Responses of Panicum maximmum cv. Tanzânia to fertilization rates and cutting heights associations.

Abstract

The sustainability of production systems depends on its ability in generating financial incomes for the producer, steadily over the years, promoting economic return from investments without incurring in deterioration of production environments. However, most of Brazilian pastures are under degradation or presents limited capacity to generate financial incomes due to inappropriate technology use. Grazing and soil fertilization management are critical points of this process. Nutrients cycle in grasslands involves nutrient extraction from the soil, within plant remobilization, nutrient recycling through litter decomposition and redistribution through animal excreta. Increases in defoliation severity and forage utilization can lead to increases in relative importance of recycling through animal excreta, which are subject to greater losses by leaching and volatilization, and to reductions in relative importance of remobilization, with greater proportion of nutrients being supplied by the soil. This process points to an interaction between plants cutting height and soil fertilization, affecting productivity of grazed swards. This experiment aims to investigate the association between fertilization and defoliation intensity by combining two fertilization levels (zero and 400 kg N / ha / year), and three cutting heights (20, 30 and 50 cm). Cutting is going to be done by beef cattle in a Mob Grazing experiment model, every time that light interception (LI) by the canopy achieves 95%. IT is intended to be evaluated: nutrient extraction by plants, forage total accumulation, forage accumulation rates, forage losses and grazing efficiency. Besides that, it is intended to examine the LI x Sward height and LI x tillering relationships, and to describe forage accumulation process.