Optimizing Wheat (Triticum aestivum) Water Productivity and Nitrogen Use Efficiency in Sandy Soils Using Water Retention Polymers with Improved Nitrogen Fertilizers

A field experiment was carried out in the research area of Fertilizer Research Centre, Faisalabad, Pakistan, during 2022–2023 to explore ways to improve crop performance indicators i.e., water productivity and nitrogen use efficiency in sandy soils, which typically degraded to retain water. The study evaluated and compared the use of water retention polymers (WRPs) along with different types of nitrogen fertilizers, including standard urea and neem-coated urea (NCU) to investigate interactive effects of different treatments on water productivity and nitrogen use efficiency (NUE). Treatments were control (first treatment and second treatment), first treatment applied standard urea (SU; 185 kg ha^-¹) without WRP, while second treatment applied NCU without WRP or SU with application of P: K (124:62 kg ha^-¹) while remaining treatments were applied with SU combined with WRP at different amounts 12 kg ha^-¹ (third treatment), 16 kg ha^-¹ (fifth treatment), or 20 kg ha^-¹ (seventh treatment), and with Neem Coated Urea combined with WRP at different amounts 12 kg ha⁻¹ (fourth treatment), 16 kg ha^-¹ (sixth treatment), or 20 kg ha^-¹ (eighth treatment) respectively. The study also assessed how varying rates of WRPs affected wheat yield and related traits, by statistical analysis using the Randomized Complete Block Design (RCBD). For an accurate assessment of the treatment’s effect, Tukey’s test was applied. Optimum water productivity and Irrigation Water Use Efficiency (IWUE) were recorded in eighth treatment (1.282 kg m^-³ and 12.82 kg ha^-¹ mm^-¹), but at the cost of reduction in yield. Optimum NUE was also obtained in fifth treatment (23.6). SU significantly improved yields compared to NCU, primarily due to nutrient leaching. SU combined with WRP outperformed NCU in NUE, IWUE, water productivity and yield performance, highlighting the importance of WRPs and nitrogen fertilizers in sandy soils. The study revealed that WRPs significantly improved soil moisture retention, reducing irrigation water demands, and thus, were helpful in decision making to achieve maximum yield under full water availability or maximum IWUE under water scarcity conditions.