Optimizing Drip Irrigation and Nitrogen Fertilization for Sustainable Wheat Production in Arid Soils: Water–Nitrogen Use Efficiency

Water scarcity and inefficient nitrogen (N) use are major constraints on wheat production in arid regions. Drip irrigation offers a precise method for optimizing water and nutrient delivery, but integrated management strategies are needed to maximize yield and resource use efficiency. In Egypt, water shortages and inadequate fertilizer necessitate effective resource management for sustainable agriculture and crop productivity. This study investigates the effects of integrated water and nitrogen fertilizer management under drip irrigation on wheat (Triticum aestivum L.) performance in arid zones of Egypt. A two-year field experiment was conducted to evaluate wheat yield, productivity of applied water (PAW), crop water productivity (CWP), and nitrogen use efficiency (NUE) under varying irrigation regimes and nitrogen application rates. This study evaluated two irrigation regimes: 100% (I1) and 80% (I2) of crop evapotranspiration (ETc) in combination with three nitrogen application rates: 142.8 kg N ha−1 (N1), 190.4 kg N ha−1 (N2), and 238 kg N ha−1 (N3). Irrigation at 100% of ETc (I1) significantly enhanced plant height, straw yield, biological output, grain yield, seed index, NUE, and CWP in comparison with the 80% ETc treatment (I2). However, I2 demonstrated a higher PAW and grain protein content than I1. Furthermore, applying nitrogen at a rate of 238 kg N ha−1 (N3) resulted in notable improvements in these parameters relative to the lower rate of 142.8 kg N ha−1 (N1). I1N3 and I1N2 treatments increased CWP by 29% and 22%, respectively, compared to I1N1 across both growing seasons. Principal component analysis (PCA) revealed that the application of 238 kg N ha−1 (N3) may represent the most effective nitrogen management strategy for optimizing winter wheat production under drip irrigation systems. Moreover, PCA suggested that combining deficit irrigation with a high nitrogen application rate (I2N3) enhances the productivity of applied water (PAW) and grain quality. In contrast, full irrigation with the lowest nitrogen rate (I1N1) appeared to be the most effective strategy for maximizing NUE. These findings highlight the potential of integrated strategies to sustainably boost wheat yields in environments suffering from water shortage.