says its low to get a feel of the pot. Then lift it when it says its saturated. then you will know your range.

Right now, the seedlings are in 1-gallon nursery cans. 6" brings the probe almost to the bottom of the pot. Is that where you are suggesting I measure? What happens when I move them up to 3-gallon cans? Still 6" or to the bottom. Thanks!

Habosabin · Mar 20, 2023

fawnridge said:
Right now, the seedlings are in 1-gallon nursery cans. 6" brings the probe almost to the bottom of the pot. Is that where you are suggesting I measure? What happens when I move them up to 3-gallon cans? Still 6" or to the bottom. Thanks!

Try going to the middle of the pot to lower 3/4. Somewhere in between should be fine. Good luck.

Oldchucky · Mar 20, 2023

They make them with 12 inch probes. If they made longer ones, I would get one of them. From experience, dry means bone, dry, moist means kind of dry, and wet means moist, on mine. You can check it with soil a varying degrees of moisture and see when it reads Before you use it on your pot plants. Kind of like calibrating it. Not the most accurate things in the world but what do you want for less than 15 bucks.

Oldchucky · Mar 20, 2023

Comfortably numb posted a resource called, new, simplified way of watering. Or something to that effect, that deals with using them in cloth pots. I don’t know how to link stuff, but maybe someone else can come up with it. It’s informative.

fawnridge · Mar 20, 2023

Oldchucky said:
Comfortably numb posted a resource called, new, simplified way of watering. Or something to that effect, that deals with using them in cloth pots. I don’t know how to link stuff, but maybe someone else can come up with it. It’s informative.

I read that earlier today. These seedlings are going outside in mid-May, so they'll get moved up to 3-gallon cans on April 1st, but still in the house.

steamroller · Mar 20, 2023

I drilled holes 1/4 , 1/2 , and 3/4 up my 5 g pots on 2 sides
I would check multiple levels from both sides if needed.

New Simplified Way to Water Marijuana Plants

To know if you need to water your cannabis plant get yourself a soil meter. Poke or drill 4 holes in your pot 1/4 way up from the bottom spaced around the pot...

www.thcfarmer.com

MIGrampaUSA · Mar 20, 2023

Habosabin said:
I'd go down like 6 inches. These work well to train you into watering correctly. Once you get the hang of it you won't need it. It just depends on the size of your container but you don't water until it's hitting the red. Lift the pot when it says its low to get a feel of the pot. Then lift it when it says its saturated. then you will know your range.

I disagree on the part where you're saying "when you get the hang of it you won't need it." I consider using the moisture meter as an "SOP" (standard operating procedure) for the soil grower. The lift to see if it's light method does work but its ambiguous where the moisture meter gives consistency.

So yes, even after all these years I still use and recommend others use a moisture meter. Just my 2 cents. lol

Edit: We water cannabis when the meter reads around 2-3. Usually about every 3-4 days.

Habosabin · Mar 20, 2023

I use a meter as sop in my rockwool. It's wireless and works really well once calibrated. This one works in soil as well. Since I don't check daily all the time these are good.

Habosabin · Mar 20, 2023

What's cool about the one I just posted is it can connect to a wireless weather station and you can see from your phone from anywhere when you need to water. My pumps are wifi too so I remotely water.

MIGrampaUSA · Mar 20, 2023

Habosabin said:
I use a meter as sop in my rockwool. It's wireless and works really well once calibrated. This one works in soil as well.

Nice! I've been contemplating buying the Pulse Grow Hub when its released in April. It looks pretty robust in what all it can do (it even has a soil moisture sensor) but it's quite expensive and duplicates other purchases I've made. What's nice is all the data is in one place where what I have now is in several different phone apps.

What's not nice about it is its pretty expensive!

Habosabin · Mar 20, 2023

MIGrampaUSA said:
Nice! I've been contemplating buying the Pulse Grow Hub when its released in April. It looks pretty robust in what all it can do (it even has a soil moisture sensor) but it's quite expensive and duplicates other purchases I've made. What's nice is all the data is in one place where what I have now is in several different phone apps.

What's not nice about it is its pretty expensive.

Yeah. I'm on a budget. One grower here had a really nice automated product that watered once his sensor hit a threshold but it was around $700 for one sensor and controller. I would love automated ph too.

MIGrampaUSA · Mar 20, 2023

Habosabin said:
Yeah. I'm on a budget. One grower here had a really nice automated product that watered once his sensor hit a threshold but it was around $700 for one sensor and controller. I would love automated ph too.

If the money spent was irrelevant I'd automate everything and have the software document it all in spread sheets. Since I'm also on a budget, and the hub itself is over $500 prior to adding additional sensors ...

We've been documenting everything the old fashioned way ... In a 5 subject college ruled notebook. I have a wireless Govee temperature and humidity sensor that records my environmental data on a graph. It even calculates VPD.

BigBlonde · Mar 20, 2023

fawnridge said:
Got this water meter yesterday and I have a few questions about using it.
1. How deep into the soil should you check?
2. What should the meter read a) the day after watering, b) the day that water is needed?
3. How accurate is this meter?

I use a meter more than any other method.

1. I push it into the soil till it's as close to the bottom as I can get it, but don't force it. If it's hard to push in you may be hitting a root, so find a new spot. One or two inches from the bottom is best. It can be informative to push it in slowly to learn how the moisture changes at various levels. Near the bottom is what matters.

2. a) It's pointless to check immediately after watering. b) The meter will tell you when to water. A day or two or three after watering is when to start checking. I usually water when the meter drops below 2, but some say lower is better. When I first started using a meter, I watched the leaves to see if they were drooping and lifted the pots to "calibrate" the meter. The meter is more accurate, though.

3. I don't believe accuracy is the goal. The scale doesn't matter. Reliability is what is important. By that, I mean we want the meter to do what it does the same way every time it is used. It doesn't matter if I need to water when my meter reads a 2 and yours reads a 1 on their respective scales. It only matters that each meter tells us reliably when we need to water. We know that by learning how to read the meter relative to the needs of the plants.

MIGrampaUSA · Mar 20, 2023

BigBlonde said:
I use a meter more than any other method.

1. I push it into the soil till it's as close to the bottom as I can get it, but don't force it. If it's hard to push in you may be hitting a root, so find a new spot. One or two inches from the bottom is best. It can be informative to push it in slowly to learn how the moisture changes at various levels. Near the bottom is what matters.

2. a) It's pointless to check immediately after watering. b) The meter will tell you when to water. A day or two or three after watering is when to start checking. I usually water when the meter drops below 2, but some say lower is better. When I first started using a meter, I watched the leaves to see if they were drooping and lifted the pots to "calibrate" the meter. The meter is more accurate, though.

3. I don't believe accuracy is the goal. The scale doesn't matter. Reliability is what is important. By that, I mean we want the meter to do what it does the same way every time it is used. It doesn't matter if I need to water when my meter reads a 2 and yours reads a 1 on their respective scales. It only matters that each meter tells us reliably when we need to water. We know that by learning how to read the meter relative to the needs of the plants.

The only thing I do differently is I take my measurements in 3-4 areas of the pot and mentally calculate the average.

It's the consistency/reliability that matters just like @BigBlonde said. This stands true in many areas of cultivating cannabis. Watering habits is just one of them.

RootsRuler · Mar 20, 2023

I have a 4 in 1 probe like the ones you have and I find the moisture meter worthless. As oldchucky noted, they don't really reflect what is happening as the readings depend at what soil horizon point the probe is sitting at at the time. I've watered pots thoroughly and have stuck the meter in the soil only to have it come up as "dry".

I use mine mainly for soil PH. I've been using light pot method without fail.

MIGrampaUSA · Mar 20, 2023

RootsRuler said:
I have a 4 in 1 probe like the ones you have and I find the moisture meter worthless. As oldchucky noted, they don't really reflect what is happening as the readings depend at what soil horizon point the probe is sitting at at the time. I've watered pots thoroughly and have stuck the meter in the soil only to have it come up as "dry".

I use mine mainly for soil PH. I've been using light pot method without fail.

I also have a 4-in-1 probe. I don't use it. I don't really trust any of the readings on the one I have. It wasn't expensive and sometimes you get what you pay for. I do trust my analog moisture meter. I have 3 of those. They are all 0-10 like the one the OP posted and they are measuring pretty much exactly the same.

As for what's going on in the soil, it's important to take more than 1 reading. We use 3-4 readings and average it. This has worked well for us.

RootsRuler · Mar 20, 2023

MIGrampaUSA said:
I also have a 4-in-1 probe. I don't use it. I don't really trust any of the readings on the one I have. It wasn't expensive and sometimes you get what you pay for. I do trust my analog moisture meter. I have 3 of those. They are all 0-10 like the one the OP posted and they are measuring pretty much exactly the same.

As for what's going on in the soil, it's important to take more than 1 reading. We use 3-4 readings and average it. This has worked well for us.

I like the Ecowhitt probes Habo posted and would love to automate the watering using moisture probes. Just not sure how reliable and/or accurate they are in respects to using them to automate watering. If they misread and overwater or underwater they sort of kill the whole reason you used them in the first place. Coming home to a tent floor full of water is no bueno.

What I love about using these types of probes is that it would customize the feed frequency to the individual plants needs which is always a plus. I wish I could feel more confident about them. I'm sure someone is either launching or in development of one of these types of systems so I'm going to keep using my light pot method but when one does come out that is reliable and proven I'll definitely jump on it as I frequently have to leave for extended periods of time for work leaving my girls unattended. I have a crude auto irrigate system that works but would love something like this.

The pulse system looks promising. What have you heard about it? I wonder if it would be compatible with the ACI system?

BTW...is that $37 for EACH probe and display?

BigBlonde · Mar 20, 2023

MIGrampaUSA said:
The only thing I do differently is I take my measurements in 3-4 areas of the pot and mentally calculate the average.

I do something like that. I just forgot to mention it. I move the probe around as the soil gets drier and as it's closer to watering day. I worry somewhat about damaging roots and the possibility of them being infected or otherwise harmed. So I try to find the middle ground (pun intended).

Using a water meter for cannabis

Using a water meter for cannabis

fawnridge

Habosabin

fawnridge

Habosabin

Oldchucky

Oldchucky

fawnridge

steamroller

New Simplified Way to Water Marijuana Plants

MIGrampaUSA

Habosabin

Attachments

Habosabin

MIGrampaUSA

Habosabin

MIGrampaUSA

BigBlonde

MIGrampaUSA

RootsRuler

MIGrampaUSA

RootsRuler

BigBlonde

Privacy & Transparency

Privacy & Transparency