Predicting frequency distributions in crops of carrot (Daucus carota L.) and red beet (Beta vulgaris L.)

Ability to predict variation in individual storage root size is essential as most root vegetables are marketed in diameter grades. There are, however, few methods that allow variability in size to be predicted. This paper describes a method for carrots and red beet, which uses a normal frequency distribution of the logarithm of each root weight plus a constant. The parameters of this distribution were relatively constant, or well correlated with the mean weight for several carrot and red beet data sets. This simple model was tested on independent data sets and there was a close agreement between observed and predicted yields in weight grades for carrots. Predictions for yields of grades of commercial interest were little affected by changes of 10% in the values of the parameters. In red beet, the independent data had been graded for diameter. Using weight grades corresponding to the diameters, a close prediction for yields in each grade was found. Thus, models that can predict mean weight of a carrot or red beet crop can be used in conjunction with the model described here to estimate yield in weight grades. Yield in diameter grades may then be estimated, if weight - diameter relations are available.