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(TLIMATE AND CROP PRODLFCTR-‘YTY
IN ALlSTR.»\Llr»’\
tion if desired. In the Australian context it is being used as a first-order sieve of
postulated crops andfor cropping systems at continental scale. It is the most
generalized model in an intended hierarchy of models of increasing complexity‘.
At the level of management. invohring such control variables as population.
geometry. nutrient application, and irrigation a much more comprehensive
model of the entire course of crop growth and development is required. Such a
model has been conceptualized. developed. and programmed by my colleagues
Douglas Cocks. David Morris, and myself and is now being tested and further
developed by John Angus.
This model, NlCKOX. includes all major processes and simulates. on a daily
basis. the entire course of grmvth and development. Again, as with CROPEVAL
at a simpler level. the objective has been to provide a conceptual and structural
framework which can be readily adapted to any specified crop-site-management
situation. A simplified flowchart showing the more important components and
feedback mechanisms incorporated in the model is shown in Fig. 4.
One of the positive benefits of the systems approach is that it highlights what
is not known! Of the components processes outlined in Fig. 4. only photosyn»
thesis is understood reasonably well. The other major driving process. here
tenned morphogenesis, is identified as having a key role. The timing and rate of
initiation of growing points coupled with supply ofearbon and nitrogen (and the
balance between them) to these developing organs determine the ultimate
structure of the crop system.
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4» Flow chart showing component processes. causal pathways. and feedback mechanisms
incorporated incorp in the crop growth and development model. NICKOX.