Agrosilvopastoral Systems and Well-Managed Pastures Increase Soil Carbon Stocks in the Brazilian Cerrado
2020
Freitas, Igor Costa de | Ribeiro, Juliana Martins | Araújo, Nayara Christina Almeida | Santos, Marcia Vitória | Sampaio, Regynaldo Arruda | Fernandes, Luiz Arnaldo | Azevedo, Alcinei Mistico | Feigl, Brigitte Josefine | Cerri, Carlos Eduardo Pellegrino | Frazão, Leidivan Almeida
Agrosilvopastoral systems have been promoted as sustainable models that combine crops, livestock grazing, and forestry in the same area. We hypothesize that agrosilvopastoral systems can improve soil C and N stocks over time. Therefore, in this study, we aimed to evaluate the changes in soil C and N stocks after conversion of low-productivity pasture into well-managed pasture and agrosilvopastoral land in the Brazilian Cerrado. Soil samples were collected in 2016 and 2018 at 0–5, 5–10, 10–20, and 20–30 cm depths from the following areas: integrated crop-livestock-forest (ICLF), marandu grass (Brachiaria brizantha) monoculture (MAR), low productivity pasture of signal grass (Brachiaria decumbens) monoculture (PAST), and native vegetation (NV; “Cerrado”). The C and N content and stocks, ¹³C natural abundance, and C contents in the physical and chemical fractions of soil organic matter (SOM) were measured. The ICLF and MAR systems promoted faster recovery of soil C and N stocks at all soil depths compared with PAST. The C content of the free light fraction of SOM under the ICLF and MAR systems increased, reaching values similar to NV up to 20 cm. The C content was higher in the humin fraction at all depths in all areas, and for this measurement, the ICLF system performed remarkably compared with PAST at a depth of 5−10 cm. Our findings support the hypothesis that conversion of low-productivity pasture into agrosilvopastoral and actively managed pasture systems leads to improvements in soil quality and C and N stocks in the Brazilian Cerrado.
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