‘‘normal’’ or TOS1 (late
May or early June) and ‘‘late’’ or TOS2 (mid or late June). The four
combinations of two levels of [CO2] and two sowing times were
allocated to the 16 rings with four replicates. Each ring consisted
of two plots (4 m long 1.8 m width) and the plots were sown
in eight rows of 0.21 m space between rows and 0.1 m space within
rows.