Soil microstructure alterations induced by land use change for sugarcane expansion in Brazil

Abstract

Land use change (LUC) alters soil structure and, consequently, the functions and services provided by these soils. Conversion from extensive pasture to sugarcane is one of the largest land transitions in Brazil as a result of the growth of the domestic and global demands of bioenergy. However, the impacts of sugarcane expansion on the soil structure under extensive pasture remains unclear, especially when considering changes at the microscale. We investigated whether LUC for sugarcane cultivation impacted soil microstructure quality. Undisturbed soil samples were taken from two soil layers (0–10 and 10–20 cm) under three contrasting land uses (native vegetation—NV, pasture—PA and sugarcane—SC) in three different locations in the central‐southern Brazil. Oriented thin sections (30 μm) were used for micromorphological analysis. The total area of pores decreased following the LUC in the following order: NV > PA > SC in both soil layers. The area of large complex packing pores (>0.01 mm²) also decreased with the LUC sequence: NV>PA>SC. Qualitative and semi‐quantitative micromorphological analysis confirmed porosity reduction was driven by the decrease in complex packing pores and that biological features decreased in the same LUC sequence as the quantitative parameters. Therefore, LUC for sugarcane expansion reduced microscale soil porosity, irrespectively of soil type and site‐specific conditions, indicating that the adoption of more sustainable management practices is imperative to preserve soil structure and sustain soil functions in Brazilian sugarcane fields.

Linking Soil Water Changes to Soil Physical Quality in Sugarcane Expansion Areas in Brazil

“…First, conventional soil tillage used at land conversion breaks soil aggregates [39], leading to increased soil C oxidation to the atmosphere [38,40]. Secondly, after conversion of external drivers such as soil compaction due to continuous cattle trampling, this negatively influences the soil structure [9,17], water movement [10], and consequently, important ecosystem services, such as grass productivity, soil biodiversity and C sequestration [11], and erosion control. Therefore, the poor soil structure in PA and reduced vegetation cover in poorly managed pastures make the soil more susceptible to runoff [41] and soil erosion [39], mainly in months with higher precipitation, i.e., from October to March in the studied region (Figure 1).…”

Alluvial Soil Quality Indicators As Affected By Different Land-Uses. مؤشرات جودة التربة الطمييه تحت تأثير الاستخدامات المختلفة للأراضي.

“…Previous studies indicated that changes in soil uses from native plants to pasture to sugarcane plantation degraded soil microstructure, decreased soil porosity and negatively affected soil pores and particle size distribution, regardless of soil texture and the environmental conditions of the investigated regions (Canisares, et al, 2020). It is well confirmed that land use changes (LUC) alter soil structure and texture and accordingly, soil functionalities and services (Canisares, et al, 2020;Jimenez et al, 2020). The shift from extensive pasture to sugarcane production is one of the largest land-based shifts in Brazil because of the growth of the global and national needs of biofuels.…”

“…The shift from extensive pasture to sugarcane production is one of the largest land-based shifts in Brazil because of the growth of the global and national needs of biofuels. Hence, largescale land use changes (LUC) to expand sugarcane production in Brazil have reduced soil microporosity, regardless of the site-specific conditions and soil type, signifying that implementation of more reliable management practices is imperious to preserve soil structure and sustain soil health in sugarcane fields (Canisares, et al, 2020;Jimenez et al, 2020;.…”

“…Rengasamy and Marchuk (2011) suggested a new index of soil structural and aggregate stability termed CROSS (Cation Ratio of Soil Structural Stability), to denote the effects of Na + , K + , Mg 2+ , and Ca 2+ on soil structural stability. In addition, CROSS is also used to demonstrate the dispersive powers of Na + and K + versus the aggregating powers of Ca 2+ and Mg 2+ , but its influence on different soils under different agricultural practices and climate and relevant soil structural properties needs to be also validated (Canisares et al, 2020).…”

Challenges and approaches in assessing the interplay between microorganisms and their physical micro-environments

“…This was especially marked following the addition of glucose, which elevated the rate of microbial respiration. It is also possible to gain some insight into soil structure by dissecting and analysing cross/thin sections of soil [7] . Thin sections are typically obtained by impregnating a soil with synthetic resin and then cutting with a diamond-tipped blade following a curing period prior to polishing.…”