is well adapted to infertile and acid soils with poor drainage or temporary flooding (Keller-Grein et al. 1996). It is widely used in Brazil in wetlands and areas of marginal land characterized by waterlogged soils. During the evaluation stages of the breeding program of this species, genotypes are general-ly tested using consecutive cuts within different seasons for at least 2 years. The ‘Cerrado’ region, where most animal production takes place in Brazil, has 2 well de-fined seasons: spring-summer with warm weather and rain; and autumn-winter with cooler, dry weather. Thus, owing to environmental variation, especially related to climate, it is important to investigate the main effects of environmental factors (years and seasons), as well as interactions between genotypes and environmental fac-tors, in order to have greater confidence in the selection of superior hybrids of