Mix together the three ingredients and use in soil recipes instead of peat moss.
Store excess in an airtight container.
Notes
*I have a choice of either rice hulls or perlite as they have similar performance in the mix. This way you can choose the one that works for you. Rice hulls are a byproduct and can be found at home brewing supply shops very inexpensively. Perlite is more available as it is at every garden and home improvement store but it is a mined product.