Are there any studies that show humic acid can reduce urea volatilization?

I did a small trial with dosi tubes and soil in pans with granular urea with humic acid both applied as a powder to the prills and in a liquid sprayed onto it. It was no better than plain urea, while the Agrotain treated urea had significantly less loss. I am planning on trying a similar trial with UAN mixed with humic when I can actually make a shovel go in the ground again because of frost.

I see now that there are some urea products that are formulated with humic right in the prill which would allow for much more humic acid to be present than an exterior coating.