G. Belanger et al., CARBON BALANCE OF TALL FESCUE (FESTUCA-ARUNDINACEA SCHREB) - EFFECTS OF NITROGEN FERRITIZATION AND THE GROWING-SEASON, Annals of botany, 74(6), 1994, pp. 653-659
The C balance of a tall fescue sward grown under different rates of N
fertilization in summer, autumn, and spring was calculated using model
s derived from measurements of shoot growth, canopy gross photosynthes
is, shoot respiration and of C partitioning to the roots. Under the di
verse growing conditions associated with the seasons and the N fertili
zation, C utilization for above- and below-ground biomass accumulation
never exceeded 39 and 14% of the canopy gross photosynthesis, respect
ively. Carbon losses attributed to root respiration and exudation, whi
ch were estimated by difference between canopy net photosynthesis and
total growth, ranged between 3 and 30% of canopy gross photosynthesis.
Seasonal differences in shoot growth could be attributed to the amoun
t of intercepted radiation, the radiation-use efficiency and the C par
titioning to the roots. The effect of N deficiency on shoot growth can
be attributed to its effects on canopy photosynthesis (principally re
sulting from changes in intercepted photosynthetically active radiatio
n) and C partitioning. In comparison with the effect on shoot growth,
the effect of the N deficiency on the canopy gross photosynthesis per
unit of light intercepted over the regrowth cycle was limited. It is c
oncluded that most of the effect of N fertilization on shoot growth is
due to changes in C partitioning which result in faster leaf area dev
elopment and greater light interception.