In agricultural production systems soil organic matter (SOM) is of paramount importance when assessing soil quality. Therefore, the objective of this study was to quantify the total organic carbon (TOC) and the humic fractions of the soil organic matter in silvopastoral system (SS) and to compare them with the conventional pasture system (CP) and a native vegetation area of Cerrado (NV). In the SS, soil samples were collected at distances 2.5, 5.0, 7.5 and 10 m from the eucalyptus row. Soil samples in each system were collected in the 0-10, 10-20 and 20-30 cm layers. The following parameters were determined: TOC, organic carbon associated with minerals (OCam), particulate organic carbon (OCp) and carbon of the humic soil substances. Carbon management index (CMI) and the sum of humic substances (SHs) were also calculated. SS was able to promote larger increases in the TOC, OCam and carbon stocks in the humic fractions when compared to CP and was also able to increase OCp and CMI values in depth. Soil sampling distances in the silvopastoral system had no significant influence on the changes in total carbon stocks and short-term SOM fractions. Furthermore, the land use with two years of SS implementation is not yet able to provide for most of the evaluated attributes with values equal to or higher than the soil with NV.

Canafistula seeds have a naturally slow and irregular germination due to tegument impermeability. In this study, the efficacy of nonchemical methods was investigated to break the tegument dormancy and enhance the germination rate of canafistula [Peltophorum dubium (Spreng.) Taub. -(Fabaceae)] seeds. A completely randomized design with eight treatments of seed dormancy breaking and four replications of 25 seeds each was used. Different methods to break the seed dormancy were compared: T1: untreated seeds to break dormancy (control); T2: sanding; T3: soaked in hot water (95 o C) and cooled for 24 hours; T4: pre-soaking in boiling water (100 °C) for 5 minutes; T5, T6 T7 and T8: seeds exposed to dry heating in an oven at 40 °C for 24, 48, 72 and 96 hours, respectively. All seeds were germinated in sand, and kept in a greenhouse conditions for 25 days. The emergence capacity, emergence rate index, plant growth rate, dry matter partitioning into roots and shoots, and vigor index of canafistula seedlings were measured. Mechanical scarification (sanding) and soaking in hot water (95 o C) and cooled for 24 hours were efficient to breaking the tegument dormancy and enhanced the seed emergence rate and vigor of Peltophorum dubium (Fabaceae) seedlings.

The silvopastoral system (SPS) stands out as an agroecological production system that has improved the soil's chemical quality. However, these chemical properties may have distinct changes with greater or lesser distances from the tree row tracks of the silvopastoral system. The objective of this study was to investigate the effects of the distance of the soil sampling points from the eucalyptus tree rows in a 2-year silvopastoral system on acidity components and oxidizable organic carbon fractions of the soil, as well as to compare these chemical properties with the conventional pasture system and native Cerrado vegetation. In the silvopastoral system (SPS), the soil samples were collected at 2.5, 5.0, 7.5, and 10 m of transverse distance from the eucalyptus tree row tracks. Soil samples collected in a conventional pasture area (CP) and a native Cerrado vegetation area (NV) were used as reference treatments. Soil samples were collected at depths from 0.0–0.10, 0.10–0.20, and 0.20–0.30 m. The acidity components (pH, Al3+ and H + Al) and oxidizable organic C fractions (F1: labile fraction; F2: moderately labile fraction; and F3: poorly labile fraction) were determined. The results showed that the lowest soil acidity level was observed at 2.5 and 10.0 m distances from the eucalyptus tree rows. However, the spatial distribution of soil sampling points to the eucalyptus tree rows in a 2-year silvopastoral system did not change the oxidizable fractions of the soil organic carbon. The 2-year silvopastoral system and native Cerrado vegetation area had the highest concentrations of organic carbon in the labile (F1) and poorly labile (F3) fractions in the soil profile compared to the conventional pasture system. A 2-year silvopastoral system in a low fertility tropical soil from the Brazilian Cerrado has not yet been able to improve the soil's chemical quality; therefore, further research should be carried out to investigate the medium and long-term effects of the silvopastoral system on the acidity components and oxidizable organic carbon fractions of the soil.