Fate of Subsurface‐Banded and Broadcast Nitrogen Applied to Tall Fescue

The purpose of this study was to determine why N uptake and forage production by tall fescue (Festuca arundinaceaSchreb.) in southeastern Kansas are greater from subsurface‐banded (knifed) than from broadcast N applications. The fate of urea N fertilizer applied to tall fescue either broadcast or banded in 1982 was determined using a urea ammonium nitrate (UAN) solution containing 15N tagged urea and measuring various components of the N balance. Plant uptake of residual urea N was measured during 1983. In 1982, 62% of the banded urea N was recovered in harvested forage, whereas only 40% was recovered in the broadcast treatment. Tagged N remaining in the soil as residual N at the end of 1982 amounted to 40 and 45% for broadcast and band treatments, respectively. Most of this residual N was not available to plants in 1983 since only 1.4 kg fertilizer N ha−1(5–6% of the residual N) was recovered in the forage. About 1% of the banded N was unaccounted for, indicating that gaseous losses (denitrification and ammonia volatilization) were about 1% of the applied urea N, whereas 23% of the broadcast urea N was unaccounted for, indicating probable significant gaseous losses. These results suggest that the improved efficiency of knifed N over broadcast N observed in southeastern Kansas may be due to reduced gaseous N losses.