Equiv fluid pressure of bulk fertilizer

[PostFrameSE]

I'm supposed to be putting some preliminary numbers together to retain some bulk fertilizer. Is there a conservative way to estimate the fluid pressure that would be exerted on the wall due to various types of bulk fertilizer? Is salt storage retaining wall design much different?

Thanks.

 

[STVU]

Get the unit weight of the fertilizer and multiply it by 0.5 to get approximate equivalent fluid pressure. Similar approach for salt storage.