Agriculture Reference
In-Depth Information
Fig. 9.3 Scheme illustrating the determination of critical N concentration (N
mcrit
) in leaves and
proposed changes under elevated [CO
2
]. Concrete results reported in Conroy and Hocking (
1993
)
Fig. 9.4 Hypothetic nitrogen response curves (Mitscherlich curve
s
) of crops grown under ambient
and high [CO
2
]. N
sat
indicates sufficient N supply to achieve 90 % of maximum growth or yield. Y
i
indicates yield without additional (fertiliser) N, Y
ii
denotes yield after a certain fertiliser applica-
tion (
arrow
). It is not resolved whether and under which conditions N
sat
changes under elevated
[CO
2
]. Agronomic efficiency of fertiliser application can be calculated as the difference between
yields with and without fertiliser (Y
ii
-Y
i
) divided by the fertiliser applied (Table
9.1
). In this
hypothetic system, agronomic efficiency of the fertiliser applied (
arrow
) would be greater under
elevated than ambient [CO
2
], because the yield difference is greater at the higher N application
