Assessing pre-plant nitrogen sources and waterlogging on corn growth and yield

Flooding and waterlogging from strong storms can negatively affect corn (Zea mays L.) growth and yield. Ensuring adequate nitrogen (N) supply after waterlogging is key to optimizing corn yield, though limited evaluations of enhanced efficiency fertilizers have been conducted in conjunction with waterlogging conditions. The objective was to quantify how different pre-plant incorporated N sources and post-emergence waterlogging affect corn N uptake, yield, and efficiency of applied N. A split-plot randomized complete block design was conducted in two locations from 2021–2023. Waterlogging regimes (0 or 4 days) were implemented by applying water at the V4–V6 growth stage. Pre-plant incorporated N source was the subplot factor consisting of a non-fertilized control or 200 lbs N acre⁻¹ applied as urea (U; 46–0–0) or urea-ammonium nitrate (UAN; 28–0–0) alone or combined with either nitrapyrin or N-(n-butyl) thiophosphoric triamide (NBPT), and polymer-coated urea (PCU, 44–0–0). The optimum ear leaf N concentration at R1 (2.75%–3.50%) was only achieved with U and PCU when waterlogging occurred. Waterlogging reduced grain yield by 9% to 25%, while N source (across waterlogging treatments) increased grain yield over the non-fertilized treatment by 14% to 45% or 236% to 343%, depending on location. Grain yield was optimized with U, PCU, and U with nitrapyrin regardless of waterlogging condition. Dry fertilizer sources also resulted in higher partial factor productivity compared to UAN treatments. These results suggest that dry N sources of U, PCU, or U with nitrapyrin should be considered in regions prone to waterlogging to optimize corn grain yield.