Defoliation patterns on a mixture pasture of forage sorghum and Alexandergrass

Detailing the morphogenic characteristics of tropical species that form mixed pastures allows a broader view of plant-animal interactions. The objective of this study was to evaluate the intensity and frequency of defoliation in a mixed pasture of forage sorghum (Sorghum bicolor (L.) Moench.) and Alexandergrass (Urochloa plantaginea (Link) Hitch.) grazed by beef heifers and maintained under continuous stocking. The experimental design was completely randomized with two treatments, five evaluation periods, and nine replicates (paddocks). The tillers in each treatment were identified and marked in the same experimental unit (paddock), considering the existence of the pasture mixture. The treatments included forage species, forage sorghum, and Alexandergrass along the pasture cycle. The defoliation intensity of the leaf blades was higher in forage sorghum than in Alexandergrass during the second and fourth evaluation periods. The defoliation frequency of general leaf blades (number of defoliations blade-1 day-1) was higher for forage sorghum (0.13) than for Alexandergrass (0.11; P=0.0001). Total leaf blade mass (kg dry matter ha-1) was higher and lower during the first and fifth evaluation periods, respectively. Alexandergrass maintained leaf blade mass during the last evaluation period, while forage sorghum started the preflowering phenological stage. There was a preference for forage sorghum, but Alexandergrass ensured greater longevity of the system, and mixed pastures of these species are recommended.