Effects of nitrogen levels on the photosynthetic physiology and forage quality of bermudagrass

Nitrogen is an important component of proteins, nucleic acids, chlorophyll in plants. It is thus an essential nutrient element for plant growth, and different plants are known to have different nitrogen requirements. In this study, Cynodon dactylon ‘Wrangler’ was used as the experimental material to examine the effects of different nitrogen levels (N₁, N₂, and N₃) on photosynthetic physiology and forage quality based on nutrient solution hydroponics. The purpose of the study was to determine the optimal levels of nitrogen with respect to growth, photosynthesis, and forage quality. The results revealed that compared with the N₁ conditions, plant growth was better and plant height increased significantly (P < 0.05) under the N₂ and N₃ conditions. Moreover, there were significant increases in chlorophyll content, the chlorophyll fluorescence kinetic curve, F_v / F_m value, and other photosynthetic indices (P < 0.05). In addition, forage quality indices, including the crude fiber content, were significantly higher, whereas there was a significant reduction in the content of ash (P < 0.05). Overall, the best photosynthetic characteristics (PI_CS) of bermudagrass were detected in plants subjected to the N₃ treatment, and these plants had significantly higher contents of nitrogen and crude protein than those receiving the N₂ and N₁ levels of nitrogen (P < 0.05). The findings of this study therefore indicate that the 10 mmol·L^–1 level would be the optimal level of nitrogen application for ‘Wrangler’ bermudagrass. This information will accordingly provide theoretical guidance for the practical application of nitrogen for this crop.