Increased plant nitrogen loss with increasing nitrogen applied in winter wheat observed with ¹⁵nitrogen

Abstract

Nitrogen (N) fertilizer is generally the most costly input for winter wheat (Triticum aestivum L.) production. Therefore, it was important to maximize fertilizer use efficiency and minimize N losses to the environment. One of the mechanisms responsible for decreased N use efficiency (NUE) was plant N loss. The objectives of this experiment were to determine fertilizer N recovery in winter wheat when produced for forage and grain, and to quantify potential plant N losses from flowering to maturity in winter wheat. Two long‐term (>25 years) winter wheat (Triticum aestivum L.) N rate fertility experiments (Experiment 222 and Experiment 502) were selected to evaluate ¹⁵N fertilizer recovery. Percent ¹⁵N recovery was determined from all microplots in plant tissue at flowering, in the grain, and straw at harvest and in the soil. Fertilizer N(¹⁵NH₄ ¹⁵NO₃) was applied atratesof 0, 45, 90, and 135kg N ha^‐1 in Experiment 222, and 0, 22, 45, 67, 90, and 112 kg N ha^‐1 in Experiment 502. The ratio ofNO₃ ^‐to NH₄ ⁺ in wheat forage at flowering was positively correlated with estimated plant N loss. Estimated plant N loss (total N uptake in wheat at flowering minus N uptake in the grain and straw at maturity) ranged from a net gain of 12 kg N ha^‐1 to a loss of 42 kg N ha^‐1, and losses increased with increasing N applied.

Notes

Corresponding author (e‐mail address: [email protected]).