Impact of split nitrogen applications on nitrate leaching and maize yield in irrigated loamy sand soils of Northeast Nebraska

Little information is available on optimizing the number of nitrogen (N) splits based on nitrate (NO₃-N) leaching and maize yield in sandy soils. To address this gap, we evaluated the impact of multiple N splits (2-, 3-, 4-, and 5-N splits) on NO₃-N leaching and maize (Zea mays L.) grain yield in irrigated loamy sand soil at a producer site in the Bazile Groundwater Management Area of Northeast Nebraska. Porous suction cup lysimeters were installed at a depth of 120 cm to collect pore water samples from 23 leaching events in 2021, a dry year. Increasing the number of N-splits did not affect the pore-water NO₃-N concentration; however, it was 169%, 152%, 150%, and 129% higher in 2-, 3-, 4-, and 5-N split treatments compared to control, that is, without N application. Though the 2-, 3-, 4-, and 5-N splits had 110%, 71%, 120%, and 91% higher area-based NO₃-N leaching than the control, less deep percolation and more evapotranspiration in control led to no significant differences in area-based NO₃-N leaching among all treatments. All N-splits resulted in higher maize yield, nitrogen use efficiency, plant N uptake, harvest index, and aboveground biomass than control; however, the number of N-splits did not affect these parameters. The inclusion of environmental cost reduced the return to nitrogen by 92–143 $ ha⁻¹ across all N-split treatments but did not significantly affect the differences among the splits. Overall, the results indicate that increasing the number of N-splits does not provide agronomic, economic, and environmental benefits in irrigated maize fields during a dry year.