Thanks for all the information, guys! I liked the idea of cutting the bottom out of the pots so they function like raised beds, I'm going to try this! I live in southern Brazil. I planted Southern Highbush and some rabbiteyes. The SHB are growing well, but I think the rabbiteyes won't do well in my climate because our winter is too warm for them. Something that I have noticed is that the rabbiteyes that I left in the shade have flowered, but the ones that stayed in full sun during the winter did not flower at all, their buds didn't open, I believe they didn't get enough chill hours... So I learned that the amount of chill hours can vary a lot depending on where you place the pot in the yard. So I guess what I will have to do with the rabbiteyes every year is leave them in the shade during all winter, and then move them to a sunny place during spring, summer and fall. This post was edited by julia.scheidt on Sun, Sep 7, 14 at 20:58

Soil porosity values are well documented and can even be calculated from the various particle sizes in the soil. Published values (percent air space within the soil) range from about 40%-60%, usually very close to 50%. This holds all the way to pure sand and even larger solid materials, as shown by your gravel result. Your value of 30% is anomolously low, perhaps because there was a small amount of water already present, perhaps experimental error (since the water capacity was measured at 35%, physically impossible to be more than the porosity). Published values for the water holding capacity are generally about 10% lower than the total porosity for mineral soils. The value of 35% for your soil is actually at the low end (again there may have been 5%-10% moisture already in the soil), with values up to 50% for heavy soils being quite common. Sand, and fine gravels, are much lower, around the 25% value you show for gravel. They don't describe peat as "fluffy" for nothing ;) One of the problems with peat is the very large difference between the amount of water retained from a dynamic watering, and the maximum amount of water which can be soaked up, for example from standing in a saucer. This is what you referred to as wettability in another thread. Although peat retains air from a simple watering, it can become almost fully saturated from being allowed t soak up water. You can measure this by a third experiment where the cup is allowed to stand in water for a few hours. I believe that the same thing applies to the calcined clays like Turface although I can't find any published experiments on this. It is certainly a valuable property in a soil because, as we discussed on the other thread, it will often reduce or eliminate a perched water table after a pot has been watered from above. Perlite does not show this property because it is a closed cell granule. The air pockets within each particle are not open to the exterior in any way. This shows in the very low saturation number you found and is also apparent in the willingness to float. Volcanic rocks are very variable, some closed cell, some open, and the cell size and base density of the rock varies. Yours shows the properties of a closed cell rock, or perhaps it is simply a very coarse rock with large internal cells. Of course it still remains to discuss what ideal values of these properties might be in a succulent container soil. Total porosity is often mentioned and it is claimed that it should be 60%-70%, certainly never below 50%. I feel that this isn't the most important number, rather that the air space remaining after you water is critical for succulents, as indicated by the lower saturation numbers in your table. I suspect that rather dense soils are valuable for many succulents, certainly Lithops and some cacti seem to prefer a soil which would have low total porosity. Others prefer a much higher porosity, I would suggest that fleshy rooted species like Ectotropis, Haworthias, and some cacti, prefer a especially open soil (although possibly require regular watering in such a soil). Lastly I still claim that the wettability, or lack of it, is important, possibly more important than any of the measurements here. In your experiment where tipping a pot forces extra water to drain, when tipping the pot a few minutes later does not force extra water to drain the perched water table has been eliminated and this is a good thing. There are other ways to quickly reduce or eliminate perched water tables: porous clay pots; only watering in dry sunny weather; and only watering plants which are thirsty. On the other hand, some growers habitually water from below, I don't know whether this overrides any wettability issues to force a perched water table or actually reduces the amount of water retained within the soil because of limited capillary action or limited time standing in the water. Presumably all these things are possible and each grower has adapted a method which suits their own soil mixes and plants. My experience is that bottom watering is a way to put extra water into the soil and I only use occasionally for plants which are in peak growth or subject to very drying conditions (my soil and pots are chosen for safety in a cool humid climate and dry exceptionally quickly by in rare hot low humidity conditions).

No, i just want a few sections of the terrarium to be able to have mushrooms pop up, or continually pop up, depending on the temp or humidity, I plan on this being the source of oxygen for the plants. Im not sure how much they produce, but im sure it will help more than not having them, i plan on getting a strain that is very small, and can form dense clusters, therefore giving more conversion power from co2 to oxygen. I think i may try out a solid bark mix for about a week or some with a single plant of what i plan on putting in there while i let the rest of what im putting in grow, or germinate. MY MAIN CONCERN is still what kind of substrate to use for a mushroom and plant terrarium.

Local conditions and locally sourced/available materials probably drives what most people use. I use a garden soil modified with pine bark, perlite, and small lava rock. One could use any of the materials you have listed although I would recommend a very coarse sand if any.