This research was conducted with the objective of determining growth of Brachiaria brizantha (A. Rich.) Stapf. cv. Marandu under nitrogen (N) rates (28, 112, 210, 294 and 378 mg/L, where N-NO3- : N-NH4+ of 70%:30% proportion was kept constant) and growth ages (21, 28, 35, 42, 49 and 56 days after seedling emergence). The experiment was carried out in greenhouse conditions, with nutrient solution and using ground quartz as substrate. The experimental design used was a complete randomized block design, with treatments arranged in a 5x6 factorial, with four replications. Nitrogen rates and growth ages interaction was significant for all growth attributes of Marandugrass, except for the mean net assimilation rate (NAR). The results showed that the maximum values for the relative growth rate (RGR) and absolute growth rate (AGR) were 0.25 g/g.day and that was observed at 28 days with N rate at 378 mg/L, and 3.68 g/day at 56 days associated to N rate at 378 mg/L, respectively. At 21 days of growth, occurred maximum values of 2.16 dm²/g at the highest N rate for leaf area ratio (LAR), of 0.48 g/g with N rate at 294 mg/L for leaf weight ratio (LWR), and of 5.14 dm²/g for specific leaf area (SLA) at N rate of 378 mg/L.
Brachiaria brizantha; leaf area ratio; leaf weight ratio; net assimilation rate; relative growth rate; specific leaf area
