Efficacy of UAN Placement Distance On 15N Uptake and Recovery and Corn Grain Yield.

Title:   Efficacy of UAN Placement Distance on ¹⁵N Uptake and Recovery and Corn   Grain Yield

Authors: Jon M. Carson

Abstract:  Improving nitrogen (N) management in corn production has been the subject of considerable research in the past. Current recommendations suggest knifing fertilizer N in the center of the furrow to help prevent root pruning when N is split applied. However, such placement could potentially result in increased N loss, leading to reduced NUE and grain yield. The objective of this research was to evaluate crop N uptake and corn grain yield as influenced by urea-ammonium nitrate (UAN) fertilizer placement distance from the corn row. Treatments included ¹⁵N labeled fertilizer applied at 15, 30, and 45 cm distances from the corn row using both surface and subsurface banded application. Fertilizer N was split-applied at 180 kg ha^-1, with 50% applied at V3/V4 followed by 50% applied at the V5/V6 growth stage. Data collection included ear leaf samples at vegetative tasseling, and whole plant and grain samples at physiological maturity for determination of ¹⁵N recovery, total N uptake, and grain yield. Results from 2011 and 2012 show increased NUE, ¹⁵N recovery, and grain yield as N fertilizer is placed in closer proximity to the planted row. In addition, results show that the average total ¹⁵N recovery increased 22% and grain yield increased 14% in both growing seasons as N fertilizer placement decreased from 45 to 15 cm from the row. Results from this study indicated an overall combination of fertilizer N placement distance at 15 cm and subsurface banding resulted in greater fertilizer ¹⁵N recovery, total N uptake, and corn grain yield both years. Data provided definitive documentation to further optimize in field placement of N fertilizer and maximize profitability.