Placement and Timing of Nitrogen Fertilizers for Conventional and Conservation TillageCorn Production

Increased use of reduced tillage to meet soil and water conservation goals in corn (Zeamays L.) production emphasizes the need to manage fertilizer N efficiently in these systems. A 3‐yrstudy to evaluate N fertilizer source, placement, and timing options in four tillage systems wasconducted on a Piano silt loam (fine‐silty, mixed, mesic Typic Argiudoll) and a Manawa silty clayloam (fine, mixed, mesic Aquollic Hapludalf) using a split‐split plot treatment arrangement withfour replicates. Main plot treatments were moldboard plow (MP), chisel plow (CP), ridge‐till (RT),and no‐till (NT). Sub‐plot treatments were rates of 90 and 180 lb N/acre, and sub‐sub‐plottreatments were seven N application methods (NAM). Grain yields in MP were higher than in NT on thePiano soil. Yields were significantly higher at the 180 lb N/acre rate than at 90 lb N/acre, anddiffered with NAM. Effects due to NAM were usually small (8–10 bu/acre), and similar, near‐maximumyields were obtained with preemergence applied anhydrous NH3 with or without nitrapyrin[2‐chloro‐6‐(trichloromethyl) pyridine], or N‐Serve (N‐S), surface broadcast urea‐NH4NO3 solution (UAN), injected UAN with N‐S, and with sidedress injected UAN without N‐S. Resultsshow that the NAM evaluated usually can be used across a range of tillage systems without majoryield effects. Yields without added N were lower in NT than MP, suggesting lower soil N availabilityin NT. Ear leaf N concentration measurements did not always reflect small differences in yieldcaused by some N management practices.