Core Ideas Excessive soil moisture resulting from extreme precipitation events during early spring can often cause decreases in corn grain yields in the midwestern United States. Each day of waterlogging resulted in an average corn grain yield loss of 0.42 Mg ha−1 and 0.72 Mg ha−1 in 2013 and 2014, respectively. Pre‐plant N fertilizer applications of non‐coated urea; polymer coated urea, and non‐coated urea+nitrification inhibitor resulted in 19% higher yields compared to the non‐treated control in 2014. Effects of rescue N fertilizer were seen on soybean yields in the succeeding year after corn, while rescue N affected corn yields only in 2014. Climatic conditions including rainfall and air temperature had a significant role in crop response to waterlogging and N fertilizer treatments. In the midwestern United States, excessive soil moisture resulting from extreme precipitation events during early spring can often cause decreases in corn (Zea mays L.) grain yields and escalate N loss. A field trial was conducted from 2013 to 2015 in Northeast Missouri to determine the effects of soil waterlogging duration, pre‐plant N and rescue N fertilizer applications on corn and succeeding soybean [Glycine max (L.) Merr] production. Plots were either non‐flooded or flooded for durations of 1, 3, or 7 d when corn was at V6 growth stage. Pre‐plant N fertilizer treatments included non‐treated control (CO), urea (NCU), urea plus nitrapyrin (NCU+NI), and polymer coated urea (PCU) applied at 168 kg N ha−1. A rescue N fertilizer application of 0 or 84 kg N ha−1 of urea plus N‐(n‐butyl) thiophosphoric triamide (NBPT) (NCU+UI) was applied at V10 growth stage. Each day of waterlogging resulted in an average corn grain yield loss of 0.42 and 0.72 Mg ha−1 in 2013 and 2014, respectively. Pre‐plant N fertilizer applications of NCU, PCU, and NCU+NI resulted in 19% higher yields compared to CO in 2014. Effects of rescue N fertilizer were seen on soybean yields in the succeeding year after corn, while rescue N positively affected corn yields only in 2014. These results indicated that rescue N fertilizer applications are not effective if drought conditions occur after its application in corn. Climatic conditions including rainfall and air temperature had a significant role in crop response to waterlogging and N fertilizer treatments.

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Poorly-drained claypan soils in the Midwestern United States experience periods of short-term soil saturation shortly after pre-plant N fertilization, which may result in relatively large amounts of soil surface N 2 O emissions. Slowing the release or conversion of N fertilizer to soil NO 3 early in the growing season through the use of enhanced efficiency fertilizers (EEF) could be an effective strategy for reducing soil N 2 O emissions and gaseous N loss during a period of relatively low plant N demand. The objective of this study was to determine the effects of short-term soil waterlogging and pre-plant applications of conventional and EEF on soil inorganic N and N 2 O emissions during and up to four days following a waterlogging event during the dry down period. A two-year field study planted to corn (Zea mays L.) was initiated in 2012 on a poorly-drained claypan soil in Northeast Missouri. Waterlogging treatments were initiated at the V6 corn stage of phenological development. Main plots consisted of no waterlogging or water ponded 7 to 13 cm above the soil surface for three days, and sub-plot N fertilizer treatments [non-treated control (CO), or preplant broadcast applications of 168 kg N ha -1 of urea (NCU), urea plus nitrapyrin nitrification inhibitor (NCU+NI), and polymer coated urea (PCU)]. In 2012, greater cumulative soil N 2 O-N emissions of 2.8 kg N 2 O-N ha -1 were observed with PCU in comparison to NCU over the entire seven day sampling period. A significant portion of cumulative soil N 2 O emissions were associated with the four day soil drying phase in 2012, where PCU and NCU+NI had greater emissions (1.9 and 1.2 kg N 2 O-N ha -1 ) compared to NCU. The proportion of N fertilizer lost as N 2 O-N averaged over all pre-plant N treatments during the 2012 and 2013 sampling periods in the non-waterlogged soils were 0.04% and 0.03%, and 1.1% and 2.6% in the waterlogged soils, respectively. These results suggest that a large proportion of the cumulative soil surface N 2 O emissions typically observed in these poorly-drained soils over a growing season may occur during and shortly after soil waterlogging events.

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Identification of corn hybrids that can withstand wet soil conditions is one approach to prevent crop production losses from abiotic stress caused by excessive soil moisture during early spring season in the midwestern United States. A greenhouse pot experiment was conducted in 2013 to screen and identify corn hybrids tolerant or susceptible to soil waterlogging at the V2 growth stage. The main plots included waterlogging durations: no waterlogging; 14-day waterlogging and then allowing recovery from waterlogging stress for 7 days; and 21-day waterlogging. Subplots included eight commercial corn hybrids. The shoot and root biomass, plant height, stomatal conductance, and chlorophyll meter readings were decreased due to waterlogging for 14 days and 21 days. Hybrid #2 appeared to be more tolerant to waterlogging as evidenced by greater growth and higher stomatal conductance and chlorophyll meter readings on newer leaves under waterlogged conditions. Hybrid #5 and Hybrid #8 were more susceptible to waterlogging than other hybrids. Large variability occurred among corn hybrids in response to soil waterlogging durations. Beneficial effects of improved soil conditions after excess water removal from 14-day waterlogged pots were not seen in this experiment, probably due to the short recovery time period between the excess water removal and experiment termination.

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