Defoliation Dynamics in Kikuyugrass Pastures Subjected to Intensities of Defoliation

Abstract

Some recent papers have recommended moderate intensities of defoliation in order to maximize herbage intake at different time-scales. Most of them, however, did not assess the grazing dynamics of individual tillers during the stocking period. Therefore, the objective of this work was to describe the defoliation dynamics of kikuyugrass (Pennisetum clandestinum Hochst ex. Chiov) pastures subjected to different intensities of defoliation (40, 50, 60, and 70% of the initial height). Twelve 1500 m2 plots were strip-grazed over 24 h, and the frequency and severity of defoliation of individual tillers were assessed in 40 tagged tillers per experimental unit. From these data (n = 1920), we calculated the grazed area in the upper, second, and third horizon, and the total grazed area. We found that the frequency of defoliation by leaf category (expanding, mature, and senescent) increased linearly with the intensity of defoliation, and that reductions in extended tillers could not be used as a proxy to estimate the frequency of defoliation. Moreover, 22% of the second and third horizons were already exploited with intensities of defoliation of 40%, raising the possibility that the exploitation of lower grazing horizons could be more related to stocking density and relatively independent of the grazed area.

Keywords

• frequency of defoliation
• grazed area
• grazing horizons
• severity of defoliation
• tiller