Effects of Water–Nitrogen Interaction on Sandy Soil, Physiology, and Morphology of Tall Fescue ( Festuca arundinacea Schreb) Turf

The soil water and nitrogen (N) levels are the important factors affecting turfgrass growth. However, the impact of the water–N interaction on tall fescue ( Festuca arundinacea Schreb) in terms of the N metabolism and plant morphology remains uncertain. Therefore, the objective of this study was to investigate the impacts of different N and water levels on the physiological and morphological responses of tall fescue. The experiment was designed with N (N 0 , N 2 , and N 4 representing N application rates of 0, 2, and 4 g m –2 , respectively) and irrigation [W 1 , W 2 , W 3 , W 4 , and W 5 representing field water capacities (FWCs) of 90~100%, 75~85%, 60~70%, 45~55%, and 30~40%, respectively] treatments, and the relevant indexes of the soil water content and soil NH 4 + –N and NO 3 − –N levels as well as the physiology and morphology of the tall fescue were determined. The results demonstrated significant changes in the contents of soil water (SWC) and N and the physiological and morphological indexes, except for the enzymes related to N metabolism, including nitrite reductase (NiR), glutamate dehydrogenase (GDH), and glutamate synthetase (GOGAT). The water stress significantly enhanced the water and N use efficiencies (WUE and NUE), except the NUE in the W 5 treatment. The N stress significantly influenced the SWC, soil NO 3 − –N content, and physiological and morphological indexes, excluding malondialdehyde, NiR, GOGAT, and above- (AGB) and below-ground biomass, resulting in the increased WUE and NUE. The application of a low N rate effectively alleviated the detrimental impacts of water stress on the SWC and glutamine synthetase activity. In conclusion, W 2 and N 2 are deemed more appropriate treatments for the low-maintenance measures of tall fescue turf. Among all the treatments, N 2 W 2 is recommended as the optimal water–N interaction treatment due to its ability to conserve resources while still ensuring high turf quality.