Silvopastoral systems in the western Chaco región, Argentina

Abstract

The Chaco region is a vast plain extending over northwestern Argentina,Bolivia and Paraguay. Over the years, the woody component has increased inall vegetation communities of the Chaco. This poses a major problem forgrassland productivity because the woody plants compete for resources withgrass, impact advanced tree regeneration, hamper livestock and personnelmovements, and restrict accessibility for forage due to high stem density andthorns. These disadvantages far outweigh the advantages offered by suchtrees and shrubs in terms of providing shade, foliage and fruits, and improvingsoil conditions. To address this issue, a silvopastoral system called ?Lowintensity roller-chopping? (RBI) was tried, based on theoretical approachesand fi eld research, in the western Chaco from 1990 to 2014. A distinctivefeature of the system is that trees that are already present in the Chaco systemare mechanically disturbed by properly adjusting the size of the tractor andthe roller-chopper and regulating the frequency and severity of the number ofpasses over the standing vegetation. The operation is based on an appropriatesoil and vegetation inventory of the area at a scale >1:50,000. By using RBI,the estimated improvement of stocking rate is 3?5 ha*animal units −1 (Animalunit (AU): forage of average quality consumed by a cow of 350 kg liveweightweaning one calf a year) when native species are considered, and if Panicumspecies are used there is average increase of 1?2 ha*AU −1 . Effects on soilquality as assessed by soil organic matter (SOM); and soil nitrogen (N) mag-nitudes, tree regeneration, vegetation and bird diversity, and brush controlwere also studied. Results indicate that RBI is a promising approach to managingnative vegetation of the Chaco in a sustainable manner.