Having previously identified poor N recovery as largely a denitrification problem, research began to investigate means of reducing N loss. In theory, denitrification Joss can be reduced by controlling the concentration of nitrate in the soil using nitrification inhibitors (which retard the oxidation of ammonium to nitrate), thus reducing the amount of nitrate available to the denitrification organisms. A recently-completed 3-year project evaluated the ability of nitrification inhibitors to improve N fertilizer recovery.