ACA. a N fertilizer additive, is now marketed by United Agri Products of Greeley, Colorado. ACA was developed by Amoco in the mid-1970s. Originally, they developed a soluble form of Zn to market in their anhydrous. The form of Zn was zinc acetate. They noted in some of their tests that at low rates of Zinc acetate they obtained yield increases under conditions where there was no indication from foliar Zn analysis that soil Zn was inadequate. Zinc acetate in strong ammonia solutions exists as 1 molecule of Zn with 2 molecules of acetate, and in the presence of adequate ammonia, 4 molecules of ammonia hold the zinc carboxylate so that it does not ionize. If the complex is diluted with water to the extent that the complex is not held together, a zinc hydroxide precipitate begins to form. Upon further dilution, Zn comes back into solution as the ion. I believe that using ACA in a manner which maintains the zinc acetate ammonia complex is essential for ACA activity.