Banca de QUALIFICAÇÃO: BRUNA EDUARDA MOREIRA FEIO

RECOVERY OF PASTURE WITH MARANDU GRASS USING FERTILIZATION WITH NITROGEN AND PHOSPHORU

Degradatiom; Foragem; Fertilization

The genus Urocloa brinzantha cv. Marandu stands out in the agricultural scenario, occupying approximately 50 to 70% of the pastures cultivated in Brazil. However, the lack of nutrient replacement has become one of the main causes of pasture degradation. Thus, macronutrients such as nitrogen and phosphorus are the main responsible for the increase in productivity and maintenance of forages. Through the combination of nitrogen and phosphorus, the objective was to study the effect of these macronutrients on the recovery of pasture with marandu grass. The experiment was carried out on a rural property located in the municipality of Bujaru, state of Pará. The experimental design was established in randomized blocks, in a 4 x 4 factorial scheme, with sixteen treatments and three replications, totaling 48 experimental units, with the treatments distributed as follows: four N doses (0; 100; 200 and 300 kg ha-1) and four P doses (0; 50; 100 and 150 kg ha-1). The N source used was ammonium sulfate (21% N - first application) and urea (45% N) in maintenance fertilization and as a P source, simple superphosphate (18% P2O5), in which the treatments were applied in June/2023, in which the plants were subjected to seven cuts. After the experiment was completed, soil samples were collected using a Dutch auger at a depth of 0-20 cm to evaluate the effect of the application of treatments on the chemical properties of the soil. The experimental results showed that the interaction between nitrogen and phosphorus influenced dry matter production, as well as dry matter content, tiller density and grass height. However, the accumulation of nitrogen and phosphorus, both in the soil and in the plant, was determined by the individual doses of these nutrients. Thus, based on the variables mentioned, it can be inferred that the best responses for phosphorus and nitrogen are between 90 and 150 kg ha-1 of P2O5 and 200 and 250 kg ha-1 respectively, providing an increase in the productivity of marandu grass, as well as demonstrating the importance of nitrogen and phosphorus fertilization management for soil fertility variables in the availability of nutrients in the soil-plant system.