Simulating leaf appearance in a maize variety

Abstract

The calculation of leaf appearance rate (LAR) is an important part of many crop simulation models. The objective of this study was to evaluate and compare a linear model (the Phyllochron model) with a non-linear model (the Wang and Engel, WE, model) for simulating LAR in a maize variety. A field experiment was carried out in Santa Maria, RS, Brazil, with seven sowing dates during two growing seasons (2005/2006 and 2006/2007). The maize variety BRS Missões was used in a randomized complete block design, with six replications. Plant spacing was 0.8 m x 0.21 m, and each plot had three 5 m rows. Three plants in the central row of each plot were tagged. The ligule (expanded) and tip leaf number was measured weekly on the tagged plants. The Phyllochron model, which assumes a linear response of LAR to temperature, and the WE model, which assumes a non-linear response of LAR to temperature, were used to calculate ligule and tip leaf number. Models coefficients were estimated using the data set callected in 2005/2006 and evaluation of the models was with the data set collected in 2006/2007 using the statistics root mean square error (RMSE), index of agreement (d) and accuracy of WE model relative to the phyllochron model (E12). The WE model was superior to the Phyllochron model for predicting leaf number, with an overall RMSE of 0.80 leaves for ligule leaf number and 1.29 leaves for tip leaf number.