Consequences of Shallow NH3 Placement and Timing On N Use Efficiencies in Corn Production.

Corn (Zea mays L.) production relies heavily on nitrogen (N) fertilizer. The recently introduced JD2510H shallow anhydrous ammonia applicator provides opportunity to farmers to side-dress fertilizer in later growth stages. Field studies were conducted between 2010 and 2012 near West Lafayette, IN to compare the effect of different timing and horizontal placements of anhydrous ammonia (AA) application (pre-plant 6” offset from corn rows versus mid-row side-dress application at the V6-7 growth stage) on N use efficiencies at multiple N rates (ranging from 0 to 200 kg ha^-1). Higher combine harvested yields were measured following side-dress application, especially when N was not limited. Total aboveground biomass and N uptake of corn at physiological maturity were not influenced by the application timing, but increased with applied N rates.

N recovery efficiency (NRE), N internal efficiency (NIE) and N use efficiency (NUE) were calculated from biomass samples. These N efficiency indices decreased with increased N rate, but were not affected by AA timing. Ear leaf N concentrations at silking time were strongly correlated with total plant N uptake at physiological maturity and final combine harvest grain yield.