The Use of a Mathematical Model for the Analysis of Manurial and Weather Effects on the Growth of Carrots

Publisher Website
Google Scholar
Abstract
A model for the study of yearly and other variation in crop yields, based on a generalized form of the logistic equation of growth, was applied to three years' growth analysis data on carrot crops from 16 plots of a long-term manurial experiment. In the ideal case, it is postulated that the growth in different years of carrot leaves or taproots on soil receiving a given manurial treatment could be described by a single curve if time in days was replaced by a scale based on one or more meteorological elements which affect relative growth-rates. The equation fitted the data on the growth of the leaves but not that on the taproots. For leaf growth, the use of the sums of solar radiation, day degrees or evaporation from an open water surface did not give curves that fitted the growth data better than those obtained with time in days. Yearly differences in leaf (but not taproot) growth appeared to be related to corresponding differences in rainfall amounts, and it is suggested that a scale taking account of soil moisture tension might have given a better fit to the model. It appeared that whereas the relative leaf growth-rate was a function of leaf but not taproot weight, relative taproot growth-rate was a function of taproot weight and leaf weight. A further model for the growth of carrots, based on this hypothesis is described.