Urea ammonium nitrate placement methods, row patterns, and irrigation effects on corn productivity in a humid subtropical region

Crop yields are adversely affected by nitrogen (N) losses in humid subtropical regions. This study was conducted to determine whether N dynamics could be manipulated through planting geometry and fertilizer placement. The effects of irrigation (irrigated and rainfed), row pattern (single- and twin-row), and N placement (surface dribble, one knife, two knives, and control) on corn (Zea mays L.) productivity and N use efficiency were investigated at Leland, Mississippi, on a Bosket very fine sandy loam. The total N rate was split into two equal halves of 128 kg N ha-1 at V2 and V6 growth stages. The effects of row pattern and N placement were consistent between irrigated and rainfed environments. There was no interaction between row pattern and N placement nor did row pattern affect corn productivity or N use efficiency parameters. In 2020, when less than 30 mm of rainfall occurred from the first N application through 2 weeks after the last N application, corn grain yield and agronomic N efficiency were not different among placement methods and averaged 11.1 Mg ha-1 and 20.3 kg grain kg-1 fertilizer N, respectively. However, in 2021, applying N with one knife increased corn grain yield by 7% to 14% compared to the two knives and surface dribble application methods; in that year, 235 mm of rainfall occurred from the first N application through 2 weeks after the last N application. Applying N with one knife appears to consistently improve crop productivity and N use efficiency parameters for both irrigated and rainfed environments. Weather (i.e., rainfall) influenced nitrogen (N) availability and corn productivity in the Mississippi Delta.Irrigation during reproductive growth stages increased yield by 9.3% compared to rainfed in 2021.Row pattern configurations had minimal effect on crop productivity and N dynamics.Corn yield in the surface dribble was 12.4% less compared to one-knife placement in 2021.