Bihrmann's   CAUDICIFORMS   

 Water   Watering   Nutrition  pH   Light   Ventilation  Temp.   Soil   Pots   Pruning   Rest

The soil have several functions for our plants. It have to hold them in position, supply them with water and the nutrition's within it. At the same time, it have to let oxygen into the roots, and not harm the roots in any way.
Different plants thrive the best in different soils, but many can be grown in the same. Besides from the Nutrition and pH, the soil have to be able to hold sufficient Water through the needed period. At the same time, it have to drain enough to let fresh air get to the roots with oxygen, and takeaway carbon-oxide.
There is a huge difference in the soil you find in the wild, and what we are able to grow our plants in, in small Pots. In the wild, the plants roots covers a huge area under ground, compared to a pot, and that let the roots breath in a way more compact media. We need a way-more open compound, allowing water to drain fast to let the air to circle around.

A mixture with small medium capillary that hold the water till the plant absorbers it up, and larger capillary that drains and let air through. At the same time, it have to be able to maintain the right pH, and hold the nutrition. pH can be tricky, but a neutral media and the right watering water usually does it. Use sphagnum to lover the pH and limestone to raise it.
Unless you use fertilizer every time you water, you will need raw clay to bind the ions that makeup the nutrition. About 3-5% usually does it. 

If you are able to balance nutrition and pH, you should be able to use the same soil for many years in a row, just like in the nature. But it have to be structure stabile. If it holds too much fast decomposing organic material, it will soon end up choking the roots.

I have experienced how important organic / mineral soil is to some species, but never found a scientific explanation. Despite I fail to explain it, it have to be taken into consideration.
A lot of times, the origin give-up the soil, but sometimes, it is a bit tricky. Plants living on alkali limestone sound like they need a pH above 7, but they might grow in the small cracks, filled with acid organic material. Others might live in rain forest, but only as epiphytes, way up in the sun.

Which soil you chooses, will depend on the species, the environment, the Pots and how you are Watering - and what you can get your hands in.

 Water   Watering  Nutrition   pH   Light   Ventilation  Temp.   Soil   Pots   Pruning   Rest