Effect of salinity and nitrogen status on nitrogen uptake by tall fescue turf

Nitrogen (N) absorption is inhibited by root zone salinity, which could result in increased NO3 leaching. Conversely, N absorption is enhanced by moderate N deficiency. Because turfgrasses are grown under N-limiting conditions, it is important to understand the interactive effects of salinity and N deficiency on N uptake. This study examined the effect of N status (replete versus deficient) and salinity on N ((NO3)-N-15 and (NH4)-N-15) uptake and partitioning by tall fescue (Festuca arundinacea Schreb.). Two cultivars ('Monarch' and 'Finelawn I') were grown in nutrient solution culture. Treatments included N level (100% or 25% of maximum N demand) and salinity (0, 40, 80, and 120 meq L-1) in a factorial arrangement. Absorption of NO3 and NH4 was greater in low-N than in high-N cultures, but was reduced by salinity under both N treatments. Salinity reduced partitioning of absorbed N to leaves and increased retention in roots. These results suggest that turfgrass managers should consider irrigation water quality when developing their fertilizer program.