Regression equations to estimate leaf area of kale.

Abstract

Kale is one of the most popular vegetables in the Brazilian middle-south region. Leaf area is a variable of fundamental importance for studies of growth analysis, plant nutrition and phenology viewing the establishment of adequate cropping techniques. Therefore, the aim of this work was to establish regression equations to estimate leaf area of kale (Brassica oleracea var. acephala), cv. Top Bunch. Forty leaves of kale in six classes of length (less or equal to 5 cm, between 5. and 0 cm, between 0. and 5 cm, between 5. and 20 cm, between 20. and 25 cm, and between 25. and 30 cm) were evaluated. Tests were applied for parallelism and coincidence of lines between the classes. The equations were adjusted to the models with intercept (Y = a + bx) and without intercept (Y = bx), and the F test was used to verify the best model. The regression models to estimate leaf area (LA) based on the product of length by width (CL) presented the best adjustment (high coefficient of determination and F value). But, for length classes of 5. to 0, 0. to 5, 5. to 20, 20. to 25, and 25. to 30 cm, the equations based on the width (W) can be used, because they show high coefficient of determination and permit a faster collecting of data.Additional keywords: Brassica oleracea var. acephala; prediction models; nondestructive method.