![]() Loss of N also contributes to significant direct economic losses to the grower particularly when N fertilizer costs are high. The remainder of the applied N is lost to the soil through leaching and runoff, where the often excessive application can affect natural ecosystems through N pollution. However, nitrogen use efficiency (NUE) in cereals is generally poor, where it is estimated that only 30–40% of the total of N-fertilizers applied are actually harvested in the grain. In addition, the Ethiopian Vertisols tend to exhibit low total N content mainly due to leaching and denitrification limiting wheat production hence, application of N is one of the major inputs used by farmers to achieve desired crop yields on these soils. These soils are characterized by very low water infiltration rate or low saturated hydraulic conductivity and, therefore, are susceptible to waterlogging under high-intensity rainfall conditions. Vertisols occupy about 12.6 million hectares in the country where 7.6 million ha was found in the highlands. The low yield of wheat in the country may be due to the use of low-yielding varieties, inadequate and erratic rainfall, diseases, low soil fertility and waterlogging in the Vertisol areas. Despite the long history of wheat cultivation and its importance to the Ethiopian agriculture, its average yield is still very low, not exceeding 2.4 t ha −1 which is below the world’s average of 3.4 t ha −1. Out of the total grain crop area, wheat ranked 4th after tef ( Eragrostis tef), maize ( Zea mays) and sorghum ( Sorghum bicolor), while third in total production after maize and tef. It is one of the major cereal crops grown in the highlands of Ethiopia, and the country is regarded as the largest wheat producer in Sub-Saharan Africa. All wheat varieties tested did not show a significant variation in most of the nitrogen use efficiency parameters, and these efficiency parameters decreased with the increasing rate of N beyond 120 kg ha −1 in both growing seasons.īread wheat ( Triticum aestivum L.) is one of the most important cereal crops of the world and is a staple food for about one third of the world’s population. ![]() Hence, it could be concluded that varieties Menze and Tsehay produced the highest grain yield followed by variety ET-13. The highest apparent nitrogen recovery efficiency was recorded for variety Tsehay at N rate of 120 kg ha −1 in both growing seasons. The highest grain and straw (2.7 and 0.35%, respectively) nitrogen concentration were produced by variety Tsehay at N rate of 360 kg ha −1. The highest grain yield (5718.32 kg ha −1) was obtained from variety Menze at N rate of 360 kg ha −1 in 2015 which was statistically at par with the application of 240 kg N ha −1 and with variety Tsehay at N rate of 240 and 360 kg N ha −1 during the same growing season. The three-way interaction of year, N fertilizer rate and variety significantly affected ( P < 0.01) grain yield, grain and total nitrogen uptake, agronomic efficiency, agro-physiological efficiency and apparent recovery efficiency. The interaction of year and variety and N rate and variety affected grain and straw nitrogen concentrations, respectively. The two-way interaction of year and N rate, N rate and variety significantly affected grain nitrogen concentration. The treatments consisted of a factorial combination of four rates of nitrogen (0, 120, 240 and 360 kg ha −1) and three popular wheat varieties (Menze, Tsehay and ET-13) in a randomized complete block design with four replications. ![]() Therefore, a field experiment was conducted for two consecutive years (20) to evaluate the effect of N application rates on grain yield, nitrogen uptake and N use efficiency of bread wheat varieties. Application of a large amount of N fertilizer has been a method of increasing yield in the study area which is costly and can cause environmental pollution. ![]() Nitrogen is one of the most important nutrients limiting yield of bread wheat in Ethiopian highlands.
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