This work was carried out with the aim of defining nitrogen fertilisation strategies in pastures of Tifton 85 grass, based on monitoring dynamic changes in the structure of forage canopies. The experiment was carried out in an area of Planossolo in the experimental field of the Federal Rural University of Rio de Janeiro, during the pasture establishment phase. The treatments consisted of four levels of N (0; 50; 100 and 150 kg N-urea.ha-1), in a single application, arranged in 4 x 4 m plots, arranged in entirely randomised blocks, with four replications. Together with the nitrogen fertiliser, the plots received 80 kg P.ha-1 and 150 kg K.ha-1. The soil was corrected with 1.0 tn.ha-1 of limestone. The variables studied were: frequency of plant occurrence; canopy height, leaf growth and leaf area index (LAI), interception of photosynthetically active radiation (PAR) and dry matter production and partitioning.