Silvopastoral systems that integrate trees on animal production units are reported to be a promising land-use activity. Research on methods of integrating trees into smallholder pasture systems for development of such systems in the tropics has, however, received little attention. In Panama, smallholder pastures are abundant across the landscape, but they are often extensive, degraded, overgrazed, and of low productivity. Based on the premise that integration of silvopastoral systems on degraded pastures might be an effective technology that is accessible and affordable for small-scale producers, this research was carried out on-farm for two years in central Panama to help devise best management practices for optimizing tree-seedling survival, reducing competition between seedlings and herbaceous vegetation, and managing effects of large trees on forage.
Three experiments were conducted. The first one examined seedling survivorship and herbivory of three tree species (Anacardium occidentale, Bombacopsis quinata, and Tectona grandis ) planted in three configurations (grouped in diagonals, in lines, and along fences). The second experiment examined the effects of herbaceous vegetation on the establishment of tree-seedlings. Seedling growth and biomass distribution to shoots and roots were evaluated in relation to four herbaceous removal regimes, which included removal of surrounding vegetation--both above- and below-ground. In the third experiment that focused on the effects of large, dispersed trees on forage characteristics, two tree species, Anacardium occidentale and Tectona grandis, were evaluated for their effects in terms of mass, digestibility, and botanical composition of the forage underneath.
Research results revealed that Anacardium occidentale seedlings survived best in grazed pastures and the fence planting configuration resulted in the lowest seedling survival. Seedling herbivory was greatest for Bombacopsis quinata, and cattle and leaf-cutter ants (Atta spp.) were the herbivores that browsed seedlings most. Tree seedlings performed differently under the different herbaceous vegetation removal regimes. Bombacopsis quinata grew best overall and maintained a consistent root:shoot ratio during the two years of study. However, Anacardium occidentale performed better than the other species in terms of biomass allocation to shoots. Similarly, the effects of large trees on understory forage varied with tree species. Forage mass under T. grandis was suppressed in comparison to A. occidentale. Conversely, forage digestibility was lower under A. occidentale than under T. grandis. Finally, while forage botanical composition was uniform (with a greater proportion of grass) under T. grandis across distances from tree stem, under A. occidentale, proportions of botanical composition were more varied and comprised more legume than grass.
These results can be used for development of recommendations and guidelines on tree species selection, planting configuration, grazing, weeding, and forage management for successfully integrating silvopastoral systems into smallholder pastures in Panama.