LAUSR

2059 Spring pre-plant N applications are considered a bestmanagement practice in conventionally tilled, poorly drained, mediumto fine-textured soils throughout the northern Corn Belt (Vetsch and Randall, 2004). Corn (Zea mays L.) yield potential is affected by a multitude of agronomic practices (e.g., fertility management), cultivars, and the environment (Evans and Fischer, 1999). Recent data project more frequent heat waves (i.e., >5°C above climatic normal) and increasing air temperatures (1.5–2.0°C) over the next 30 yr that may affect spring frost dates in the northern hemisphere and increase precipitation intensity during winter and spring months (>50.8 mm in 48 h) (Hayhoe et al., 2007; Karl et al., 2009). Warmer spring temperatures may shift corn planting dates earlier than currently recommended (Lauer et al., 1999). Weather variability may increase risk of early applied N losses (i.e., volatilization, leaching, and denitrification) and require reexamination of N management strategies (Scharf et al., 2002). Optimal soil fertility management includes adjusting strategies to account for the proper placement, time, source, and rate (e.g., 4R) of N adapted to siteor region-specific environments (Roberts, 2007). Rapid corn N uptake does not occur until the V10 growth stage (Bender et al., 2013). Delayed sidedress (SD) N applications (e.g., after V10) may help mitigate the time lapse between N application and uptake but further research is needed to refine current grower practices. Pre-plant incorporation (PPI) is a one-pass N strategy where 100% of the N inputs are applied up to planting time and incorporated. A large percentage of Michigan corn land area is grown on calcareous soils with a soil pH > 7.2, which can increase NH3 volatilization losses, increase N immobilization, and reduce the efficiency of surface-applied urea containing N fertilizers (Havlin et al., 2014). In Michigan studies, blending polymer-coated urea (PCU) with urea (75:25, PCU/urea blend ratio) has improved efficiency of urea containing fertilizers. For example, when April and May precipitation were above average, PCU/urea broadcast 2 to 4 wk before planting and incorporated improved corn yield up to 1.38 Mg ha–1 relative to 100% urea PPI (Franzen, 2017). In the same studies a PCU/ urea blend extended N activity in dry soils, which increased corn grain yield 1.07 Mg ha–1 relative to a V4 to V6 surface Pre-Plant and In-Season Nitrogen Combinations for the Northern Corn Belt