ok folks i will try some dolomite in my next mix!.
i forgot to tell you for micronutrients, such as magnesium, i use a spoonfull of diatomaceus earth every 8 litres.
i dont know if you call it river undertow i just kind of translate it from spanish "resaca de río" (i think the real word is "river waste"?) which is not taken from Andes but from Entre rios which is a province (state) in my country.
The river undertow is produced by the accumulation of vegetal residues under anaerobic conditions composting for a very long time. Like compost it has the same ammount of composted organic matter so it brings a lot of nutrients and also is very light it improves humidty conditions and the looseness, and a very large etccc (micorrizae for example).
the airation i get it with the mix of peats and the river undertow
we used vermiculite a lot in our country on war times or economical situations to cheapen out the soil mix. like coco coir, perlite, vermiculite, or expanded clay pebbles it dont bring any nutriens and its a waste of a big porcentge in the mix.
I only have information in spanish, but ive found an article on mandala´s web which is very easy to read:
an example of quality potting soil - the texture is fluffy & soft, made from fine-grade sphagnum peat, the white specks are traces of perlite. Notice how little perlite professional potting soil contains (1% of total volume)! One of the most common mistakes growers make is to ruin their soil mix with high amounts of perlite.
coco coir and perlite only adds to the lack of available nutrients in a container.
It is best not to add any additional materials to your potting soil. Horticultural grade potting soil is perfectly mixed for the best air-water ratio. Adding more non-nutritive substances depletes the water retention capacity of the soil, it unnecessarily "stretches" the soil and reduces the total amount of nutrients available to the plant, and it creates dry pockets in the container.
Adding a large amount of perlite/vermiculite (some growers add as much as 25%!) is a completely outdated practice from 30-40 years ago when there was only a very small selection of horticultural potting soil available for non-commercial gardeners. It is one of the unfortunate harmful practices in cannabis cultivation that many still cling to although they do not understand the reason or consequences.
Especially harmful is to fill the bottom of the container with coarse materials such as expanded clay pebbles. This is where most roots grow down looking for water and nutrients! If they reach a dry and sterile layer of substrate the delicate root hairs shrivel, valuable space is lost where the plant requires rich soil that stores moisture and minerals.
If you are planting outdoor and your soil is too compact a modest addition of perlite/vermiculite or sand helps to increase drainage. Humus, such as from compost, is the best additive because it also provides many microorganisms and nutrients to the soil mix.