AusBonsai

Bretts wrote:There has been alot of talk in the bonsai circles that using a larger gravel(or larger grade medium) at the bottom of the pot as the Japanese have recommended is counter productive to drainage.
I was very glad that another member posted this link up as it explains what they are talking about very well.
http://bonsaiwonders-art.blogspot.com/2 ... ayers.html

If you understand this correctly it is not really counter productive to drainage. What is actually happening is it moves the water table off the bottom of the pot. I think this could be very useful in certain situations and maybe the Japanese do know what they are doing when it comes to what we call a drainage layer. Is it so bad to make the water sit towards the top of the pot rather than on the bottom.

This is what I find so amusing about alot of the advice we receive. The reality of this advice is so different than what was going around.

I am not really sure what this means as far as Diatomite goes though Grant. Keeping the grade the same as the rest of the pot but a more absorbent medium is some what different. Would be very interesting with a glass pot so we could see what happens! Maybe the water would still sit at the bottom of the pot only to be soaked up by the diatomite? Maybe the water table would just move further up the pot as when we use a larger grade at the bottom?
Who's got a glass with holes in it?

the addition of a drainage layer in the bottom of a container does not improve drainage, but merely increases the height of the saturation zone in any given container/bonsai pot and in turn, increases the water carrying capacity of the substrate rather than decreasing it. In other words, the same pot without a drainage layer will hold less water because of the height of the column of water prior to the impermeable layer (the bottom of the pot).

Bretts wrote:Hi James
The sponge illustration is very good. I think that was a quote from Brent which I read before explaining how a flat bonsai pot drains less than a taller cascade pot or even a nursery pot.
Although this guy does a great job of explaining the whole issue and even explores the advantages of using a "drainage layer" or better said as varying grades in a pot. I think he may be mistaken (and I see this suggestion through the whole article) by suggesting that a pot that has the saturation layer moved upwards by a coarse layer at the bottom actually holds more water than if it didn't.

the addition of a drainage layer in the bottom of a container does not improve drainage, but merely increases the height of the saturation zone in any given container/bonsai pot and in turn, increases the water carrying capacity of the substrate rather than decreasing it. In other words, the same pot without a drainage layer will hold less water because of the height of the column of water prior to the impermeable layer (the bottom of the pot).

Yes as is represented by the sponge if you took two pots a tall one and a flat one of the same volume the flat one will hold more water after draining. But if you add a coarse layer at the bottom of a pot and lift the saturation layer then compare it to the same pot without a coarse layer. You are in fact comparing a smaller flatter pot to a larger taller pot!
I think the smaller area here even though it is a flatter shape will actually result in less water being held when you use a coarse layer at the bottom.

Bretts wrote:Just did a test on zeolite and diatomite.
Used 100mm (500ml) nursery pots full of medium.
I graded the medium as best I could but the diatomite was slightly larger.
Zeolite dry weight 680g Diatomite dry weight 398g
Waterd each medium with 1L of water through a fine rose watering can and any that drained out was collected.
After 15 mins
Zeolite wet 755g (75g increase) Diatomite wet 524g (126g increase)
Shortly after I measured the collected run of from each pot and found that the Zeolite medium had absorbed 60ml the Diatomite had absorbed 120ml
This means the zeolite pot now holds about 12.5% water volume and the Diatomite holds about 24% water volume.

At these percentages it is hard to imagine that either mediums could be over watered when used well graded and at 100%. Within 15 minutes of watering both these mediums are in the optimum water to air ratio. Yet from these results the diatomite would be superior as it has more water storage and would stay in this optimum water air ratio longer!

Oh and two hours later the weight of the mediums has stayed constant showing that the drainage found it's balance of water tension to gravity within 15 mins of watering.

Bretts wrote:I was thinking how silly I was after wanting a glass contianer with holes and thought a plastic cup would be an esay solution
Was there any pooling in the bottom of the bottle after it drianed?

kcpoole wrote:

Bretts wrote:Just did a test on zeolite and diatomite.
Used 100mm (500ml) nursery pots full of medium.
I graded the medium as best I could but the diatomite was slightly larger.
Zeolite dry weight 680g Diatomite dry weight 398g
Waterd each medium with 1L of water through a fine rose watering can and any that drained out was collected.
After 15 mins
Zeolite wet 755g (75g increase) Diatomite wet 524g (126g increase)
Shortly after I measured the collected run of from each pot and found that the Zeolite medium had absorbed 60ml the Diatomite had absorbed 120ml
This means the zeolite pot now holds about 12.5% water volume and the Diatomite holds about 24% water volume.

At these percentages it is hard to imagine that either mediums could be over watered when used well graded and at 100%. Within 15 minutes of watering both these mediums are in the optimum water to air ratio. Yet from these results the diatomite would be superior as it has more water storage and would stay in this optimum water air ratio longer!

Oh and two hours later the weight of the mediums has stayed constant showing that the drainage found it's balance of water tension to gravity within 15 mins of watering.

This got me thinking Brett, and also our comment about having a glass jar with holes in it.
I grabbed a 1250ml coke bottle ( leftover from Pizza and Scotch last night ), And drilled some holes in the bottom, filled it with my Mt Sylvia Diatomite and left the lid off
Weighed it at 530 Grams ( empty Bottle was 30g or so).
Soaked it in water for an hour or so went I went out, and then stood on a bench for 1 hr to drain
Just weighed it now and the total weight is 1075 g

From My test here seems that my Diatomite will hold it own weight in water ?

We will have to wait for Grant to do some different tests.

Ken

kcpoole wrote:No Worries grant
How much do you need? I was going to send a small bucket down
I have "Mt Sylvia" Diatomite not Maidenwell. The only difference I can see is the colour

Ken