THE EFFECTS OF NITROGEN-FERTILIZATION AND THE GROWING-SEASON ON CARBON PARTITIONING IN A SWARD OF TALL FESCUE (FESTUCA-ARUNDINACEA SCHREB)

The effect of N fertilization on the relative carbon partitioning to the roots of tall fescue (Festuca arundinacea Schreb), grown under field conditions, was studied with a 14C-labelhng technique on three regrowths representing contrasting growing seasons Under non-limiting N growing conditions, the relative carbon partitioning to the roots averaged 17-0, 15 8, and 11 1% in the summer, autumn, and spring regrowths, respectively The relative carbon partitioning to the roots increased during the summer and autumn regrowths but decreased during the spring regrowth In the absence of N fertilization, the relative carbon partitioning to the roots averaged 31 3,26 5, and 26 7 % in the summer, autumn, and spring regrowths, respectively The results were interpreted in terms of a functional equilibrium between the shoots and the roots It was concluded that, for a dense canopy of a perenmal grass growing under fluctuating conditions of solar radiation and temperature, the relative growth of the roots compared to the relative growth of the total biomass is primarily a function of the shoot biomass. © 1992 Annals of Botany Company.