However, these effects are temporary. Including a nitrification inhibitor with anhydrous ammonia applications can lengthen the period of bacterial inhibition. Research indicates that nitrification inhibitors, such as dicyandiamide (DCD) and N-serve, can protect fall nitrogen against loss and increase the amount of nitrogen present in ammonium form the following spring.
"As with most practices, using a nitrification inhibitor might not pay every year," Fernández says. "If the following spring is dry and cool, the inhibitor might not be as effective at enhancing ammonium recovery. However, this practice will, overall, offer the best chance to protect your nitrogen investment and the environment."
Ammonium sulfate is an excellent source for no-till fields where broadcast applications are preferred. It is always best to apply it before soils freeze so the fertilizer can dissolve and rain can incorporate it into the soil. In fields with minimal slope (less than 5 percent) with low run-off potential, ammonium sulfate can be applied on frozen ground because volatilization losses are unlikely.
"Ammonium sulfate is more acidifying than other nitrogen sources, so make sure to keep an eye on soil pH," Fernández advises. "As a general rule, 5 pounds of lime is needed to neutralize 1 pound of nitrogen from ammonium sulfate compared to 2 pounds of lime per pound of nitrogen from anhydrous ammonia."
Organic fertilizers derived from animals (manure, poultry litter) are good fertilizer sources that can be used in the fall. These products supply nitrogen as well as phosphorus, potassium, and other crop nutrients, and are often less expensive than inorganic fertilizers.