As pollution control becomes more and more important, many industrial plants must collect particulate matter from their stacks which would otherwise be distributed over the nearby landscape. Some of these materials, with or without further treatment, are being sold or potentially could be sold as micronutrient fertilizers, especially zinc fertilizer. The efficacy of these materials in comparison to zinc sulfate (ZnSO₄), which is the most common zinc (Zn) fertilizer at the present time, was investigated.