Abstract

The study was conducted in Eastern Ethiopia, namely Meta and Tullo districts, during the 2015 cropping season to determine the effect of N fertilizer levels on N uptake, N use efficiency (NUE) and grain yield on bread wheat cultivars. Factorial combinations of five N levels (0, 30, 60, 90, and 120 kg N ha^-1) and four bread wheat cultivars (Danda’a, Digalu, Kakaba and local cultivar) were laid out as a randomized complete block design (RCBD) with three replications. The interactions of sites, N levels, and cultivars significantly (p ≤ 0.01) affected grain yield (GY), nitrogen uptake by grains, total nitrogen uptake, nitrogen uptake efficiency (NUpE) and nitrigen use efficiency for grain yield (NUEGY). Main effects of sites, N levels and cultivars had significant (p < 0.01) effect on grain and straw N contents, straw N uptake, N biomass production efficiency, N utilization efficiency (NUtE) and nitrogen harvest index (NHI). The cultivar Kakaba at rate of 90 kg N ha^-1 produced the highest grain yield (4880 kg ha^-1) in Tullo, which was statistically similar with the grain yield (4816 kg ha^-1) obtained from the cultivar Digalu with 120 kg N ha^-1 in Meta district. The NUEGY was higher with values of 24.2 and 24.1 kg grain kg^-1 N in Tullo and Meta districts, respectively, for Digalu cultivar at 30 kg N ha^-1 application rate than the remaining N levels and variety interactions at both sites. Cultivars variations in NUEGY under low N application levels were mainly due to higher variations in NUpE than in NUtE. Therefore, there is a need for exploration of the effectiveness of various combinations of N rates with time of applications for improvements of N-use efficiency traits and cost effectiveness in improved wheat cultivars production.

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