Soil carbon stock potential in pastoral and silvopastoral systems in the Peruvian Amazon

Authors: SALAZAR, ROSARIO - La Molina National Agrarian University; ALEGRE, JULIO - La Molina National Agrarian University; PIZARRO, DANTE - University Of Wisconsin; Duff, Alison; GARCIA, CARLOS - La Molina National Agrarian University; GOMEZ, CARLOS - La Molina National Agrarian University

Submitted to: Agroforestry Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2024
Publication Date: 3/20/2024
Citation: Salazar, R., Alegre, J., Pizarro, D., Duff, A., Garcia, C., Gomez, C. 2024. Soil carbon stock potential in pastoral and silvopastoral systems in the Peruvian Amazon. Agroforestry Systems. https://doi.org/10.1007/s10457-024-00969-w.
DOI: https://doi.org/10.1007/s10457-024-00969-w

Interpretive Summary: Silvopasture is the integration of trees and grazing livestock in the same agricultural system. There is limited research evaluating how silvopastoral systems may affect soil conditions, including carbon storage potential, in the Amazon. We compared soil carbon storage and other soil outcomes on 22 private farms in the San Martin region of Peru. Half of the farms were classified as traditional pastoral systems, and half were silvopastoral systems (defined as having tree cover exceeding 15% of the pasture area). Although the silvopastoral systems had greater soil carbon stocks at soil depths of 0-15 cm and 15-30 cm, these differences were not statistically significant. Soil moisture was greater and compaction was lower in silvopasture than traditional pasture, however these differences were also not significant. These results indicate silvopasture systems may have potential for greater soil carbon storage and improved soil health outcomes, but further research is needed.

Technical Abstract: Research evaluating the impact of silvopastoral systems on physical and biological properties of Amazonian soils is scarce. Thus, this study aimed to compare the soil carbon storage potential and physical and chemical soil properties of silvopastoral systems (SPS) and conventional pastoral systems (CPS) in the San Martin region of Peru. Using the Walkley and Black method, we analyzed soil organic matter at two different depths (0-15 cm and 15-30 cm). In addition, bulk density, soil moisture, total porosity, and mechanical resistance were measured in both systems. The highest (P < 0.05) carbon stocks were reported at 0-15 cm of depth with values of 31.4 Mg ha-1 and 34.4 Mg ha-1 for CPS and SPS, respectively. At 15-30 cm depth, the total carbon stock was higher for SPS, with 29.12 Mg ha-1, than for CPS, which had 26.4 Mg ha-1. Despite the absence of statistically significant differences, soil carbon stocks were higher in SPS. No significant differences in soil moisture were found between systems, although soil moisture was slightly greater in SPS than CPS (28% and 25%, respectively). The CPS had 59% of the total porosity, which was higher than the SPS. Mechanical resistance was lower in SPS (2.15 kg/cm2) than in CPS (2.33 kg/cm2) at 10 cm of depth. These results indicated that the SPS has the potential to store more carbon and improve physical and chemical traits in the soil than the CPS.