How much water does soil hold?

[Emilya Green]

I got curious last night as I watered my babies in their solo/beer cups, and after slowly watering to the point of run off, I weighed my cup. I was shocked to learn that the previous light as a feather cup now weighed almost a pound, or 418 grams to be exact.

I was shocked, so I decided to find out how much water I just added. I carefully weighed a cup full of dry soil and took that off of the total. I then weighed out the resulting 320 grams of water.

Here is a picture of how much water that really is:

That my friends, is a lot of water to be suspended in the soil. Now it is clear how the micro life moves around inside of the root ball. It really makes a difference to water completely and thoroughly.

Weighing these beer cups to find out how much water has been used is also a very valuable tool in the veg tent. When I am baked and watering, sometimes the "lift" method is less than accurate. Weighing takes away any doubts as to when it is time to water and which plants are using more water than others. For example, my most robust plant just used 63 grams of water in the last 18 hours, compared to my smallest plant which only used 20 grams in the same period of time. Being able to see exactly what is happening inside of that cup, knowing which plants are using or not using water, is a huge advantage in accurately judging when to water and when to let it ride, and to recognize when a problem is occurring.

 

[DRM Ranch]

I'm fairly surprised there are no comments on this, so I'm happy to be the first.

Do you plan to continue taking weights, and will you be tracking them in some way?

DRM Ranch

 

[Faic]

Water weighs a bit over 8lbs/gallon. Or over 3700 grams.

Sorry, but I can't help but smile. You sound like you're stoned in your garden spazzing with captain obvious. And there's nothing wrong with that at all.

 

[Emilya Green]

I'm fairly surprised there are no comments on this, so I'm happy to be the first.

Do you plan to continue taking weights, and will you be tracking them in some way?

DRM Ranch

Hi DRM, yes I too was surprised... it is getting plenty of notice in the other places that I hang out. I have indeed found the usefulness of a scale in the grow room and have found that my "lift method" is less than accurate sometimes, especially when I am stoned. I now am double checking myself with a quick check on the scale. I have also found that I can accurately see how much water is being used each day, not that the usual visual indications were not showing me that already, but it is a good double check against myself. Moving this beyond the solo cup stage however is going to be problematic since I really don't want to buy a special scale just to weigh 1 and 5 gallon containers.

Water weighs a bit over 8lbs/gallon. Or over 3700 grams.

Sorry, but I can't help but smile. You sound like you're stoned in your garden spazzing with captain obvious. And there's nothing wrong with that at all.

Yes, Captain Obvious stands over my shoulder quite often Faic, but that keeps me honest, especially when I am working while stoned. The point in doing this however is not quite as obvious. First, I think that many people lose sight of how much water is actually suspended in their soil when they water to the point of saturation. This is important in two ways... first, the ability of properly pH'ed water to totally change the soil pH, and second, making it obvious how it is that the protozoa and all the others in the micro herd, migrate all throughout the root ball. With this much water in there, it becomes clear that they are simply swimming around.

 

[Faic]

Emilya, don't take this the wrong way please. I'm not busting your chops or anything, I just find it kind of adorable if that's not being too bold.

With how much you're geeking over the weight of water and hydrodynamics in a soil garden, I would love to see how you'd be with a hydroponic grow...

Being a bit more on the serious side, yeah I can totally relate to how details in a soil grow shed light on things, my soil grow was a nightmare. And I'm cutting her in about 10mintues

 

[Calvados]

Stupid question. How do you allow for the growth of the plant and it's retention of the water when you are weighing?

 

[Emilya Green]

Stupid question. How do you allow for the growth of the plant and it's retention of the water when you are weighing?

actually, a pretty good question. I do this by allowing 50-75 grams of weight above what dry soil weighs to the point that I decide the water level is low enough to water again. It's not exact science, but it gives me a reference to work with.

 

[Calvados]

actually, a pretty good question. I do this by allowing 50-75 grams of weight above what dry soil weighs to the point that I decide the water level is low enough to water again. It's not exact science, but it gives me a reference to work with.

It sounds very reasonable to measure dryness that way for seedlings, but for veg and flowering it sounds iffy to the point that picking up the pot would make more sense.

 

[Emilya Green]

yes indeed... and shortly after the solo cup stage, my little postal scale will not handle the weight and I have to rely on the lift method. After a while you get very good at judging by weight just by picking them up, and this is no longer an issue. These days, I simply have to walk in my bloom room and glance at the leaves... and I can tell whether it is time to water or not.

 

[Lerugged]

So outdoors if they were growing wild they would be getting different amounts of water each time it rains. Possibly your less than super accurate lifting method is more in line with a natural grow. Just a thought. You soil might have some items that hold more water than others. Humans try tot be super accurate most of the time where nature isn't. Pretty interesting post though.thanks emylia

 

[PistolPete80]

So outdoors if they were growing wild they would be getting different amounts of water each time it rains. Possibly your less than super accurate lifting method is more in line with a natural grow. Just a thought. You soil might have some items that hold more water than others. Humans try tot be super accurate most of the time where nature isn't. Pretty interesting post though.thanks emylia

While true, natural does not equal optimal. Most of us are tying to optimize whether for size, quality or other reasons. Thanks for sharing the info Emilya as always!