Abstract
Silvopastoral systems (SPS) are presented as an alternative for the protection and recovery of soils; however, the relationship between the tree component and the physical-chemical characteristics of the soil is unknown. Thus, the objective of this study was to evaluate the physical-chemical characteristics of the soil under four silvopastoral systems (SPS), alder (Alnus acuminata), pine (Pinus patula), cypress (Cupressus macrocarpa), and pona (Ceroxylon quindiuense), and a treeless system (TS) in the Amazonas region. A completely randomized design (CRD) with five treatments and three replicates was used. The experimental units were sampled at two depths, 0–15 and 15–30 cm. The parameters evaluated were pH, electrical conductivity (dS/m), organic matter (%), phosphorus (ppm), potassium (ppm), cation exchange capacity (meq/100 g), porosity (%), mechanical resistance (kg/cm2), bulk density (gr/cm3), moisture (%) and total carbon (t/ha). The results were analyzed by analysis of variance (α = 0.05 %) and Tukey's test of means (p ≤ 0.05). The systems presented strong acidic pH values (4.11–5.61), which resulted in high organic matter contents in all systems (6.74–9.99 %). The highest phosphorus content was in the SPS with alder (12.64 ppm), and the highest potassium content was in the SPS with cypress (382.33 ppm). Porosity in all systems was higher than 60 %. The highest bulk density was between 15 and 30 cm, and the highest percentage of moisture was in the surface layer (0–15 cm). The mechanical strength was higher in the SPS with cypress (2.62 kg/cm2). For all the systems evaluated, the highest carbon stock was found in the first 15 cm. The SPS with pine had the best soil characteristics and carbon sequestration (149.05 t/ha).
Highlights
In Latin America, one of the main factors causing land use changes is extensive livestock farming due to increasing deforestation when establishing new pastures (McGroddy et al, 2015)
The results of the present study were similar to those reported in Colombia from farms planted with Brachiaria humidicola associated with 3 tree species: Anadenanthera peregrina, Pithecellobium guachapele and Acacia mangium, recording acidic pH values ranging from 4.7 to 5.2 (Paez et al, 2014)
In Costa Rica, Rojas et al (2009) recorded pH values above 6.7 in six silvopastoral systems based on the combination of Brachiaria brizantha and Hyparrhenia rufa with native timber species in the dry tropics
Summary
In Latin America, one of the main factors causing land use changes is extensive livestock farming due to increasing deforestation when establishing new pastures (McGroddy et al, 2015) This scenario has raised the need to implement various actions that can promote the development of sustainable livestock farming, such as an alternative to encourage the natural regeneration of vegetation and the conservation of forests in the installation of silvopastoral systems (Arciniegas-Torres and Florez-Delgado, 2018). The total carbon stock in the biomass in this area could be up to 10.9 billion tonnes of carbon (Ministry of Environment, 2014; Food and Agriculture Organization, 2016) These resources are not well managed, and high rates of deforestation are recorded, causing soil degradation that affects crop production and environmental sustainability (Rojas et al, 2019). During the 1990–2015 period, the deforested area was 12 399 577.08 ha, which represents 12 % of the Amazon forest area, and the Amazon region has a deforested area of 1 010 590.75 ha (Ministry of Environment, 2015)
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