Jarrod O. Miller, Extension Agronomist, jarrod@udel.edu
Heavy rains and ponding can leave corn fields waterlogged, reducing crop growth and causing a loss of nitrogen (N). A recent study examined how different types of pre-plant N sources will support corn growth under waterlogged conditions (Open access: https://doi.org/10.1002/cft2.70071)
In the study, corn was flooded for four days at the V4–V6 growth stage, and five N sources were compared at a rate of 200 lbs N per acre: urea, urea-ammonium nitrate (UAN), urea with nitrapyrin, urea with NBPT, and polymer-coated urea (PCU). Nitrapyrin and NBPT are additives that help nitrogen fertilizers work more efficiently in the soil, while polymer-coated urea (PCU) releases nitrogen slowly over time to match crop needs. All treatments were compared to a non-fertilized control.
Results showed that waterlogging reduced corn yield by 9% to 25%. For example, a potential 250 bushel corn crop could lose up to 63 bushels of yield with waterlogging. The most consistent yields were achieved with urea, PCU, and urea + nitrapyrin, whether or not waterlogging occurred. Dry fertilizer sources also showed higher nitrogen use efficiency compared to UAN.
The takeaway for farmers is that in regions or fields prone to flooding, dry N sources such as urea, polymer-coated urea, or urea with nitrapyrin should be considered over UAN to help maintain yield and improve efficiency.