Nitrogen‐15 evaluation of fertilizer placement at planting for corn production.

Numerous studies have been reported to ascertain the benefits of starter fertilization for corn (Zea mays L.) production, but most rely on data collected by measuring early growth or grain yield at harvest. As a more conclusive evaluation, five field trials were conducted using 15N‐labeled urea‐ammonium nitrate (UAN) solution (90 kg N ha−1) to compare single and dual subsurface band placement, as well as surface dribble and broadcasting with incorporation. Significant differences in dry matter production and total N uptake occurred between fertilized and unfertilized treatments, but not among the different placements studied. In contrast, fertilizer 15N uptake efficiency (F15NUE) tended to be greater for either type of subsurface banding than for the dribble treatment, demonstrating the added sensitivity that can be achieved through isotopic measurements. More importantly, band placement consistently outperformed broadcasting, according to estimates of F15NUE for total aboveground biomass that ranged from 11% to 46% when UAN was banded and from 7% to 34% for broadcast applications. Core Ideas: A field study was conducted using 15N‐labeled urea‐ammonium nitrate to evaluate fertilizer placement at planting for corn production.Fertilizer 15N uptake efficiency ranged from 5% to 34% for grain and from 7% to 46% for total aboveground biomass.Banded placement was consistently more efficient than broadcast fertilization. [ABSTRACT FROM AUTHOR]