Soil physical quality responses to silvopastoral implementation in Colombian Amazon

Abstract

Cattle ranching is the main land use after deforestation in Amazon region of Colombia. Those poor-managed pasture system typically induces soil compaction, acidification, organic matter losses and soil erosion, leading to soil health degradation and ecosystem service losses. To mitigate this problem, alternative production systems such as silvopastoral systems, where trees, forage, and cattle are combined in an integrated and intensively managed system, have been established in the last years. Hence, we conducted a field study that aimed to assess soil physical quality changes due to the traditional management of livestock and the subsequent transition to a silvopastoral system in two sites in Caquetá state, northwestern Colombian Amazon. In each site, soil samplings were performed in a chronosequence conformed by three areas following the typical land-use change at the region: i) native vegetation, ii) traditional pasture and iii) silvopastoral system. The soil physical properties quantified were: soil bulk density, porosity, penetration resistance, visual evaluation of soil structure, aggregate stability as well as soil organic carbon. Compared to native vegetation, traditional pasture management causes a degradation in soil physical quality, with increases in soil bulk density in subsoil from 1.10 to 1.33 g cm−3 and penetration resistance, which reached values around 5 MPa, affecting the distribution of pores and soil structural quality. When pastures were replaced by silvopastoral systems, we observed a recovery in the physical soil attributes with bulk density reaching values of 1.09 g cm−3 and penetration resistance of 3.77 MPa. Those improvements as well as the enhacement in visual evaluation soil structure could be associated with increases in soil C content since diversified and greater above and belowground biomass production are expected, as well as improved animal/pasture management. Thus, the implementation of silvopastoral systems is highlighted as an efficient strategy to restore soil physical quality of degraded pastures, contributing to increase pastureland productivity, and indirectly decrease deforestation pressure in the Amazon Basin.