Large biomass and kernel yield responses to phosphorus (P) of
‘Challenger’ sweet corn crops grown at Lincoln, New Zealand on a
lowP site (Olsen P=6gml−1) have been reported, although HIwas
unaffected (Fletcher et al., 2006). Subsequent analysis attributed
most of the yield differences to changes in the spatial and temporal
patterns of accumulated intercepted solar radiation (MJm−2, RIcum)
for these crops in response to P supply (Fletcher et al., 2008). Differences
in RIcum were caused by both a delay in leaf appearance and
a decrease in the area of individual leaves of the P deficient crops.
However, changes in biomass and kernel yield may also result from
differences in crop radiation use efficiency (g MJ−1; RUE)
RUE is a simple measure of carbon assimilation integrated over
the whole crop canopy (Sinclair and Horie, 1989). Leaf photosynthetic
rates are generally instantaneous measurements, whereas
crop biomass measurements for calculation of RUE are usually