Effects of Early Season Saturation on Nitrogen Fertility in Corn.

Nitrogen is often the most limiting nutrient in crop production systems.  Management practices have the potential to increase the efficiency of N applications; however, environmental conditions can negate the impact of these management practices.   In the Mid-South, one of these environmental conditions is early season saturation.  While it is understood that these conditions can be detrimental for plant growth, little is known regarding the potential yield limitations and challenges with N management.  Therefore, a trial was established in St. Joseph and Winnsboro, Louisiana in 2015 to evaluate the effects of early season saturation on N management in corn.  Nitrogen was applied at a rate of 224 kg ha^-1 and 336 kg ha^-1.  After N was applied, saturation treatments were initiated at the V2/V3 growth stage.  The saturation was held for 24-hours and then allowed to drain naturally; however, no plots had greater than 72 hours of standing water.  Soil samples to the depth of 1 meter were collected from the 336 kg ha^-1 immediately following N applications, as well as a successive sample was taken immediately following the saturation events.  At maturity, the middle two rows of a four-row plot were harvested to obtain grain yields.  Early season saturation resulted in a significant decrease in corn grain yields (by 18 and 15% of unsaturated yields for 224 and 336 kg ha^-1, respectively).  Additionally, saturated conditions significantly influenced soil N levels.  Overall, the implementation of saturated conditions decreased soil N concentrations to less than 10% of the pre-saturation concentrations.  This trial indicated that challenges exist for both crop management and N management in corn production systems following saturation events.    Therefore, systems in the Mid-South should focus on management practices which alleviate early season N losses as well as account for the potential decreased crop productivity.