Impacts of Nitrogen Fertilization on Hybrid Bermudagrass During Deficit Irrigation

Fertilizer application is a critical component of turfgrass management as it influences growth, color, stress tolerance, and overall quality. However, limited information exists on how fertilizer application, particularly nitrogen (N), affects hybrid bermudagrass performance and actual plant evapotranspiration (ETa) in both well-watered and deficit irrigation scenarios. A 7-week greenhouse experiment was conducted over two replicated runs to evaluate responses of ‘TifTuf’ hybrid bermudagrass (Cynodon dactylon × C. traansvalensis Burtt Davy) to three nitrogen rates (0, 2.4, and 4.8 g N m−2 month−1) and three irrigation levels (1.0, 0.65, and 0.30 × ETa). Fertilized turfgrass exhibited 11–12% greater ETa compared to unfertilized turfgrass, with no significant differences between the two fertilizer rates. Under well-watered conditions (1.0 × ETa), the high nitrogen rate significantly improved visual quality (7.8) relative to the unfertilized control (7.1) and the low-rate treatment (7.4). High-rate fertilizer application significantly enhanced visual quality at both deficit levels (7.2 and 6.6, at 0.65 and 0.30 × ETa, respectively) compared to the unfertilized control (6.2 and 5.9, at 0.65 and 0.30 × ETa, respectively). At 0.30 × ETa, low-rate fertilizer application also significantly improved visual quality (7.0) compared to the unfertilized control. Soil nitrate-N levels increased with higher nitrogen application (1.30 ppm, 0.48 ppm, and 0.37 ppm, respectively, for high-rate, low-rate, and unfertilized), and shoot tissue analysis revealed greater N concentration in fertilized turfgrass (1.51%, 1.24%, and 0.85%, respectively, for high-rate, low-rate, and unfertilized). Clipping production and water use efficiency (WUE) were also improved with fertilization, although root development was hindered at the 0.30 × ETa irrigation level. These findings demonstrate that nitrogen fertilization improves visual quality, shoot growth, WUE, and drought response; however, tradeoffs such as elevated water use and nitrate-N leaching risk necessitate careful management to balance turfgrass performance with water conservation and ecosystem service preservation.