The objective of this study was to determine an empirical mathematical model to estimate leaf area in rice cultivars from linear leaf dimensions, with an emphasis on modern and recently cultivars used by farmers in Brazil. Through the leaf dimensions it is possible to estimate the final yield of the crop from the leaf area index. Therefore, the size of the leaves is closely related to the production of photoassimilates that will be converted into grain yield. For this, field experiments were carried out in Santa Maria, Restinga Seca, Itaqui and Cachoeirinha with three hybrids and twelve conventional cultivars in four growing seasons (2013/14, 2014/15, 2015/16 and 2016/17). Twenty five leaves of each cultivar were used to calibrate the model and others twenty five leaves were used to test the predictive capacity of the model as independent data. The model is based on the length (L) and the largest width (W). The relationship between leaf area and linear dimensions was fitted to a linear model for each cultivar as well as to a generalized model for all cultivars. The predictive capacity of the equations was evaluated with statistics Root Mean Square Error (RMSE), BIAS, modified index of agreement and coefficient r. The results indicate that the non-destructive method, based on the linear dimensions of the leaves, is appropriate for estimating the leaf area in rice and that the general equation LA = 0.78 (L.W.) can be used for several modern rice cultivars in Brazil.

Keywords: Oryza sativa, leaf area index, non-destructive method, linear dimensions