A substrate suggestion for Dyckias

Pine bark. This is used as bulk material. The bark must be decomposed
and absolutely free from any pine resin. This material is at plenty and low cost
in areas where pine plantation is largely made for paper making.
Use materials that are at plenty in your area, easily obtainable and at a low cost.

Chicken bed.
Every time the aviary send the chicken to the slaughterhouse the chicken bed is removed and renewed. It is basically old sawdust, chicken droppings and feathers. It is extremely rich in nitrogen. Plant use this for growing and getting strong and green. Use it parsimoniously and may be used constantly sprinkled on the substrate. Dyckias love it.
It stinks! To some it is one lovely farm perfume, others disgust.

Burned rice husk. This brings minerals and micro nutrients to the substrate.
Carbonized rice shells is largely used in Tropics. It is cheap and easily obtainable
in this regions.

The final substrate looks.
It must be light and aerated all the time.
Substrate recipes are as numerous as the sand grains in a tropical beach.
Dyckias show you if they are happy or not with your treatment.
Try to be wise and use as much information as you can.
Do not use soil! Any kind of it, stay away from garden soils and so on.
One substrate may do fine here and poorly in your area.
Light, temperature and humidity are the three main factors
to determine what recipe to use.
Talk to locals, see their results and try to do it better yet.
You mind will make you to know if a substrate is working and doing good or not.
This sensation is natural to all of us. We sense what is healthy and safe in therms of plants, herbs and vegetables.