Other additives do little if anything to preserve hay. Some hay preservative products dilute the proponic acid and require greater product use rates. Rates of propionic acid required to preserve hay vary with the moisture content of the hay. Note that rates are for pounds of propionate not product. Acetic acid is about half as effective as a preservative and therefore requires twice as much product for equal preservation.
Anhydrous ammonia is an effective preservative for grasses.
It can be injected into bales or released into a stack of bales covered and tightly sealed with plastic. Anhydrous ammonia should not be used as a preservative on alfalfa because the additional nitrogen is of little benefit to animals and toxic chemicals can form in the hay. Currently, evidence is not sufficient to indicate that microbial hay preservatives are effective in preserving hay.