Morphogenesis, Structure, and Chemical Composition of Paiaguás Grass Under Different Nitrogen Doses and Deferment Periods

The study evaluated the effects of nitrogen fertilization on the morphogenetic, structural, productive, and nutritional characteristics of Brachiaria brizantha cv. Paiaguás subjected to two stockpiling periods in a pot experiment. The experiment was conducted using a randomized block design in a 4 × 2 factorial arrangement, with four nitrogen doses (0, 25, 50, and 75 mg N dm−3, applied as urea) and two stockpiling periods (80 and 120 days). Increasing nitrogen doses promoted linear increases in leaf appearance, elongation, and senescence rates, as well as tiller population density, while reducing phyllochron and leaf lifespan. Forage mass increased linearly with nitrogen, ranging from 96.25 to 113.00 g of dry matter per pot, and leaf blade mass showed a similar response. Root mass exhibited a quadratic response, with a maximum estimated value of 49.33 g pot−1 at 60.18 mg N dm−3, this quadratic equation explained 96% of the variation in the results. No significant interaction was observed between nitrogen doses and stockpiling periods for dry matter, crude protein, mineral matter, or neutral detergent fiber contents. However, nitrogen fertilization increased crude protein content across plant fractions, with leaf crude protein rising from about 70 to over 110 g kg−1 dry matter. Nitrogen fertilization at 75 mg N dm−3 combined with an 80-day stockpiling period improves canopy structure, forage production, and nutritional quality of Paiaguás grass, highlighting the importance of synchronizing nitrogen supply with deferment duration in deferred pasture management.