Yield and Nutrient Use Efficiency of Bread Wheat (Triticum Aestivum L.) as Influenced by Time and Rate of Nitrogen Application in Enderta, Tigray, Northern Ethiopia

Wheat is an important staple crop in arid and semi-arid areas of the Tigray region of Ethiopia. However, the yield and quality of the crop is markedly constrained by low soil fertility, inappropriate rate and timing of nitrogen application. Therefore, an experiment was conducted to elucidate the effect of different rates and timing of nitrogen fertilizer application on the yield, quality, and nitrogen use efficiency of bread wheat varieties during 2013 and 2014 main cropping seasons. The treatments consisted of four rates of nitrogen (23, 46, 69, and 92 kg N ha-1), three timing of N application (½ at sowing + ½ at tillering, ¼ at sowing + ½ at tillering + ¼ at anthesis, and 1/3rd at sowing + 1/3 rd at tillering + 1/3rd at anthesis) and two bread wheat varieties (Picaflor and Mekelle I) and 0 kg N ha-1 (control). The experiment was laid out as a randomized complete block design in a factorial arrangement with three replications. During both cropping years, increasing the rate of nitrogen application up to 69 kg N ha-1 significantly (P< 0.01) increased the total aboveground biomass and grain yields of the crop and decreased with further increase of applied N fertilizer. The highest aboveground biomass (6871 kg ha-1) and grain yields (2775 kg ha-1) of the crop were obtained in response to the application of 69 kg N ha-1, in 2013. The equivalent value for total aboveground biomass and grain yields during 2014 cropping season were (8815 kg ha-1and 3695 kg ha-1), respectively . The highest apparent recovery efficiency of 75% was obtained in response to the rate of 69 kg N ha-1applied in three splits of 1/4 at planting, ½ at tillering, and 1/4 at anthesis. The equivalent values for the highest apparent recovery was 81% in the 2014 cropping season. The highest agronomic efficiency of 25 kg kg-1 and utilization efficiency of 55 kg kg-1 were recorded at the rate of 46 kg N ha-1 in three splits of 1/4 at planting, ½ at tillering and ¼ at anthesis. The equivalent values in 2014 were 34 kg kg-1 and 78 kg kg-1, respectively. Grain protein concentration increased from 10.57% to 11.82% in 2013 and from 8.97% to 9.84% in 2014 cropping season as the rate increased from 23 kg N ha-1 to 69 kg N ha-1. The acceptable marginal rate of return (1618%) and highest net benefit (34141ETB ha-1) was obtained from 69 kg N ha-1 for the variety Picaflor. In conclusion, applying 69 kg N ha-1 in three splits of ¼ at planting, 1/2 at tillering and ¼ at anthesis resulted in optimum grain yield, protein concentration and economic return of the crop