Does Fertilizer Go Bad (& a couple other ?s)

[Ray]

The fact is that fertilizer dispensing should be done by mass, as it’s the mass of nutrients that’s important to plants, not the amount of dilution. Measuring powders by volume is a guesstimate at best, because the bulk density (mass per volume) varies.

One way around that is to make a liquid concentrate from a known weight of powder.

Or if you just want to stick with powders, here’s a calculator to help with units, both mass and volume estimates.