APPLICATION PLACEMENT AND TIMING OF NITROGEN SOLUTION FOR NO-TILL CORN

Fertilizing no-till corn (Zea mays L.) with urea-based N sources requi res managing for N losses such as immobilization and NH3 volatilizatio n. In this study the interactive effects of fertilizer N application t ime and placement method were evaluated by applying urea ammonium nitr ate (UAN) solution to no-till corn. Eight site-years of data were coll ected from sites in central, northeast, and northwest Missouri on Ochr aqualf, Albaqualf, and Udifluvent soils, respectively. Experimental de sign was a complete factorial of N application time (preplant and side dress), placement method (knife, dribble and broadcast) and rate (67, 135, and 202 kg N ha-1). Knife injected N increased yields relative to broadcast and dribbled N in five of eight site-years. Yields from kni fe injected N ranged from 4 to 20% more than dribble and 5 to 40% more than broadcast. Ear-leaf N concentration and grain N uptake were incr eased from knife injected N in six of the eight site-years. Dribbled a nd broadcast UAN performed similarly in most site-years for grain yiel d, ear-leaf N and grain N uptake. Except for two site-years in which s idedress resulted in lower grain yields, application time had no effec t on grain yield. No interaction of application time and placement met hod was apparent, as knife injection was superior to broadcast and dri bble at both application times. This suggests that N losses associated with surface application of urea-based N sources were similar for pre plant and sidedress application times.