Carbon/nitrogen ratio in soils of silvopastoral systems in the Paraguayan Chaco

Abstract

The silvopastoral system renders the livestock production more sustainable because the interaction between its components brings benefits to the soil, to the grassland, livestock and trees; furthermore, it enhances the productivity and the diversification of production. To know the characteristics of these systems, a study was carried out in private properties located in the Paraguayan Chaco, where eight permanent plots of 1 ha each were established in which all Prosopis spp. (carob) individuals were measured and identified, and samples were drawn from grasslands of subplots located beneath the canopy of the trees and beyond to compare their biomass; soil samples were also obtained under the same conditions, at two different depths —0 to 10 cm and 10 to 30 cm— with the purpose of comparing the content of organic matter and carbon/nitrogen ratio (C/N). The arboreal component consisted of Prosopis alba (white carob tree) and Prosopis nigra (black carob tree), in association with cultivated grassland composed mostly by Panicum maximum cv Gatton panic (Gatton Panic), Digitaria decumbens (Pangola grass), and Cenchrus ciliaris (Buffel grass). The presence of the carob trees influenced the biomass of the grassland, which was more abundant beneath the tree crowns than outside of them. The organic matter in the soil exhibited no significant differences between the conditions of sun and shade, but it differed between depths; in contrast, the C/N ratio did not change under any of the conditions.