The simplest GCR is the LUE model, where carbon assimilation is simulated using the concept of light-use efficiency. The intensity of radiation, limited by temperature and the availability of soil water, determines soybean daily dry matter net production. Total carbon assimilation is allocated to leaf, stem, root or grains depending on the phenological stage. Soybean productivity is estimated based on the percentage of dry matter allocated to grains. The model operates in a daily time-step, and is fully described by Oliveira et al. (2013).