Optimizing Nitrogen Fertilization for Barley Crop at Full and Deficit Irrigation in the Arid Region

Background: Nitrogen and water are two major limiting factors that affects the growth and yield of barley. Optimization of nitrogen application is crucial in enhancing barley yield and nitrogen use efficiency while minimizing the negative effects of its intense application on human health and the environment. However, the crop yield response to nitrogen application rates differ under different irrigation conditions owing to the complementary relationship between nitrogen and water. Therefore, it is vital to study the impact of different nitrogen application rates on improving barley growth and yield under full as well as deficit irrigation to select the best field management option, thereby enhancing sustainable agriculture. Methods: The present study investigated the impact of three nitrogen application rates [0 (control), 50 and 100 kgN/ha)] at two irrigation rates corresponding to 100% and 75% crop evapotranspiration (ET_c) on the growth, yield and nitrogen use efficiency of barley. Stable isotopic technique was used to determine the nitrogen use efficiency. Result: The nitrogen application rate enacted a significant impact on plant height, number of plants/m², number of spikes/m² biomass yield and nitrogen use efficiency; whereas irrigation rates significantly affected the plant height, number of plants/m², spike, length, number of spikes/m² biomass yield, grain and straw yield. In addition, a significant interaction between irrigation and nitrogen, was observed for all the studied parameters except plant height, spike length, straw yield and total nitrogen uptake. The deficit irrigation 75% ET_c with 50 kgN/ha presented the highest nitrogen use efficiency (37.56%), but the total biomass yield was reduced by 37% in comparison to 100% ET_c irrigation. Thus irrigation and fertilization combination of 100% ET_c with 50 kgN/ha was identified as the best irrigation and fertilization practice producing highest biomass yield, grain yield and straw yield in barley with a nitrogen use efficiency of 20.48%.