A mathematical crop growth model for a mixed stand of Italian ryegrass (Lolium multiflorum L. and white clover (Trifolium repens L.).

[摘要] The main aim of this study was to develop a mathematical crop growth model for a mixedstand of ryegrass and clover. The modelling exercise consisted of an experimental componentas well as the actual modelling component. The experimental part of the project was essentialin terms of gaining a better understanding of the competitive Interactions between ryegrass andclover, as well as being essential for obtaining all the necessary parameters and variables forthe model.The experimental results of the project revealed that a.':though the single leaf photosyntheticrates of clover were higher than those of the ryegrass, the clover was outcompeted by theryegrass in mixed swards. This was due to the better eanopy structure and quantum yieldefficiency of ryegrass relative to clover, It was also found that environmental temperature andincreasing levels of interspecific competition strongly influenced the growth rates and carbonallocation coefficients of these crops. The interspecific competition experiment showed thatryegrass benefitted from its interactions with clover, while clover was detrimentally affected.This experiment also indicated that a transfer of nitrogen occurred from the clover to theryegrass.The model was based on the assumption that the canopy structures and quantum yieldefficiencies of the respective crops would largely influence their competitive abilities. Themodel was unique in that it was a mixed crop growth model which accounted for theenvironmental effects of fluctuating temperature and irradiance on photosynthetic rates,the model was found to simulate the growth of ryegrass and clover, both in monoculture andin mixture, to satisfaction.

[发布机构] University of the Witwatersrand