I'm assuming you intend to grow in containers and as such for the medium in which I would grow bosai, the answer is zero. It depends on the particle size of the potting medium. 1/4" bark won't really lift water at all whereas pure clay will lift water quite high. You should ask this question in the bonsai forum though I imagine they will scold you and tell you to set up a proper irrigation system and use a fast draining medium.

Okay, I will try reposting my question in the bonsai forum, but anyway thank you for the answers!

But still, the saturation may not be as high for bonsai soil as for clay, but it would still manage to suck up at least some water to a certain height, right? In that way I think I still could used the construction I have planned to use, just that I need to find a soil mixture that pulls up just the right concentration of water, which is why I think this may still be the right forum to ask the question in.

So now my question is: How can I compose the soil to make it suck up just the right amount of water to about 1 feet above the water level in order to obtain a water saturation that trees thrive in? Is there any way to calculate approximately which mixture I should use or do I just have to try it out?

if you stand a pot in a tray of water it will draw that water in enough to keep the plant well watered, we have 3 foot high pile of dirt and when we dig in about 1 foot through dry soil the soil gets more moist as you dig.

len

Here is a link that might be useful: lens garden page

That depends on how much organic matter is in that soil. The mineral portion of the soil, the sand, silt, and clay, are not going to be much help in moving water upwards by capillary action, but organic matter will.

kimm - disagree completely. Fine textured soilswill move water upwards significantly via capillary rise. In fine textured clay soils capillary rise will move water upwards several feet, with 3-6 feet not being uncommon. In fact, depending upon the nature of the soil OM, it can inhibit capillary rise of water in soils.

Altai - since you will be growing bonsai in containers, your question is better posted in the container or bonsai forum. There are folks there who really know about constructing soils for those situations, more so than those who frequent these this forum.

A soils ability to move water upwards, called capillary rise, is a function of primarily soil texture and structure. It depends upon the nature of the porosity in the soil, both pore size and pore amount. Generally finer textured soils (high clay and silt levels vs. sand) will move water upwards to greater heights. Again, depending upon the nature of the mineral components texture and structure, organic matter can either impede or enhance capillary rise depending upon how the OM alters both the soils texture and structure, and now on the degree of hydrophobicity or hydrophilicty of the OM that is added. In general, adding OM to most soils will increase water penetration via gravitation and water retention, but it is often detrimental to capillary rise. Depending on the situation that can either be desirable or not.

A couple of issues with capillary rise are it can lead to anaerobic conditions in soils if the soil remains saturated for a prolonged period. On natural soils (i.e., not in containers) it can also move salts upwards from lower subsoil levels, and concentrate them in the root zone.

Where I live the native soils are heavy clay. Almost every night in dry periods I can witness the effect of capillary rise in our concrete paved streets. Perched water from several feet beneath the streets surface moves upwards via capillary rise and oozes and bubbles through small cracks in the pavement, even during drought periods.

unl, Whomever that is, says The water rises highest in the clay because it has the smallest pores. The clay soil exerts the greatest capillary action on the water. but it does not say how much. I don't know if the theoretical 32 foot limit we learned in high school general science classes applies to capillary action or not. I'm guessing it does not.

The 32 foot limit does hold even for capillary action. Capillary action basically just creates a pressure difference over the interface between the air and the water (due to surface tension), so while the air is at atmospheric pressure, the water pressure will be lower. Then the transportation of the water works basically in the same way a straw sucks up water and here the 32 foot limit still holds.

The finer the pores through which the water is sucked are, the greater the pressure difference will be; that's why clay absorbs water much better than sand which virtually can't suck up the water to any height at all. In a soil, the pore size isn't uniform, so a portion of the pores will be able to create the pressure difference required to suck up water to the height where they are, while a portion of the pores won't so they will contain air instead, so the soil will only be partially saturated with water. As the height increases, fewer of these pores are able to create the pressure difference required for that height, so the saturation will naturally decrease, continuously, as the height increases (and not abruptly at a certain height).

This post was edited by Altai on Sat, Jul 27, 13 at 16:44

albert - I believe the 32' limit you are thinking about is the maximum height that can be drawn by pump (vacuum), and that is limited by atmospheric pressure (32' of water) - the water is not actually sucked up, it is pushed up by the difference in pressure inside the tube/hose.

For capillary rise, the forces are surface tension of the water against the wall of the tube, the cohesive force that holds the water together, against gravity. The pressure difference isn't a factor for capillary rise. The limiting height is when the forces of capillary action is balanced by gravity. A smaller tube yields a greater height. It's typical in science classes to do a calculation for how far water can be drawn upward in a tree by capillary rise. Depending on what number is used for the diameter of a xylem tube, the result is usually about 20-30 feet. In soil, I have seen numbers around 30 feet for very fine clays; in coarse sands it is a few inches.

Clay/silt/sand types (parent materials), ratio of clay/silt/sand, pore sizes and their distribution, compaction, amount/size/type of organic matter and their degree of decay...general soil physical properties...these things matter when water wicking properties are being determined. External influences such as temperature also matter, too.

Some clay+silt combos are so fine and made of materials that easily bind fine organic matter that they are almost a roadblock to water...you'll find some of these in the NorthWest, Texas, and parts of SoCal for instance.

Some clays will greatly expand/heave/swell when water is introduced...soaking them up like a sponge and expanding volume rather than wicking through the soil profile.

Much like you would treat a material for building a structure...soil should be viewed as "engineered" for a purpose...whether it's a soil you're building from scratch or it's an existing soil you have to adapt methods in order to get it to do what you desire.

It's highly dependent upon what you're mixing up for a certain purpose or what you have to adapt to in order to get desired results.

This post was edited by nc-crn on Sat, Jul 27, 13 at 18:08