Tillering dynamics in massai grass fertilized with nitrogen and grazed by sheep

Abstract

To evaluate the tillering dynamics of massai grass under rotational sheep stocking and fertilized with nitrogen (control - 0; 400; 800 and 1200 kg ha^-1 year^-1), this study was carried out, in a completely randomized design with repeated measures over time. The mob-grazing technique was applied to perform the grazing by employing groups of animals for rapid defoliation. The tiller appearance, survival and mortality rates, tiller biomass, and green/dead tillers ratio, have presented increase responses to nitrogen levels, with the three rates and the tiller biomass varying between evaluation periods. There was a quadratic response for the tiller flowering rate, population density of vegetative and reproductive tillers, reaching maximum values (0.051 tiller 100 tiller^-1 day^-1; 4,818 and 35 tillers m^-2, respectively) under the nitrogen levels of 613.5; 993.5 and 623.9 kg ha^-1 year^-1, respectively. For the tiller flowering rate and population density of reproductive tillers, it was verified a fluctuation between periods. The nitrogen fertilization promotes positive changes in tillering dynamics of massai grass, allowing the use of up to 800 kg ha^-1 year^-1 for maintaining the pasture stability. The tillering demography of the forage had varied little between assessment periods.