Organic Carbon and Physical Properties in Sandy Soil after Conversion from Degraded Pasture to Eucalyptus in the Brazilian Cerrado

Abstract

Soil is currently seen as the most relevant carbon sink and the most effective carbon stabilizer. In contrast, agriculture is the second largest C emitter, after burning of fossil fuels. This organic carbon (OC) introduced into the soil, mainly via organic matter (OM), is essential for several soil properties and plays an extremely important role in sandy soils. The objective of this study was to describe the changes in the amounts and pools of OC and the influence thereof on some physical soil properties in areas converted from pasture to eucalyptus. The following areas were analyzed: a degraded pasture (PAST), two areas of pasture-eucalyptus conversion after 2 and 15 years (EU02 and EU15, respectively) and a preserved Cerrado area (CER) in the east of the state of Mato Grosso do Sul. Soil samples were taken from the 0.00-0.05, 0.05-0.10, and 0.10-0.30 m layers. The OC was measured and analyzed, the carbon pool (CP) calculated, aggregate stability, bulk density (BD), and macro-and microporosity determined, and total porosity (TP) calculated to analyze the influence of land use on soil properties. The experimental design was completely randomized, and four clusters per area were established, with nine subsampling points, for a total of 36 subsamples per area, organized in 20 × 20 m grids, The soil under natural vegetation (preserved Cerrado) was used as a control. The change from CER to commercial cultivation accelerates the process of OC loss (reductions of 25-35 %) and reductions in soil physical quality. In the PAST area, OC was reduced by 30 % in the 0.00-0.05 m layer. Cumulative OC and CP were highest in the 0.00-0.05 m layer and decreased in the deeper layers in all land use treatments. Organic C in the 0.10-0.30 m layer was not influenced by land use, indicating the possibility of OC persistence in the soil for longer periods. Macroporosity and total porosity may be considered appropriate in CER and EU15, whereas the conditions for plant development in PAST and EU02 were restrictive. Land use systems reduced OC and the CP, indicating anthropogenic disturbance of the soil compared to CER. Fifteen years after planting eucalyptus in the pasture area, signs of recovery of some soil physical properties were observed, e.g., reduced BD and increased TP.

Forest harvest management systems and residual phytomass affecting physical properties of a sandy soil

“…The TOC and CS content found in the uppermost soil layer (Table 1) is related to the input of residual phytomass from eucalyptus harvest, a recurrent response frequently reported in the literature (Costa Jr et al, 2012;Guan et al, 2015;Jesus et al, 2015;Marques et al, 2016;Sena et al, 2017). Below the surface, the increases observed in TOC and CS in deeper layers (0.20-0.60 m -Table 1) for the CTL and B coincide with the layer of greatest abundance of the root system in eucalyptus.…”

“…In a study on sandy soil, Soares et al (2017) found changes of greater magnitude in carbon stocks in the organic matter fractions in the 0.00-0.10 m soil layer due to the large contribution of the eucalyptus residual phytomass. The organic fraction of the soils do not have the same stability as the mineral fraction under agricultural use; thus, intensive use of the soil can contribute to its degradation (Six and Paustian, 2014;Sena et al, 2017), compromising the stability of its aggregates. Consequently, losses of TOC occur, which increases soil bulk density and reduces total porosity.…”

Atributos Físicos Do Solo Em Um Sistema Silvipastoril Com Núcleos Arbóreos No Estado De Santa Catarina

“…Manejos não-conservacionistas do solo, sob áreas de pastagem, podem promover a degradação da estrutura física, permitir a erosão, reduzir a macroporosidade e a infiltração de água, aumentar a resistência do solo à penetração de raízes, reduzir o volume total de poros do solo e promover erosão laminar (Byrnes et al, 2018;Brizzi et al, 2019). Estes processos acarretam no aumento da densidade do solo (Ds) e no menor desenvolvimento de macroagregados, culminando em uma contínua diminuição da produtividade (Sena et al, 2017). Entretanto, sistemas de manejo conservacionistas podem reverter este processo e melhorar os atributos físicos do solo, tais como a agregação e a Ds (Comin et al, 2016;Martinkoski et al, 2017).…”

Impact of soil use on aggregate stability and its relationship with soil organic carbon at two different altitudes in the Colombian Andes

“…Changes in soil use, from natural forest to agricultural use, frequently generate modifications in the soil organic carbon content. This affects the aggregates and soil stability directly, which leads to soil productivity loss (Sena et al, 2017). According to Lozano et al (1997), the soil structure and stability of aggregates are the most deteriorated physical properties in agricultural tropical soils that are exposed to intense conventional tillage.…”