Effects of different nitrogen treatments on the growth and carbon-nitrogen metabolism of tall fescue under low-light stress

The application of nitrogen fertilizers has a notable effect on the quality of lawns under low-light stress. To investigate the effects of low light and different nitrogen levels on the growth and carbon–nitrogen metabolism of tall fescue (Festuca arundinacea), two light levels (normal light and low light) and three nitrogen levels: low nitrogen (1 mmol·L⁻¹), moderate nitrogen (6 mmol·L⁻¹), and high nitrogen (18 mmol·L⁻¹) were investigated. To provide a theoretical basis for urban landscaping and the management of lawns, the effects of light and nitrogen interactions on the morphology, physiology, and carbon–nitrogen metabolism of tall fescue were studied. The results showed that, compared to normal light exposure, the tiller number, leaf width, total biomass, soluble sugar content, soluble protein content, and nitrate reductase activity decreased in tall fescue under low light. Furthermore, the low nitrogen treatment could induce good blade width and increased the root cap ratio, carbon and nitrogen ratio, and the activity of glutamine synthetase in tall fescue under low-light stress. However, compared to the normal light treatment, the difference in tiller number and soluble sugar content of tall fescue under low light conditions was lower. Compared to the moderate or high nitrogen levels, the total biomass, nitrate reductase activity, and total carbon content of tall fescue under the low nitrogen treatment were not significantly different. Therefore, under low-light stress, tall fescue treated with low amounts of nitrogen had a good appearance and environmental adaptability, and the carbon–nitrogen metabolism of the plant tended to be balanced, which was conducive to the ideal growth of the plant.