Victor Martinez wrote:

These are desert species that get neither rain nor fertilizer.


Eh, they get some rain - but not acre-feet of it in the space of two
months, I'm thinking. Fertilizer they do have, in the form dust and
soil that migrates on the wind, as well as animal droppings and such.

I do refresh the soil surface with fresh sand in late fall before I
bring the pot in for the winter, but I don't water from mid-November
until the pot goes back out in April so any nutrients in the fresh sand
pretty much stay in the fresh sand. The teaspoon of fish emulsion in a
gallon of water, most of which runs through, has to substitute for the
droppings