Yield and Stability of Three Tropical Forage Grasses Cultivated as Pure or Mixed Stands

Abstract

Multispecific pastures are considered more sustainable to animal production than monocultures. However, studies on mixtures of tropical grasses are underexplored. We aimed to assess whether a mixture of three contrasting growth strategies of perennial tropical forage grasses could outperform their respective monocultures in terms of forage yield and stability. The four treatments included three perennial tropical forage grasses: Andropogon gambagrass (AG; Andropogon gayanus cv. Planaltina), Massai guineagrass [MG; Megathyrsus maximus cv. Massai] and Piatã palisadegrass [PP; Urochloa brizantha cv. BRS Piatã], cultivated as monocultures and as a mixture of the three species. Treatments were randomly assigned to sixteen 180 m² plots and managed intermittently under manual harvest at pre- and post-harvest heights of 35 and 17.5 cm, respectively, for 2 years. The botanical composition of the mixture remained relatively stable, with a predominance of MG (68.9%), followed by PP (20.1%) and AG (6.8%). Annual forage yield varied between years (p = 0.0017) with a difference of 3974 kg DM ha⁻¹ year⁻¹, but not according to treatments (p > 0.05) with an average of 23,012 kg DM ha⁻¹ year⁻¹. No effect was observed for the intra-annual forage yield variance among treatments (p > 0.05). The association among PP, MG and AG in a mixture allows species to coexist with a relatively stable botanical composition, as well as forage yield and stability, similar to their monocultures.