A model to predict the effects of complex row spacings on the yields of root crops

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Abstract
SUMMARY: A mathematical plant competition model developed by Currah (1975), and subsequently modified by the author, is briefly described. The model has two useful properties: (a) it can cope with complex irregular row spacing systems such as occur in commercial practice and (b) it can be ‘calibrated’ to the yield values at any site by using data from previous crops.Parameter values of the modified model are calculated for both carrot and red beet crops. At least 70% of the variation in these data could be accounted for by fitting the model, a performance which was similar to, but never as good as, fitting analysis of ariance models. There were no systematic deviations between the fitted and observed values.Previously estimated parameter values were used to predict mean root weights of carrot and red beet storage roots. Overall agreement between predicted and observed data was good, although some systematic deviations occurred.The practical value of the modified version of the model and its strengths and weaknesses are discussed.