Yield Productivity and Nitrogen Uptake of Wheat Crop Are Highly Dependent on Irrigation Water Availability and Quality under Water-Limited Conditions

The water scarcity can limit yield productivity of wheat, and this issue can be controlled using various management practices. The main objectives of this study were: 1) to investigate how N application rates and water quality affect the yield productivity, and plant growth characterization and nitrogen uptake of wheat crop under water-limited conditions; 2) to describe the relationships between nitrogen application rates and yields of wheat plants at low-quality water application times; 3) to predict the efficiencies of applied N fertilizers at different rates and water use efficiency. Field experiments on wheat crop were conducted for two consecutive growing seasons (2016–2017) at a private farm at Abis-Alexandria. The experimental design was split-plot design with three replicates. The main plot was nitrogen application rates (0, 75, 150, and 225 kg N ha−1) in the form of urea fertilizer (46% N). The sub-main plot was low-quality water application (LQW) (0%, 25%, 50%, and 75% from applied water requirements of wheat crop) co-applied with high-quality water (HQW). The obtained results indicated that the application of nitrogen fertilization with different rates significantly increased the economical and biological yields, grain/biological-nitrogen use efficiency, agronomic efficiency, nitrogen uptake, and water use efficiency for both grain and biological yields in the two seasons of cultivations. Moreover, the yield attributes such as spike length, number of plants and tillers were also significantly affected by N fertilization. Application of LQW at 25% and 50% co-applied with 75% and 50% HQW did not significantly decrease the yield and yield attributes of wheat in both seasons of cultivations. In contrast, the application of LQW at 75% co-applied with 25% HQW was significantly decreased the studied parameters. In conclusion, the best application ratio of LQW and HQW was 1:1 at 50% of LQW co-applied with 50% HQW at which the yield and its attributes of wheat did not significantly reduced.