Ej. Van Oosterom et al., Simulating growth, development, and yield of tillering pearl millet II. Simulation of canopy development, FIELD CR RE, 72(1), 2001, pp. 67-91
Tillering is an important adaptive feature of pearl millet (Pennisetum amer
icanum L.) to the unpredictable growing conditions of dry areas of the semi
-arid tropics. Yet, this feature has largely been ignored in the developmen
t of simulation models for pearl millet. The objective of this paper is to
parameterise and validate a leaf area module for pearl millet, which dynami
cally simulates crop leaf area from the leaf area of individual axes throug
h simulating inter-axis competition for light, To derive parameters for the
model, four cultivars (contrasting in phenology and tillering habit) were
grown under well-watered and well-fertilised conditions across a range of p
lant densities in three experiments at two locations in India. For selected
plants, observations on the number of primary basal titters and on the num
ber of visible, fully expanded, and senesced leaves on each axis were made
twice a week throughout the growing season. Occurrence of panicle initiatio
n (PI) was observed in two experiments only, but data were complemented by
published and unpublished data, obtained for comparable cultivars. Paramete
rs were obtained for the time from emergence to PI as a function of dayleng
th, the leaf initiation rate, the rate of leaf and tiller appearance and th
e leaf senescence rate; parameters for leaf size were determined in a previ
ous paper. Our parameter estimates compared well with published data and we
re, with the exception of time to PI and leaf size, mostly independent of c
ultivar, axis and density. Genotypic effects on productive tiller number co
uld be attributed to differences in main shoot leaf size. Validation of the
leaf area module showed that the module adequately reproduced the effects
of density, photoperiod and genotype on the leaf area of individual axes an
d on productive tiller number. This was despite the fact that the reduction
in leaf area of non-productive tillers was achieved in the module through
a reduction in leaf size, whereas the crop reduced leaf area through a redu
ction in leaf number. Our results indicate that LAI of a tillering crop can
be simulated adequately by simulating LAI from individual leaf area and in
corporating the effects of competition for light. (C) 2001 Elsevier Science
B.V. All rights reserved.