Originally Posted by paradoxlost
My source is USGS. I'm on my phone but I have the document at my house on my laptop.
I think you must have read it wrong. You'll be hard pressed to find any knowledgeable people that wouldn't say you'd be risking toxicity above 5 ppm. The University of Wisconsin, Oxford, Oregon State Ag Dept, Agricultural Canadian Research Station, Graime Said, etc. all say 5 ppm is about the healthy limit in soil. Spectrum Analytics says 1 ppm is sufficient for most crops and most of the rest say around 0.5-2ppm is sufficient for most crops.
And just FYI, you could use ammonium molybdate or molybdenum trioxide also, but I don't know how cheap or easy to find those are. Sodium molybdate is cheap and easy to find.