Estimation of eggplant leaf area from leaf dimensions

Abstract

This paper explores diferent models of non-destructive leaf area estimates for Solanum melongela L. by the measure of leaf length (C) and blade width (L). The methodology involved eggplant cultivation in the greenhouse from March to June. Plant leaves were sampled at random throughout the growing season, totalizing 186 leaves, of which 98 were used to estimate the model parameters and 88 were used for model validation. The samples covered wide spectrum of leaf dimensions, in order to minimize root mean square error (RMSE). Leaves were sampled at 71, 79, 81, 85, 92 and 99 days afer transplanting. The highest possible numbers of leaf discs were obtained with a 25mm auger. Correlations were computed between the leaf area obtained by the discs method and the linear dimensions of L and C, the product of both (CL) and the square length multiplied by the width (C2L). Regression analyses for 20 models were tested, including quadratic, exponential, linear, logarithmic and power model, of which 12 had a high coefcient of determination (R2) value. The quadratic model (Y = - 5.78+0.4981CL–3.263.10-4CL2) and the power model (Y = 0.4395CL1.0055) showed the best estimates, with R2 of 0.964 for both, and RMSE of 33.2 and 34.4, respectively. With only one leaf dimension the quadratic model (Y = -63.5+10.492L+0.2822L2; R2 = 0.937; RMSE = 44.1) is an alternative, with little impact on the precision.