cheap greensand in VA?

Greetings folks,
I am trying to garden very frugally, and I like the slow release rock-based fertilizers such as rock phosphate, greensand, etc.
Espoma products are readily available, but they seem a little expensive to me. Are there fiscal shortcuts I could take to find long-term fertilizer sources of phosphate and potash?
Does anyone know of a cheap way to get rock phosphate, rock potash, greensand, granite dust, etc. in Virginia (I live in Harrisonburg).
Thanks!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.