Hl. Lees et al., Increased plant nitrogen loss with increasing nitrogen applied in winter wheat observed with (15)nitrogen, J PLANT NUT, 23(2), 2000, pp. 219-230
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 re
covery in winter wheat when produced for forage and grain, and to quantify
potential plant N losses from flowering to maturity in winter wheat. Two lo
ng-term (>25 years) winter wheat (Triticum aestivum L.)N sate fertility exp
eriments (Experiment 222 and Experiment 502) were selected to evaluate N-15
fertilizer recovery. Percent N-15 recovery was determined from all micropl
ots in plant tissue at flowering, in the grain, and straw at harvest and in
the soil. Fertilizer N ((NH4)-N-15 (NO3)-N-15) was applied at rates of 0,
45, 90, and 135 kg N ha(-1) in Experiment 222, and 0, 22, 45, 67, 90, and 1
12 kg N ha(-1) in Experiment 502. The ratio of NO3- to NH4 (+) in wheat for
age at flowering was positively correlated with estimated plant N loss. Est
imated 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
.